Next Article in Journal
The Influence of Internal Geometry on Pressure Losses, Hydraulic Stability, and Cavitation Risk in a Firefighting Monitor
Previous Article in Journal
BPA-STGCN: Body-Part-Aware Spatio-Temporal Graph Convolutional Network for Stable Skeleton-Based Action Recognition
Previous Article in Special Issue
Damage Evolution and Energy Dissipation Mechanism of Sandstone Subjected to Freeze–Thaw Action: Effects of Moisture Conditions
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Applied Sciences
Volume 16
Issue 17
10.3390/app16178733
applsci-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Dynamic Sliding Behavior of Sand-Filled Rock Joints Under Impact Loading: Evolution of Particle-Size Effects

by
Chao Wei
1,†,
Zhu Song
1,†,
Shuxin Deng
1,
Chenkang Liu
2,* and
Zhuorui Wu
1,*
1
School of Safety Science and Engineering (School of Emergency Management), Nanjing University of Science and Technology, Nanjing 210094, China
2
School of Safety Science and Engineering, Anhui University of Science and Technology, Huainan 232001, China
*
Authors to whom correspondence should be addressed.
†
These authors equally contributed to this work.
Appl. Sci. 2026, 16(17), 8733; https://doi.org/10.3390/app16178733
Submission received: 9 August 2026 / Revised: 30 August 2026 / Accepted: 31 August 2026 / Published: 2 September 2026
(This article belongs to the Special Issue Recent Advances in Rock Mass Engineering: 2nd Edition)
Browse Figures
Versions Notes

Abstract

Blocky-rock masses are prone to dynamic slip along sand-filled joints under impact disturbance. The constraint normal to the joint and the size of the infill particles jointly influence their stability. To determine how axial load and particle-size affect dynamic slip, this study uses a custom-developed dynamic slip testing system for blocky-rock masses. Impact-disturbance tests are conducted under a constant lateral shear load with different axial load values and quartz-sand particle sizes. The block displacement evolves through three stages: stationary incubation, rapid slip, and deceleration to a stable state. When the axial load increases from 100 N to 400 N, residual slip displacement decreases by 87.52% to 90.12% across the particle size conditions. Residual slip displacement also follows an exponential decay with increasing axial load. Reducing particle size decreases both slip velocity and residual slip displacement, but its influence gradually weakens as the axial load increases. The difference in residual slip displacement between the coarse and fine particle conditions narrows from 0.460 mm to 0.030 mm. Strengthening the normal constraint compacts the granular layer and restricts particle movement, causing the dynamic slippage at sand-containing structural interfaces to gradually shift from being significantly influenced by the particle scale to being primarily controlled by the normal constraint.

1. Introduction

Deep underground engineering and resource extraction are commonly conducted under high in situ stresses and intense dynamic disturbances, under which slip instability along rock joints constitutes a major trigger of dynamic hazards, including slip-type rockbursts [1,2,3,4]. Natural rock masses are divided by networks of geological joints, including joints, faults, and bedding planes, into discrete blocks, thereby forming blocky-rock masses. Established rock mass classification and characterization systems, including the Rock Mass Rating (RMR), Geological Strength Index (GSI), and Q-system, provide complementary frameworks for characterizing the geological and mechanical quality of jointed rock masses. In particular, the Q-system combines rock quality designation and joint set number, joint roughness and alteration, and joint water and stress reduction factors, emphasizing that rock mass behavior cannot be represented by a single joint or infill parameter [5,6]. As mechanically weak interfaces characterized by relatively low strength and localized deformation, rock joints directly govern the relative motion between adjacent blocks and the overall stability of the rock mass through their contact conditions and slip resistance [7,8,9,10,11,12,13]. Field evidence from deep South African mines and the deeply buried tunnels of the Jinping-II Hydropower Station indicates that shear rupture along pre-existing planes of weakness or newly formed rupture surfaces, together with structural-plane-controlled rockburst development, represents an important dynamic failure mode in deep rock masses [14,15]. Characterizing the evolution of slip displacement along rock joints under dynamic disturbances is therefore essential for understanding the instability mechanisms of deep blocky rock masses.
At the field scale, the mechanical behavior of a fractured rock mass is governed collectively by joint dip and dip direction, the number and orientation of joint sets, joint spacing and persistence, joint roughness, joint aperture, degree of weathering or alteration, hydrogeological conditions, and the magnitude and orientation of the in situ stress field [16,17,18,19,20,21,22]. These factors collectively influence block kinematics, stress distribution along potential sliding surfaces, and the hydro-mechanical response of joint networks, and should therefore be considered when extrapolating laboratory observations to field-scale fractured rock masses. Natural rock joints are not ideally smooth contact interfaces; they commonly contain infill materials such as fault gouge, breccia, mineral fragments, and sand-sized particles. Joint infill can range from clay-rich or cemented materials with appreciable cohesion to nominally cohesionless granular materials whose shear resistance is governed predominantly by friction, particle rearrangement, and interlocking. The presence of granular infill transforms joint shear behavior from simple rock–rock friction into a composite rock–particle–rock interaction. The physicomechanical properties, particle morphology, packing state, and particle-size distribution of the infill can all influence the interfacial shear strength, deformation characteristics, and energy-dissipation processes [23,24,25,26,27,28,29,30]. Under excavation blasting, mining-induced disturbances, and associated vibrations in deep engineering, infilled joints are more susceptible to transient weakening of slip resistance and cumulative slip, potentially destabilizing the surrounding rock blocks. The effects of infill particle properties on the dynamic slip behavior of rock joints therefore warrant particular attention when evaluating the stability of deep blocky-rock masses.
Previous studies of dynamic slip along rock joints have examined the effects of coupled static-dynamic loading, surface roughness, normal stress, loading rate, and cyclic disturbance [31,32,33,34,35,36]. Lang [37] and Li [38] characterized the responses of joint infill and rock joints to impact disturbance from the perspectives of dynamic response and energy dissipation, respectively. Using impact direct-shear testing systems, Wang [39,40] investigated the slip response and changes in the shear load-bearing capacity of rough rock joints under high loading rates and intense impact disturbances. Physical model tests on blocky-rock masses conducted by Deng [41] revealed that impact disturbance can dynamically unload the normal stress acting on a joint, thereby inducing slip instability. Li [42] further demonstrated that the coupled action of low confining pressure and impact disturbance weakens the slip resistance of rock joints. Although these studies have provided an important basis for understanding dynamic instability along rock joints, they have focused primarily on the dynamic shearing of rough joints, responses to coupled static-dynamic disturbances, and the mechanisms of block-slip instability. The evolution of slip displacement along granular-filled joints under the coupled effects of varying normal constraint and impact disturbance remains insufficiently understood.
At the particle scale, the infill not only contributes to interfacial load transfer and energy dissipation, but can also alter the slip mode of a joint through particle rolling, rearrangement, wedging, and crushing. Liu [43] reported that coarse-grained infill can enhance the energy-dissipation capacity of rock joints within a certain particle-size range. Repeated-impact tests conducted by Wang [44] demonstrated that the moisture content and impact-induced compaction of clay infill modify the normal stiffness of filled rock joints. Other studies have shown that particle angularity can improve interfacial frictional stability through mechanical interlocking [45]. However, extensive attention has been paid to infill type, infill thickness, particle morphology, and saturation state. In contrast, particle size, a critical microscale parameter under single-mineral infill conditions, has been largely neglected. For quartz-sand-filled joints in particular, particles of different sizes may differ in their propensity for rolling, rearrangement, wedging, and crushing under impact disturbance, thereby affecting the slip displacement and post-slip equilibrium state of the joint. Quasi-static direct-shear tests have shown that the shear strength of particle-filled joints varies with particle size [46], but whether this relationship persists under combined normal constraint and impact loading remains unclear. Furthermore, increasing axial load alters both the packing state of the granular infill and the interfacial contact state. Whether these changes amplify or suppress the effect of quartz-sand particle size on joint slip displacement therefore requires further investigation.
Based on the considerations outlined above, the present study focuses on rock joints filled with quartz sand, which is treated as a nominally cohesionless granular material whose shear resistance is governed predominantly by friction, particle rearrangement, and interlocking, in contrast to clay-rich, cemented, or other cohesive joint infills. A dynamic slip test model with composite sand-rock interfaces was constructed using a custom-developed impact-disturbance apparatus for blocky-rock masses, and impact tests were conducted under different combinations of axial load and quartz-sand particle size. By controlling the joint configuration, infill placement, lateral shear load, and impact intensity, the experiments were designed to investigate the effects of normal constraint and particle size on the dynamic slip behavior of sand-filled joints. The central scientific question is how the slip displacement of a sand-filled joint varies with axial load and quartz-sand particle size under impact disturbance, and how increasing normal constraint influences the particle-size effect. The experimental model necessarily simplifies the conditions of natural fractured rock masses; therefore, the results primarily characterize the dynamic slip behavior of the specific quartz-sand-filled joint configuration considered here, and their extension to natural rock masses with complex joint geometries, hydrogeological conditions, and in situ stress states requires further validation. The results provide an experimental basis for understanding the dynamic slip mechanisms of granular-filled joints and the slip instability of deep blocky-rock masses.

2. Experimental Program

2.1. Test Apparatus

The impact-disturbance testing apparatus for blocky-rock masses used in this study was independently designed and developed by the research team, and its principal components and weight-controlled lateral shear-loading arrangement are shown in Figure 1. The apparatus was designed to simulate dynamic disturbance conditions relevant to underground engineering and to investigate the impact-induced sliding response of a constrained block separated by sand-filled interfaces. It comprises an axial loading system, an impact-disturbance system, a blocky-rock model frame, and a high-frequency data-acquisition system.

2.1.1. Axial Load and Lateral Shear-Loading System

The axial load and lateral shear-loading system comprises a high-stiffness reaction frame, hydraulic jacks, a steel cable, a low-friction pulley, and a suspended-weight assembly. The hydraulic jacks operate under force control and apply seven axial load levels of 100, 150, 200, 250, 300, 350, and 400 N, reported as the axial forces recorded directly by the loading system. The selected range allows the rock blocks to remain in a stable and controllable compression–shear state before impact, while the 50 N increments provide sufficient resolution to distinguish changes in the impact-induced slip response. Within this range, increasing axial load strengthens the normal constraint on the sand-filled joints and is therefore expected to suppress impact-induced slip more effectively. For lateral shear loading, a hook fixed to the side of target block B2 is connected to the suspended-weight assembly by a steel cable routed over the low-friction pulley, as shown in Figure 1. The weight-induced cable tension is redirected by the pulley into a constant lateral shear load acting on B2 in the prescribed slip direction. This load provides the static driving force for block slip and, together with the axial load, maintains B2 in a stable compression–shear equilibrium state before impact disturbance. Together, these loads represent the combined compression–shear loading state of rock joints.

2.1.2. Impact-Disturbance System

The impact-loading system operates through high-pressure gas propulsion and consists primarily of an air compressor, a solenoid valve, a launch tube, and a custom-designed projectile. During each test, compressed gas is rapidly released from the air compressor to propel and accelerate the projectile through the launch tube. A photoelectric-gate sensor installed at the end of the tube measures the instantaneous projectile velocity immediately before impact. Rubber pads are also placed at both the impact-facing and distal ends of the block assembly to suppress stress-wave reflections and alleviate transient stress concentrations during impact.

2.1.3. Blocky-Rock Model Frame and High-Frequency Data-Acquisition System

The blocky-rock model consists of eight cubic rock blocks, each measuring 100 × 100 × 100 mm, arranged in series within the axial loading frame. The contact surfaces were left unground and unpolished after cutting, and this finish was retained as the pre-shear surface condition, thereby approximating the contact characteristics of natural rock joints. Under axial load, the blocks were brought into close contact to facilitate effective stress-wave transmission. To accurately capture the propagation and evolution of stress waves through the rock blocks, mounting blocks were bonded to the surface of each block using a high-strength adhesive and served as mounting bases for the accelerometers. The high-frequency data-acquisition system comprises a DH8302 dynamic-signal testing and analysis system, a DH5863 programmable charge amplifier, and high-precision piezoelectric accelerometers, pressure sensors, and displacement transducers. The system enables real-time acquisition and recording of the dynamic-response signals from each rock block along the impact direction, providing high-fidelity data for subsequent analyses of stress-wave propagation and rock block slip behavior.

2.2. Specimens and Test Conditions

Cubic marble blocks measuring 100 × 100 × 100 mm, with an average mass of approximately 2.70 kg, were used in the tests. The identical cubic geometry and side lengths were selected to be compatible with the internal dimensions of the axial loading frame and to maintain full-face alignment between adjacent blocks. A test matrix combining four quartz-sand particle-size classes and seven axial load levels was established under a constant lateral shear load, as detailed in Table 1.
As illustrated in Figure 2, the eight rock blocks were labeled B1–B8. Block B2 was designated as the target sliding block to represent a localized slip unit controlled by two sand-filled joints. The blocks were aligned in series within the model frame, with the axial load and impact disturbance acting along the longitudinal direction of the block assembly and the constant lateral shear load acting on B2 along the prescribed slip direction. The two opposing 100 × 100 mm contact faces between B2 and the adjacent blocks defined the sand-filled joints and therefore determined the joint geometry and interface dimensions of the target sliding block. The rock surfaces forming these joints were produced by cutting, and the resulting surface condition was retained before shear loading without grinding, polishing, artificial roughening, or any other special treatment. Consequently, the interfaces used in all tests had a consistent, macroscopically planar and smooth surface condition. Impact disturbance was generated pneumatically. The driving gas pressure was maintained at 0.1 MPa in all tests, corresponding to a mean projectile impact velocity of approximately 2.7 m/s.

2.3. Experimental Procedure

The experimental procedure comprised four stages: specimen assembly and sensor installation, application of boundary conditions, system commissioning, and impact testing.
Initially, the specimens were prepared, the sensors were installed, and the loading components for the target block were positioned. An accelerometer was bonded to the geometric center of the top surface of each rock block (B1-B8) using a high-stiffness epoxy adhesive. After the adhesive had fully cured, the block assembly was installed within the loading frame. A loading hook was attached to the side of target block B2 to apply the lateral shear load. The probe of the displacement transducer was placed in firm contact with the side of B2 and slightly precompressed to eliminate any initial gap.
Subsequently, the sand-filled joints were prepared, and the axial load and lateral shear load were applied. A layer of petroleum jelly approximately 0.2 mm thick was uniformly applied to both contact faces between B2 and the adjacent rock blocks. The petroleum jelly was used solely to retain the quartz sand and prevent particle loss. Quartz sand of the prescribed particle-size class was then distributed uniformly over each entire lateral contact surface, with representative samples shown in Figure 3. For each particle-size condition, the same placement procedure was used on both sides of B2, and an equal mass of sand was applied to each interface. After B2 had been repositioned and the blocky-rock model reassembled, axial load was applied using the hydraulic servo-controlled system to close and compact the composite sand-rock interfaces. Once the axial load had stabilized, a constant lateral shear load was applied through a steel cable, a low-friction pulley assembly, and standard weights, bringing B2 into a stable combined compression–shear equilibrium state.
Thereafter, the data-acquisition system was commissioned. The acceleration, displacement, and pressure sensors were connected to form a measurement chain comprising the sensors, charge amplifier, and dynamic-signal acquisition unit. The stability of each measurement channel was verified, and the charge-amplifier gain and acquisition range were set according to the anticipated impact intensity. The photoelectric-gate velocimetry system was also calibrated to record the projectile impact velocity.
Finally, impact loading and replicate testing were performed. The driving gas pressure was stabilized at 0.1 MPa, after which the solenoid valve was triggered to propel the projectile into the blocky-rock model. The projectile velocity, acceleration of each rock block, B2 displacement, and interfacial-pressure time histories were recorded synchronously. After each test, the axial load and lateral shear load were removed. The quartz sand was then cleared and redeposited using the same procedure to reset the composite sand-rock interfaces.

3. Results and Analysis

3.1. Effect of Axial Load on Impact-Induced Block-Slip Evolution

Figure 4 shows the horizontal-displacement time histories of block B2 under impact disturbance at different axial load levels. Across all quartz-sand particle-size conditions, the block-slip response exhibits three successive stages: quiescent incubation, rapid slip, and deceleration to a stable state. Before impact, B2 remains stable and its horizontal displacement is essentially unchanged. Following impact, the displacement increases sharply as the block enters the rapid-slip stage. As the disturbance attenuates, the displacement rate progressively decreases, eventually approaching a stable residual slip displacement. The temporal evolution of block slip following impact is characterized using the displacement history, slip onset time, maximum slip velocity, and slip duration.
The displacement curves obtained at different axial load levels differ primarily in the slip onset time, duration of the acceleration stage, and final residual slip displacement. As the axial load increases, the displacement curves shift downward, their slopes during the rapid-slip stage decrease, and the final residual slip displacement is reduced. The axial load has a comparatively minor effect on the slip onset time but exerts more pronounced effects on the maximum slip velocity and final residual slip displacement. The final residual slip displacements and characteristic impact-induced slip parameters for all test conditions are summarized in Table 2 and Table 3, respectively.
As shown in Table 2, the final residual slip displacement generally decreases with increasing axial load at a given quartz-sand particle size. For the 6 to 8 mesh quartz-sand infill, the final residual slip displacement is 1.189 mm at an axial load of 100 N. As the axial load increases to 200, 300, and 400 N, the residual slip displacement decreases to 0.672, 0.266, and 0.121 mm, respectively, representing reductions of 43.48%, 77.63%, and 89.82%, relative to that at 100 N. For the 8 to 16, 16 to 26, and 40 to 70 mesh infill conditions, increasing the axial load from 100 to 400 N reduces the residual slip displacement from 0.992, 0.810, and 0.729 mm to 0.098, 0.098, and 0.091 mm, respectively, corresponding to reductions of 90.12%, 87.90%, and 87.52%. The consistent trends across the particle-size classes demonstrate that increasing axial load effectively reduces the magnitude of impact-induced block slip.
As shown in Table 3, the block-slip onset time ranges from 25.520 to 42.105 ms across the different test conditions, whereas the maximum slip velocity and slip-stage duration range from 0.0035 to 0.0423 mm/ms and from 45.192 to 97.989 ms, respectively. Compared with the slip onset time, the duration of the acceleration stage and the maximum slip velocity vary more markedly among the test conditions. This result indicates that axial load and quartz-sand particle size primarily govern the post-onset evolution of block slip.
Comparison among the different axial load intervals reveals that the residual slip displacement initially decreases rapidly with increasing axial load and then gradually approaches a plateau. Within the range of 100 to 250 N, the displacement curves for the different particle-size conditions are clearly separated, and the residual slip displacement decreases substantially. When the axial load reaches 300 to 400 N, the displacement curves progressively converge, and the absolute change in residual slip displacement becomes markedly smaller. For example, under the 6 to 8 mesh quartz-sand infill condition, increasing the axial load from 100 to 200 N reduces the residual slip displacement by 0.517 mm, whereas increasing it from 300 to 400 N produces a reduction of only 0.145 mm. Similar trends are observed for the other particle-size conditions.
Figure 5 presents the scatter plots and fitted curves showing how the residual slip displacement varies with axial load under different quartz-sand particle-size conditions. In all cases, the residual slip displacement decreases rapidly at lower axial loads and then declines at a progressively slower rate as the axial load increases. From the perspective of stress state, increasing axial load increases the normal stress acting on the interface and progressively decreases the shear-to-normal stress ratio under the constant lateral shear load. This change corresponds to the continuous attenuation of residual slip displacement with increasing axial load shown in Figure 5.
The relationship between residual slip displacement and axial load can be described by a two-parameter exponential decay function:
u r = a e ( − b N )
where u r is the final residual slip displacement; N is the axial load; a is the residual slip decay amplitude, expressed in mm, whose value reflects the potential slip magnitude obtained by extrapolating the fitted model to a state of low normal constraint; and b is the axial load coefficient, expressed in N−1, which characterizes the rate at which the residual slip displacement decreases with increasing axial load. A larger b value indicates greater sensitivity of the residual slip displacement to changes in axial load. The fitted parameters for the different particle-size conditions are listed in Table 4. As the quartz-sand fraction becomes finer, the fitted decay amplitude a decreases from 2.5052 to approximately 1.52 mm, indicating a corresponding reduction in the fitted potential slip magnitude. By contrast, b remains within a relatively narrow range of 0.006364 to 0.007194 N−1, indicating that particle size primarily affects the magnitude of the slip response, whereas axial load governs its overall attenuation rate.

3.2. Effect of Infill Particle Size on Impact-Induced Block-Slip Evolution

Figure 6 shows the horizontal-displacement time histories of block B2 for different quartz-sand particle-size classes at axial load levels of 100, 200, and 300 N. All particle-size groups exhibit a transition from the stationary state to rapid slip, followed by deceleration toward a stable state. However, the slope of the displacement curve during the rapid-slip stage and the final residual slip displacement differ among the particle-size groups.
At a given axial load, decreasing the quartz-sand particle size shifts the displacement curves downward and generally reduces both the maximum slip velocity and the final residual slip displacement. At an axial load of 100 N, the residual slip displacements for the 6 to 8, 8 to 16, 16 to 26, and 40 to 70 mesh quartz-sand fractions are 1.189, 0.992, 0.810, and 0.729 mm, respectively. When the infill particle-size class changes from the 6 to 8 mesh range to the 40 to 70 mesh range, the residual slip displacement decreases by 0.460 mm, representing a reduction of 38.69%. At an axial load of 200 N, the residual slip displacements for the four particle-size classes are 0.672, 0.558, 0.450, and 0.300 mm, respectively, with a difference of 0.372 mm between the 6 to 8 and 40 to 70 mesh conditions. When the axial load increases to 300 N, the corresponding residual slip displacements decrease to 0.266, 0.231, 0.230, and 0.193 mm, and the maximum difference among the particle-size groups narrows to 0.073 mm. These results demonstrate that the effect of quartz-sand particle size on residual slip displacement weakens as the axial load increases. During the rapid-slip stage, the displacement curves for coarse-grained infill typically rise more steeply, indicating a stronger dynamic slip response of the block following impact disturbance. As the quartz-sand particle size decreases, the displacement curves rise more gradually, while the maximum slip velocity and final displacement amplitude generally decrease. Particle size has a comparatively limited effect on the slip onset time; its influence is manifested primarily in the post-onset development of block slip.
The characteristic quartz-sand particle size d e was defined as the geometric mean of the aperture sizes of two adjacent sieves. The characteristic particle sizes corresponding to the 6 to 8, 8 to 16, 16 to 26, and 40 to 70 mesh fractions were 2.812, 1.669, 0.841, and 0.300 mm, respectively. Thus, each d e value is used as a representative particle size for the corresponding sieve fraction rather than as a descriptor of a complete continuously graded particle-size distribution. Figure 7 shows the relationship between the characteristic particle size and residual slip displacement at different axial load levels. The scatter data indicate that the residual slip displacement generally increases with increasing characteristic particle size, with this trend being more pronounced at a lower axial load.
Within the experimental range, the relationship between characteristic particle size and residual slip displacement can be described by a linear function:
u r = α d e + β
where α is the particle-size sensitivity coefficient, representing the average change in final residual slip displacement for each 1 mm increase in characteristic particle size; and β is the fitted intercept, representing the residual slip displacement predicted by the model as the characteristic particle size approaches zero.
The latter reflects the baseline slip level of the joint for an infinitesimally fine-grained infill. The fitted parameters at different axial load levels are listed in Table 5. As shown in Table 5, the particle-size sensitivity coefficient, α, decreases markedly with increasing axial load, indicating that the residual slip displacement becomes progressively less sensitive to variations in quartz-sand particle size. The goodness of fit also decreases as the axial load increases. This result indicates that, under a high axial load, the differences in residual slip displacement among the particle-size conditions become smaller and the linear dependence of residual slip displacement on particle size gradually weakens.

3.3. Slip Behavior Under the Coupled Effects of Axial Load and Particle Size

As shown in Figure 5 and Table 2, the differences in residual slip displacement among the quartz-sand particle-size conditions generally decrease with increasing axial load. To directly compare how the particle-size-dependent differences evolve across different axial load levels, the 6 to 8 and 40 to 70 mesh conditions, which represent the coarse and fine ends of the investigated particle-size range, were selected. The differences in residual slip displacement between these two conditions were calculated at representative axial load levels of 100, 200, 300, and 400 N, as summarized in Table 6. At the low axial load of 100 N, the difference between the coarse- and fine-grained infill conditions is relatively large, indicating that the block-slip response is sensitive to variations in quartz-sand particle size. At 200 N, a pronounced difference in slip displacement remains between the two particle-size conditions. When the axial load increases to 300 N, however, the difference decreases markedly, and, at 400 N, the slip responses of the two conditions become comparable.
These results demonstrate that increasing axial load not only directly reduces the residual block-slip displacement but also diminishes the differences in slip response among the quartz-sand particle-size conditions. Under a low axial load, infill particle size is an important factor governing the dynamic block-slip response. As the axial load increases, the normal constraint exerts progressively greater control, and the relative influence of the initial quartz-sand particle size correspondingly weakens.

4. Discussion

4.1. Dynamic Unloading and Slip Triggering Under Impact Disturbance

In the initial loading state, the axial load provides the normal constraint on the sand-filled joint and simultaneously influences the packing state of the quartz-sand infill, while the lateral shear load supplies the driving force for block slip, and the block remains in stable equilibrium. In soil mechanics, the packing state of granular materials is commonly characterized by the specific volume and relative density. Within this framework, increasing axial load promotes joint closure and particle rearrangement and can be understood as shifting the infill toward a state of lower specific volume and higher relative density. In stress space, as the axial load increases, the normal constraint on the interface becomes stronger while the lateral shear load remains constant; consequently, the shear-to-normal stress ratio decreases and the frictional resistance that must be overcome for relative block slip increases.
When the impact disturbance reaches the target block, differential vibration develops between the rock blocks on opposite sides of the joint, causing a transient change in the normal contact state of the interface. As the joint tends to open, the interparticle contact pressure decreases and the load-bearing force chains undergo local rearrangement, thereby weakening the frictional and interlocking resistance of the sand-filled joint. Once the instantaneous slip resistance falls below the applied lateral shear force, the block transitions from the stationary state to dynamic slip. Increasing axial load enhances joint closure and stabilizes the particle contact network, suppressing the impact-induced transient unloading effect and making the slip-triggering condition more difficult to attain. The dynamic unloading and slip-triggering process along the joint under impact disturbance is illustrated in Figure 8.

4.2. Transition from Particle Rolling to Interlocking

Quartz-sand particle size influences the dynamic slip resistance of the joint by altering the particle-contact configuration and kinematic freedom within the infill layer. The particle-motion modes and contact-network evolution under different particle-size conditions are illustrated in Figure 9. Under coarse-grained conditions, fewer particles and effective contact points contribute to load transfer per unit area, providing greater freedom for particle rolling, rotation, and force-chain rearrangement. When subjected to impact disturbance, these particle motions accommodate the induced shear deformation and facilitate relative displacement between the rock blocks. As particle size decreases, the numbers of particles and potential load-bearing contacts per unit area increase, forming a more spatially distributed multipoint contact network between the particles and joint walls and among the particles themselves. Under impact-induced shearing, relative block displacement must then overcome interparticle friction, particle interlocking, and contact-network reconfiguration.
Packing state further influences these particle-size-dependent mechanisms. A lower specific volume or higher relative density generally corresponds to more particle contacts and stronger interlocking, thereby restricting particle rolling and rearrangement. During impact-induced shearing, stronger interlocking may also induce dilatancy, contributing to a peak frictional resistance greater than the critical-state or ultimate resistance. As the particle structure is progressively reorganized, dilatancy and its contribution to shear resistance diminish. Consequently, the deformation mode of the infill layer progressively shifts from widespread particle rolling and bulk rearrangement to constrained, localized shear deformation.

4.3. Energy-Dissipation Mechanism During Dynamic Slip

The energy introduced by impact disturbance is redistributed among rock-block vibration, contact adjustment along the joint, particle-scale deformation of the infill, and block slip. Part of this energy is converted into the kinetic energy of the sliding block, whereas the remainder is transmitted or dissipated through stress-wave propagation, interfacial friction, particle collisions, rolling, rearrangement, and reconstruction of the contact network. Particle rearrangement during transient loading may locally reduce the void ratio and specific volume of the quartz-sand infill and modify the load-bearing force chains. At highly loaded local contacts, limited particle crushing may provide an additional energy-dissipation mechanism and produce smaller fragments that participate in subsequent contact-network evolution.
The packing state of the infill influences the dominant energy-dissipation mechanisms. At a comparatively large specific volume and low relative density, particles have greater freedom to roll, rotate, collide, and undergo contractive rearrangement under impact disturbance. As the specific volume decreases and the relative density increases, more particles participate in load transfer, and stronger interlocking increases the frictional work and contact-network reconfiguration required during block slip. Therefore, increasing axial load and decreasing particle size increase the number and stability of load-bearing contacts and provide more frictional energy-dissipation pathways. As the disturbance attenuates and normal contact is restored, interfacial friction, particle collisions, and repeated contact-network reconfiguration continuously dissipate the kinetic energy of the sliding block.

4.4. Mechanism Underlying the Attenuation of the Particle-Size Effect Under Enhanced Normal Constraint

Under a low axial load, the comparatively large specific volume and low relative density of the infill allow particle-size-dependent differences in particle mobility and contact-network evolution to remain pronounced under impact disturbance. Coarse particles have greater freedom to roll and rearrange, whereas the finer-particle system provides more widely distributed potential contact locations, and particle motion is more readily constrained jointly by the surrounding particles and joint walls. Consequently, the block-slip response exhibits a strong dependence on particle size.
As the axial load increases, joint closure promotes particle rearrangement and can be interpreted as an evolution of the infill toward a lower specific volume and a higher relative density. The resulting increase in load-bearing contacts and particle interlocking restricts particle rolling, rotation, and positional rearrangement, and increases the shear resistance that must be overcome for relative block displacement. For a denser granular state, stronger interlocking is generally accompanied by a greater tendency for dilation, whereas the enhanced normal constraint simultaneously suppresses the actual development of dilation. Therefore, at higher axial loads, particle kinematic freedom is more strongly constrained and the differences in particle motion among the different particle sizes gradually decrease, thereby reducing the residual slip displacement and progressively attenuating the particle-size effect.

5. Conclusions

To investigate the impact-induced sliding response of sand-filled rock joints, physical model tests were conducted using a custom-developed impact-disturbance testing apparatus for blocky-rock masses under controlled axial load, constant lateral shear load, and impact disturbance. The effects of axial load and quartz-sand particle size on the residual block-slip displacement were systematically examined. The principal findings obtained within the tested loading range are summarized as follows:
(1)
The dynamic slip response of the joint is closely related to the axial load level. Increasing the axial load strengthens the normal constraint on the joint and enhances both interfacial frictional resistance and energy-dissipation capacity, thereby markedly reducing the magnitude of block slip. As the axial load increases from 100 to 400 N, the final residual slip displacement decreases by more than 87% under all particle-size conditions. The sensitivity of the slip response to axial load is nonlinear: the residual slip displacement decreases rapidly in the low-axial-load range but gradually approaches a stable level in the high-axial-load range.
(2)
Infill particle size is a key factor governing the dynamic slip behavior of the joint. At an axial load of 100 N, decreasing the quartz-sand particle size from 6 to 8 to 40–70 mesh reduces the final residual slip displacement from 1.189 to 0.729 mm. A smaller particle size increases the numbers of load-bearing particles and contact points per unit area, thereby strengthening the constraints imposed on relative block displacement by interparticle friction, local wedging, and contact-network reconfiguration. In contrast, coarse particles are more prone to rolling and rearrangement under impact disturbance and therefore produce a more pronounced slip response.
(3)
Under coupled loading conditions, the particle-size effect is governed by the axial load level. As the axial load increases from 100 to 400 N, the difference in residual slip displacement between the 6 to 8 and 40 to 70 mesh conditions decreases from 0.460 to 0.030 mm. With increasing axial load, the infill layer becomes progressively compacted, restricting particle rolling, rotation, and positional rearrangement. Consequently, the contact states and slip responses under the different particle-size conditions gradually converge. The influence of particle-size differences on block-slip behavior is therefore pronounced under a low axial load but substantially attenuated at higher axial load levels.

Author Contributions

Conceptualization, Z.S. and C.L.; Methodology, Z.S.; Validation, C.W. and Z.S.; Formal analysis, Z.S., C.L. and Z.W.; Investigation, C.W. and S.D.; Resources, S.D.; Data curation, C.W. and C.L.; Writing—original draft, C.W.; Writing—review & editing, C.W., S.D., C.L. and Z.W.; Supervision, C.L. and Z.W.; Project administration, S.D. and Z.W.; Funding acquisition, S.D. All authors have read and agreed to the published version of the manuscript.

Funding

The work presented in this paper is supported by National Natural Science Foundation of China (Grant no. 51909120, 42102331 and 52608650). The support is gratefully acknowledged.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors are also very grateful to the reviewers for their valuable comments and suggestions.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Li, X.; Gong, F.; Tao, M.; Dong, L.; Du, K.; Ma, C.; Zhou, Z.; Yin, T. Failure Mechanism and Coupled Static-Dynamic Loading Theory in Deep Hard Rock Mining: A Review. J. Rock Mech. Geotech. Eng. 2017, 9, 767–782. [Google Scholar] [CrossRef] [Scilit]
  2. Askaripour, M.; Saeidi, A.; Rouleau, A.; Mercier-Langevin, P. Rockburst in Underground Excavations: A Review of Mechanism, Classification, and Prediction Methods. Undergr. Space 2022, 7, 577–607. [Google Scholar] [CrossRef] [Scilit]
  3. Wu, Z.R.; Xu, T.T.; Arson, C. Effect of the Intermediate Principal Stress on Pre-Peak Damage Propagation in Hard Rock under True Triaxial Compression. Rock Mech. Rock Eng. 2022, 55, 6475–6494. [Google Scholar] [CrossRef] [Scilit]
  4. Zhang, W.; Feng, X.T.; Yao, Z.B.; Hu, L.; Xiao, Y.X.; Feng, G.L.; Niu, W.J.; Zhang, Y. Development and Occurrence Mechanisms of Fault-Slip Rockburst in a Deep Tunnel Excavated by Drilling and Blasting: A Case Study. Rock Mech. Rock Eng. 2022, 55, 5599–5618. [Google Scholar] [CrossRef] [Scilit]
  5. Barton, N.; Lien, R.; Lunde, J. Engineering Classification of Rock Masses for the Design of Tunnel Support. Rock Mech. 1974, 6, 189–236. [Google Scholar] [CrossRef] [Scilit]
  6. Alejano, L.R. Rock Mass Classification Systems: A Useful Rock Mechanics Tool, Often Misused. Rock Mech. Rock Eng. 2025, 58, 11147–11167. [Google Scholar] [CrossRef] [Scilit]
  7. Buyer, A.; Aichinger, S.; Schubert, W. Applying Photogrammetry and Semi-Automated Joint Mapping for Rock Mass Characterization. Eng. Geol. 2020, 264, 105332. [Google Scholar] [CrossRef] [Scilit]
  8. Liu, Q.; Tian, Y.; Liu, D.; Jiang, Y. Updates to JRC-JCS Model for Estimating the Peak Shear Strength of Rock Joints Based on Quantified Surface Description. Eng. Geol. 2017, 228, 282–300. [Google Scholar] [CrossRef] [Scilit]
  9. Morad, D.; Sagy, A.; Tal, Y.; Hatzor, Y.H. Fault Roughness Controls Sliding Instability. Earth Planet. Sci. Lett. 2022, 579, 117365. [Google Scholar] [CrossRef] [Scilit]
  10. Han, G.; Jing, H.; Jiang, Y.; Liu, R.; Wu, J. Effect of Cyclic Loading on the Shear Behaviours of Both Unfilled and Infilled Rough Rock Joints under Constant Normal Stiffness Conditions. Rock Mech. Rock Eng. 2020, 53, 31–57. [Google Scholar] [CrossRef] [Scilit]
  11. Zhao, Y.; Zhang, C.; Wang, Y.; Lin, H. Shear-Related Roughness Classification and Strength Model of Natural Rock Joint Based on Fuzzy Comprehensive Evaluation. Int. J. Rock Mech. Min. Sci. 2021, 137, 104550. [Google Scholar] [CrossRef] [Scilit]
  12. Ríos-Bayona, F.; Johansson, F.; Larsson, J.; Mas-Ivars, D. Peak Shear Strength of Natural, Unfilled Rock Joints in the Field Based on Data from Drill Cores—A Conceptual Study Based on Large Laboratory Shear Tests. Rock Mech. Rock Eng. 2022, 55, 5083–5106. [Google Scholar] [CrossRef] [Scilit]
  13. Pirzada, M.A.; Bahaaddini, M.; Andersen, M.S.; Roshan, H. Coupled Hydro-Mechanical Behaviour of Rock Joints during Normal and Shear Loading. Rock Mech. Rock Eng. 2023, 56, 1219–1237. [Google Scholar] [CrossRef] [Scilit]
  14. Ryder, J.A. Excess Shear Stress in the Assessment of Geologically Hazardous Situations. J. South Afr. Inst. Min. Metall. 1988, 88, 27–39. [Google Scholar]
  15. Feng, G.L.; Feng, X.T.; Chen, B.R.; Xiao, Y.X.; Zhao, Z.N. Effects of Structural Planes on the Microseismicity Associated with Rockburst Development Processes in Deep Tunnels of the Jinping-II Hydropower Station, China. Tunn. Undergr. Space Technol. 2019, 84, 273–280. [Google Scholar] [CrossRef] [Scilit]
  16. Battulwar, R.; Zare-Naghadehi, M.; Emami, E.; Sattarvand, J. A State-of-the-Art Review of Automated Extraction of Rock Mass Discontinuity Characteristics Using Three-Dimensional Surface Models. J. Rock Mech. Geotech. Eng. 2021, 13, 920–936. [Google Scholar] [CrossRef] [Scilit]
  17. Barton, N.; Wang, C.; Yong, R. Advances in Joint Roughness Coefficient (JRC) and Its Engineering Applications. J. Rock Mech. Geotech. Eng. 2023, 15, 3352–3379. [Google Scholar] [CrossRef] [Scilit]
  18. Ríos-Bayona, F.; Johansson, F.; Mas-Ivars, D. Prediction of Peak Shear Strength of Natural, Unfilled Rock Joints Accounting for Matedness Based on Measured Aperture. Rock Mech. Rock Eng. 2021, 54, 1533–1550. [Google Scholar] [CrossRef] [Scilit]
  19. Zhou, C.B.; Chen, Y.F.; Hu, R.; Yang, Z. Groundwater Flow through Fractured Rocks and Seepage Control in Geotechnical Engineering: Theories and Practices. J. Rock Mech. Geotech. Eng. 2023, 15, 1–36. [Google Scholar] [CrossRef] [Scilit]
  20. Tsang, C.F. Coupled Thermo-Hydro-Mechanical Processes in Fractured Rocks: Some Past Scientific Highlights and Future Research Directions. Rock Mech. Rock Eng. 2024, 57, 5303–5316. [Google Scholar] [CrossRef] [Scilit]
  21. Wu, Z.R.; Zheng, Y.L.; Deng, B.Z.; Deng, S.X. Influence of Intermediate Principal Stress on Rock Strength: Insights from Closed Crack Evolution under True Triaxial Compression. Theor. Appl. Fract. Mech. 2025, 136, 104786. [Google Scholar] [CrossRef] [Scilit]
  22. Wu, Z.R.; Wang, J.; Deng, S.X.; Wang, Z.; Zhou, Y.B.; Deng, B.Z. Experimental Study on the Evolution of 3D Surface Flaws under True Triaxial Stress State. Case Stud. Constr. Mater. 2025, 22, e04827. [Google Scholar] [CrossRef] [Scilit]
  23. Song, L.; Bai, Z.; Jiang, Q.; Zhu, B.; Wang, G.; Gu, Y. Advancing the Understanding of Infilled Joint Shear Behavior: A Review of Modeling, Measurement, and Influential Factors. Rock Mech. Rock Eng. 2025, 58, 9265–9295. [Google Scholar] [CrossRef] [Scilit]
  24. Indraratna, B.; Premadasa, W.; Brown, E.T.; Gens, A.; Heitor, A. Shear Strength of Rock Joints Influenced by Compacted Infill. Int. J. Rock Mech. Min. Sci. 2014, 70, 296–307. [Google Scholar] [CrossRef] [Scilit]
  25. Meng, F.Z.; Zhou, H.; Wang, Z.Q.; Zhang, L.M.; Kong, L.; Li, S.J.; Zhang, C.Q. Influences of Shear History and Infilling on the Mechanical Characteristics and Acoustic Emissions of Joints. Rock Mech. Rock Eng. 2017, 50, 2039–2057. [Google Scholar] [CrossRef] [Scilit]
  26. Wang, G.; Wu, X.L.; Zhang, X.D.; Zhang, Z.S.; Zhao, Z.P.; Han, W.; Wang, Y.; Zhao, C. Macro–Microscopic Study on the Shear Characteristics of Filled Joints with Different Roughnesses. Arab. J. Sci. Eng. 2020, 45, 8331–8348. [Google Scholar] [CrossRef] [Scilit]
  27. Zhao, Y.; Zhang, L.; Wang, W.; Liu, Q.; Tang, L.; Cheng, G. Experimental Study on Shear Behavior and a Revised Shear Strength Model for Infilled Rock Joints. Int. J. Geomech. 2020, 20, 04020141. [Google Scholar] [CrossRef] [Scilit]
  28. Zhuang, X.Y.; Chun, J.W.; Zhu, H.H. A Comparative Study on Unfilled and Filled Crack Propagation for Rock-Like Brittle Material. Theor. Appl. Fract. Mech. 2014, 72, 110–120. [Google Scholar] [CrossRef] [Scilit]
  29. Cao, Y.; Zhang, Y.; Liu, Z.; Bao, M. An Experimental Study of the Effects of Filling Degree on Shear Behavior and Acoustic Emission Characteristics of Kaolinite-Filled Granite Joints. KSCE J. Civ. Eng. 2024, 28, 2966–2981. [Google Scholar] [CrossRef] [Scilit]
  30. Huang, X.; Qi, S.; Xia, K.; Shi, X. Particle Crushing of a Filled Fracture during Compression and Its Effect on Stress Wave Propagation. J. Geophys. Res. Solid Earth 2018, 123, 5559–5587. [Google Scholar] [CrossRef] [Scilit]
  31. Shu, P.Y.; Li, H.H.; Wang, T.T.; Ueng, T.H. Dynamic Strength of Rock with Single Planar Joint under Various Loading Rates at Various Angles of Loads Applied. J. Rock Mech. Geotech. Eng. 2018, 10, 545–554. [Google Scholar] [CrossRef] [Scilit]
  32. Zhou, T.; Han, Z.Y.; Li, D.Y.; Chen, J.R. Experimental Study of the Mechanical and Fracture Behavior of Flawed Sandstone Subjected to Coupled Static-Repetitive Impact Loading. Theor. Appl. Fract. Mech. 2022, 117, 103161. [Google Scholar] [CrossRef] [Scilit]
  33. Wang, F.L.; Wang, S.H.; Yao, W.; Li, X.; Meng, F.Z.; Xia, K.W. Effect of Roughness on the Shear Behavior of Rock Joints Subjected to Impact Loading. J. Rock Mech. Geotech. Eng. 2023, 15, 339–349. [Google Scholar] [CrossRef] [Scilit]
  34. Melosh, H.J. Dynamical Weakening of Faults by Acoustic Fluidization. Nature 1996, 379, 601–606. [Google Scholar] [CrossRef] [Scilit]
  35. Xie, S.; Li, J.; Wang, S.; Li, X. Experimental Study on Dynamic Shear Properties of Infilled Joints under Dynamic Shearing: Insights from Normal Stress and Shear Rate. Rock Mech. Rock Eng. 2026, 1–18. [Google Scholar] [CrossRef] [Scilit]
  36. Yang, J.N.; Fan, P.X.; Wang, J.H.; Xing, H.Z.; Wang, M.Y.; Qian, Q.H. Energy Characteristics during the Progressive Shear Failure of Rock Joints and Brittleness Evaluation. Int. J. Min. Sci. Technol. 2026, 36, 829–847. [Google Scholar] [CrossRef] [Scilit]
  37. Lang, Y.X.; Liang, Z.Z.; Qian, X.K.; Dong, Z.; Wu, N. A Study on the Effect of Rock Discontinuities on Stress Wave Propagation and Dynamic Fracture. Chin. J. Undergr. Space Eng. 2023, 19, 1896–1906. [Google Scholar]
  38. Li, Y.X.; Liu, J.F.; Qin, L. Experimental Study on Rule of Energy Dissipation of Stress Wave across Rock Joint. J. Exp. Mech. 2011, 26, 85–90. [Google Scholar]
  39. Wang, F.L.; Xia, K.W.; Yao, W.; Wang, S.H.; Wang, C.L.; Xiu, Z.G. Slip Behavior of Rough Rock Discontinuity under High Velocity Impact: Experiments and Models. Int. J. Rock Mech. Min. Sci. 2021, 144, 104831. [Google Scholar] [CrossRef] [Scilit]
  40. Wang, F.L.; Wu, B.B.; Wang, S.H.; Meng, F.Z.; Xiu, Z.G.; Wang, C.L. Shear Response of Rough Rock Discontinuities Subjected to Impact Loading: Experimental Study and Theoretical Modelling. Lithosphere 2022, 2022, 1192067. [Google Scholar] [CrossRef] [Scilit]
  41. Deng, S.X.; Wang, M.Y.; Li, J.; Zhang, G.K.; Wang, Z. Mechanism and Simulation Experiment of Slip-Type Rock Bursts Triggered by Impact Disturbances. Chin. J. Geotech. Eng. 2020, 42, 2215–2221. [Google Scholar]
  42. Li, L.P.; Ju, X.Y.; Pan, Y.S.; Wang, L.; Tai, Y.L. Experimental Study of Anomalously Low Friction Effect of Block Rock Mass Subjected to Weak Confining Pressure and Strong Vertical Impact Disturbance. J. Exp. Mech. 2019, 34, 1068–1076. [Google Scholar]
  43. Liu, T.T.; Li, J.C.; Li, H.B.; Li, X.P.; Zheng, Y.; Liu, H. Experimental Study of S-Wave Propagation through a Filled Rock Joint. Rock Mech. Rock Eng. 2017, 50, 2645–2657. [Google Scholar] [CrossRef] [Scilit]
  44. Wang, S.; Wang, Z.; Wang, J.; Zhou, R. Determination of Constitutive Parameters of Filled Joints under Repeated Impact Loads Using Indirect Inversion Method. Environ. Earth Sci. 2026, 85, 312. [Google Scholar] [CrossRef] [Scilit]
  45. Binaree, T.; Azéma, E.; Estrada, N.; Renouf, M.; Preechawuttipong, I. Combined Effects of Contact Friction and Particle Shape on Strength Properties and Microstructure of Sheared Granular Media. Phys. Rev. E 2020, 102, 022901. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  46. Wang, G.; Liu, Y.; Xu, J. Stress Localization in Brittle Rock-Like Samples of Particle-Filled Joints under Direct Shear Loading. KSCE J. Civ. Eng. 2021, 25, 345–355. [Google Scholar] [CrossRef] [Scilit]
Applsci 16 08733 g001
Figure 1. Custom-developed impact-disturbance testing apparatus for blocky rock masses.
Figure 1. Custom-developed impact-disturbance testing apparatus for blocky rock masses.
Applsci 16 08733 g001
Applsci 16 08733 g002
Figure 2. Schematic layout of the blocky-rock model.
Figure 2. Schematic layout of the blocky-rock model.
Applsci 16 08733 g002
Applsci 16 08733 g003
Figure 3. B2 rock block with quartz sand distributed over the contact surface.
Figure 3. B2 rock block with quartz sand distributed over the contact surface.
Applsci 16 08733 g003
Applsci 16 08733 g004
Figure 4. Horizontal-displacement time histories of block B2 under impact disturbance at different axial load levels and quartz-sand particle-size conditions. (a) 6–8 mesh quartz-sand infill. (b) 8–16 mesh quartz-sand infill. (c) 16–26 mesh quartz-sand infill. (d) 40–70 mesh quartz-sand infill.
Figure 4. Horizontal-displacement time histories of block B2 under impact disturbance at different axial load levels and quartz-sand particle-size conditions. (a) 6–8 mesh quartz-sand infill. (b) 8–16 mesh quartz-sand infill. (c) 16–26 mesh quartz-sand infill. (d) 40–70 mesh quartz-sand infill.
Applsci 16 08733 g004
Applsci 16 08733 g005
Figure 5. Relationship between axial load and final residual block-slip displacement.
Figure 5. Relationship between axial load and final residual block-slip displacement.
Applsci 16 08733 g005
Applsci 16 08733 g006
Figure 6. Time histories of block-slip displacement under different axial load and quartz-sand particle-size conditions. (a) Axial load: 100 N. (b) Axial load 200 N. (c) Axial load: 300 N.
Figure 6. Time histories of block-slip displacement under different axial load and quartz-sand particle-size conditions. (a) Axial load: 100 N. (b) Axial load 200 N. (c) Axial load: 300 N.
Applsci 16 08733 g006
Applsci 16 08733 g007
Figure 7. Relationship between characteristic quartz-sand particle size and final residual block-slip displacement.
Figure 7. Relationship between characteristic quartz-sand particle size and final residual block-slip displacement.
Applsci 16 08733 g007
Applsci 16 08733 g008
Figure 8. Schematic illustration of dynamic unloading and slip triggering. (a) Initial stable load-bearing state. (b) Transient interfacial unloading. (c) Rapid block slip. (d) Interfacial reclosure and formation of residual displacement.
Figure 8. Schematic illustration of dynamic unloading and slip triggering. (a) Initial stable load-bearing state. (b) Transient interfacial unloading. (c) Rapid block slip. (d) Interfacial reclosure and formation of residual displacement.
Applsci 16 08733 g008
Applsci 16 08733 g009
Figure 9. Schematic illustration of the transition from particle rolling to wedging. (a) Rolling and rearrangement of coarse particles. (b) Wedging and constraint of fine particles.
Figure 9. Schematic illustration of the transition from particle rolling to wedging. (a) Rolling and rearrangement of coarse particles. (b) Wedging and constraint of fine particles.
Applsci 16 08733 g009
Table 1. Test matrix.
Table 1. Test matrix.
Axial Load (N)100150200250300350400
Particle Size
Class (Mesh)
6–8T1-1T1-2T1-3T1-4T1-5T1-6T1-7
8–16T2-1T2-2T2-3T2-4T2-5T2-6T2-7
16–26T3-1T3-2T3-3T3-4T3-5T3-6T3-7
40–70T4-1T4-2T4-3T4-4T4-5T4-6T4-7
Table 2. Final residual block-slip displacement under different axial load and quartz-sand particle-size conditions.
Table 2. Final residual block-slip displacement under different axial load and quartz-sand particle-size conditions.
Axial Load (N)6–8 Mesh (mm)8–16 Mesh (mm)16–26 Mesh (mm)40–70 Mesh (mm)
1001.1890.9920.8100.729
1500.8760.6280.5690.566
2000.6720.5580.4500.300
2500.3810.3230.3200.270
3000.2660.2310.2300.193
3500.1750.2120.1600.109
4000.1210.0980.0980.091
Reduction from 100 to 400 N (%)89.8290.1287.9087.52
Table 3. Characteristic parameters of impact-induced block slip under different axial load and quartz-sand particle-size conditions.
Table 3. Characteristic parameters of impact-induced block slip under different axial load and quartz-sand particle-size conditions.
Quartz-Sand Particle Size (Mesh)Slip Onset Time (ms)Maximum Slip Velocity (mm/ms)Slip-Stage Duration (ms)
6–825.520–30.1280.0035–0.042349.506–97.989
8–1627.274–31.8830.0041–0.027545.484–62.303
16–2626.399–39.1960.0042–0.025645.192–89.068
40–7027.701–42.1050.0037–0.019458.225–84.807
Table 4. Fitted parameters of the exponential relationship between axial load and residual slip displacement.
Table 4. Fitted parameters of the exponential relationship between axial load and residual slip displacement.
Quartz-Sand Particle Size (Mesh) a (mm) b (N−1)R2
6–82.50520.0071940.9891
8–161.93990.0068890.9797
16–261.52730.0063640.9962
40–701.52040.0071840.9794
Table 5. Fitted parameters for the linear relationship between characteristic quartz-sand particle size and residual slip displacement.
Table 5. Fitted parameters for the linear relationship between characteristic quartz-sand particle size and residual slip displacement.
Axial Load (N) α β (mm) R2
1000.18690.66730.9966
2000.14120.29660.9489
3000.02560.19400.8810
Table 6. Difference in residual slip displacement between coarse- and fine-grained infill conditions at representative axial load levels.
Table 6. Difference in residual slip displacement between coarse- and fine-grained infill conditions at representative axial load levels.
Axial Load (N)Residual Slip Displacement for 6–8 Mesh Infill (mm)Residual Slip Displacement for 40–70 Mesh Infill (mm)Difference (mm)
1001.1890.7290.460
2000.6720.3000.372
3000.2660.1930.073
4000.1210.0910.030
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Wei, C.; Song, Z.; Deng, S.; Liu, C.; Wu, Z. Dynamic Sliding Behavior of Sand-Filled Rock Joints Under Impact Loading: Evolution of Particle-Size Effects. Appl. Sci. 2026, 16, 8733. https://doi.org/10.3390/app16178733

AMA Style

Wei C, Song Z, Deng S, Liu C, Wu Z. Dynamic Sliding Behavior of Sand-Filled Rock Joints Under Impact Loading: Evolution of Particle-Size Effects. Applied Sciences. 2026; 16(17):8733. https://doi.org/10.3390/app16178733

Chicago/Turabian Style

Wei, Chao, Zhu Song, Shuxin Deng, Chenkang Liu, and Zhuorui Wu. 2026. "Dynamic Sliding Behavior of Sand-Filled Rock Joints Under Impact Loading: Evolution of Particle-Size Effects" Applied Sciences 16, no. 17: 8733. https://doi.org/10.3390/app16178733

APA Style

Wei, C., Song, Z., Deng, S., Liu, C., & Wu, Z. (2026). Dynamic Sliding Behavior of Sand-Filled Rock Joints Under Impact Loading: Evolution of Particle-Size Effects. Applied Sciences, 16(17), 8733. https://doi.org/10.3390/app16178733

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop