Search Results (10)

With the rapid development of marine engineering, large−diameter steel pipe piles are increasingly used in infrastructure construction, such as bridges, docks, and offshore wind power projects. Therefore, studying the shear behavior of the sand–steel interface is of great importance. In this study, the traditional vane shear apparatus was improved by utilizing its torsional shear actuator, adding an overlying pressure fixing device, and applying lateral pressure through a compressive spring. The original cross plate was replaced with a cylindrical steel rod to simulate the shear behavior of the large−diameter pile–sand interface under different stress states. Experimental results show that this apparatus effectively solves the problem of soil loss due to the shear gap in both the ring shear and direct shear tests under smooth interface conditions. As the shear rate (2°/min, 4°/min, 6°/min) increased, the peak and residual shear stresses decreased, while the shear stress increased with vertical confinement pressure, accompanied by significant residual stress. As the relative density of sand increased from 27.4% to 72.2%, the shear behavior transitioned from contraction to dilation. Regarding surface roughness, the experiment identified a critical threshold: when roughness is below this threshold, it significantly affects the peak shear strength; when above this threshold, the effect is smaller, and failure shifts to the internal sand body. This study provides valuable insights into the mechanics of the sand–steel interface and contributes to optimizing the foundation design for marine infrastructure. Full article

During the excavation process of a Tunnel Boring Machine (TBM), the cutterhead exerts significant torque on the tunnel structure, which potentially causes torsional shear deformation at segment ring joints. Thus, examining the characteristics of torsional shear deformation and the shear-bearing performance of segment joints under construction torque is crucial for the design and safety of segment structures and the construction of TBM tunnels. To achieve this, a refined finite element model of the segment joints was developed to study their torsional shear resistance under varying axial forces and with or without mortise and tenon. Furthermore, the failure modes of bolts and the damage characteristics of segment concrete during torsional shear deformation are analyzed. The results show that the load-bearing process of torsional shear deformation in segment joints consists of three stages: development of the friction at the segment interface (Stage I), development of the bolt force (Stage II), and development of the mortise and tenon force (Stage III). It is noteworthy that axial force is the primary factor in enhancing the torsional shear resistance of the segmental joints. Moreover, as the torsional shear deformation increases, the contact and compression occur between the bolts and the segment bolt holes as well as between the mortise and tenon, leading to the yielding of the bolts and the failure of the concrete at the joints. Consequently, the segment concrete around the mortise and tenon and the bolt hole is prone to cracking and crushing. To prevent shear failure of the bolts, it is recommended that the rotational angle of segment be maintained at less than 0.045°. Full article

A standardized method to evaluate the material properties of surimi gels has to be updated because of the lack of accuracy and the repeatability of data obtained from conventional ways. To investigate the relationships between the different texture measurement methods used in surimi gels, 250 batches of different surimi gels were used. The textural properties of surimi gels made with or without whey protein concentrate (SG-WP), potato starch (SG-PS), or dried egg white (SG-EW) were measured under torsion, tensile, and penetration tests. The correlation between the textural properties related to the deformation and hardness of surimi gels without any added ingredients (SG) was linear (R² > 0.85). However, the R² values of the shear strain and tensile strain of SG-WP and SG-EW were significantly lower than that of SG. The strain distributions of surimi gels with and without added ingredients were estimated by digital image correlation (DIC) analysis. The results showed that the local strain concentration in SG-WP and SG-EW was significantly higher than that of SG in the failure ring tensile test and the torsion test (p < 0.05). DIC analysis was an effective tool for evaluating the strain distribution characteristics of surimi gels upon fracture from torsion, penetration, and tension. Full article

Slope failures in roadway embankments are common occurrences and can lead to traffic disruptions and large costs to repair damage. In areas with high-plasticity clays, special attention must be paid to characterizing both the stratigraphy and the potential for strength loss. This study demonstrates the use of an integrated site characterization approach, which seeks to utilize results from geotechnical and geophysical tests to understand the behavior of a landslide in west Alabama. The timing and mechanism of the initial failure causing the preexisting shear plane at this site are not known. Results from electrical resistivity and seismic geophysical tests are integrated with information from borings and index tests to develop a representative cross-section for the landslide, and torsional ring shear results are used to measure the drained fully softened and residual strengths. Both the limit equilibrium (LEM) and strength reduction method (SRM) analyses are used to examine possible failure mechanisms. The results show good agreement between noncircular LEM and SRM analyses and indicate that the initial failure was likely due to undrained loading of the clay. Analyses utilizing the residual drained strength envelopes produce FS values significantly lower than 1 indicating the slope to be unstable when soil on the failure plane exists at the residual state. Sensitivity analyses suggest that the combined effect of lowering the water table and strength recovery may explain the intermittent nature of movements. Full article

The main objective of the study is to estimate the shear resistance mobilized on the slope surface under large deformation and to identify the failure mechanism of the landslide through the simulation model. The field investigations were carried out using Geophysical tests, and the laboratory tests were conducted to identify the engineering properties of the soil with weathering characteristics of the parent rock. The residual shear strength parameters from Torsional ring shear tests were used in LS-RAPID numerical simulation software to study the mechanism of the landslide. The critical pore water pressure ratio (r_u = 0.32) required for the initiation of a landslide was obtained. The increase in pore water pressure reduces the soil matric suction and thereby results in the reduction of the shear strength of the soil. The progressive failure mechanism and the three landslide processes (initiation, run out and deposition) are investigated. The velocity of the moving landslide mass in the role of demolishing the building is studied and helps in finding suitable remedial measures for the nearby building. The empirical rainfall threshold based on the antecedent rainfall was developed and revealed that either a high daily rainfall intensity of 142 mm without any antecedent rainfall, or an antecedent rainfall of 151 mm for a cumulative period of 5 days with even continuous normal rainfall can initiate landslide. Full article

Slope failures in high plasticity clay deposits are common occurrences in many parts of the world. In western and central Alabama, expansive Prairie clays are commonly found, and shallow slope failures have occurred in both fill and cut slopes containing these high plasticity clays. The objective of this study was to examine the effects of suction and the use of nonlinear strength envelopes on the embankment stability of a section of highway AL-5. The testing program consisted of fifteen ring shear tests performed using a Bromhead Ring Shear Device. The results of the tests were used to develop both linear and nonlinear fully softened and residual strength envelopes. The saturated strength envelopes are then used in a limit equilibrium slope stability analysis with and without the effects of suction. The results show stability (factor of safety >1) for all cases except the residual friction angle without suction. Given these results, large slope failures are unlikely to occur in this area, but surficial failures and deformations due to creep may be possible. These results demonstrate the importance of considering the effects of suction and nonlinear strength envelopes when examining the potential for shallow slope failures in high plasticity clays. Full article

Mechanical face seals are crucial components of automotive cooling water pumps and affect the safe operation of the pump. This article focuses on the effect of friction instabilities on the wear of the seals. Friction instabilities, such as stick-slip, occur when the axle is decelerated or operated at a low speed. Based on previous studies, a simulation model is proposed of a mechanical face seal that considers the interaction of asperities of non-Gaussian surfaces and the heat transfer between the sealing rings. According to the Archard wear equation, a numerical wear simulation is performed, and the wear distance rate and wear time rate are obtained. A comparison of the contact pressure of the Gaussian and non-Gaussian surfaces indicates that the latter is more likely to generate high contact pressure, thereby producing more significant wear. The viscous shear heat and frictional heat due to asperity contact decrease with an increase in the thickness of the tapered film. As the shaft decelerates, the wear distance rate increases with an increase in the axial stiffness. The axial damping only affects the duration of the oscillations. The wear time rate decreases with an increase in the torsional stiffness and torsional damping. The results of this research provide guidelines for estimating the wear of mechanical seals when friction instabilities occur. Full article

Atrazine (ATZ) is one of the most heavily used types of herbicide that is currently applied in the agricultural industry all around the world, especially Australia and the United States. This study investigates the effect of atrazine contamination on the mechanical characteristics of two Western Australian natural clays and one commercial type of clay. A series of the Atterberg limit, compaction, and torsional ring shear tests were performed on the clays contaminated with 2, 4, and 6% atrazine content. The results showed that increasing the atrazine content led to a reduction in both liquid limit (LL) and plastic (PL) of the tested soils. Similarly, the optimum moisture content (OMC) and maximum dry density (MDD) decreased by increasing the atrazine in all tested clays. The ring shear results showed that the peak shear strength and residual stress ratio of the clays decreased by increasing the contamination. Also, the results showed that atrazine contamination caused an increase in cohesion and a decrease in the friction angle of the tested soils. Also, longer periods of contamination caused a reduction in strength characteristics of the tested soils. Full article

The clinical ultrasound community demands mechanisms to obtain the viscoelastic biomarkers of soft tissue in order to quantify the tissue condition and to be able to track its consistency. Torsional Wave Elastography (TWE) is an emerging technique proposed for interrogating soft tissue mechanical viscoelastic constants. Torsional waves are a particular configuration of shear waves, which propagate asymmetrically in-depth and are radially transmitted by a disc and received by a ring. This configuration is shown to be particularly efficient in minimizing spurious p-waves components and is sensitive to mechanical constants, especially in cylinder-shaped organs. The objective of this work was to validate (TWE) technique against Shear Wave Elasticity Imaging (SWEI) technique through the determination of shear wave velocity, shear moduli, and viscosity of ex vivo chicken liver samples and tissue mimicking hydrogel phantoms. The results of shear moduli for ex vivo liver tissue vary 1.69–4.0kPa using TWE technique and 1.32–4.48kPa using SWEI technique for a range of frequencies from 200 to 800Hz. Kelvin–Voigt viscoelastic parameters reported values of $\mu$ = 1.51kPa and $\eta$ = 0.54Pa·s using TWE and $\mu$ = 1.02kPa and $\eta$ = 0.63Pa·s using SWEI. Preliminary results show that the proposed technique successfully allows reconstructing shear wave velocity, shear moduli, and viscosity mechanical biomarkers from the propagated torsional wave, establishing a proof of principle and warranting further studies. Full article

A novel torsional wave sensor designed to characterize mechanical properties of soft tissues is presented in this work. Elastography is a widely used technique since the 1990s to map tissue stiffness. Moreover, quantitative elastography uses the velocity of shear waves to achieve the shear stiffness. This technique exhibits significant limitations caused by the difficulty of the separation between longitudinal and shear waves and the pressure applied while measuring. To overcome these drawbacks, the proposed torsional wave sensor can isolate a pure shear wave, avoiding the possibility of multiple wave interference. It comprises a rotational actuator disk and a piezoceramic receiver ring circumferentially aligned. Both allow the transmission of shear waves that interact with the tissue before being received. Experimental tests are performed using tissue mimicking phantoms and cervical tissues. One contribution is a sensor sensitivity study that has been conducted to evaluate the robustness of the new proposed torsional wave elastography (TWE) technique. The variables object of the study are both the applied pressure and the angle of incidence sensor–phantom. The other contribution consists of a cervical tissue characterization. To this end, three rheological models have fit the experimental data and a static independent testing method has been performed. The proposed methodology permits the reconstruction of the mechanical constants from the propagated shear wave, providing a proof of principle and warranting further studies to confirm the validity of the results. Full article