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Mechanical Properties and Engineering Applications of Special Soils
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Mechanical Properties and Engineering Applications of Special Soils

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Civil Engineering".

Deadline for manuscript submissions: 20 July 2024 | Viewed by 25805

Special Issue Editors

Prof. Dr. Xianwei Zhang

E-Mail Website
Guest Editor
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
Interests: geotechnical engineering; soil mechanics; special soil
Special Issues, Collections and Topics in MDPI journals
Dr. Xinyu Liu

E-Mail Website
Guest Editor
School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: residual soil; weathered rock; structured clay; mudstone
Special Issues, Collections and Topics in MDPI journals
Dr. Ran An

E-Mail Website
Guest Editor
School of Civil Engineering, Hefei University of Technology, Hefei 230009, China
Interests: soil mechanics; in situ tests; soil microstructure
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We are inviting submissions to this Special Issue on “Mechanical Properties and Engineering Applications of Special Soils”.

Geotechnical design and construction all over the world are constantly challenged by a variety of special soils, including residual soil, loess, frozen soil, expansive soil, glacial till, and contaminated soil. The mechanical properties of special soils are significantly different from those of common sedimentary clays and sands, which poses great difficulties for engineering applications. The detailed characterizations of these special soils are of great importance if the related engineering is to be conducted in a secure and economical way. This Special Issue serves as an opportunity for researchers to present their high-quality works toward mechanical properties and engineering applications of special soils.

Sample topics of interest of this Special Issue include but are not limited to mechanics, theory, in situ and laboratory tests, and numerical analysis of special soils. Special soil engineering cases such as foundation excavation, ground improvement, slope, tunnel, and geohazard are also welcomed.

Prof. Dr. Xianwei Zhang
Dr. Xinyu Liu
Dr. Ran An
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • special soil
  • mechanical properties
  • engineering application
  • geohazard

Published Papers (20 papers)

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13 pages, 3946 KiB  
Article
Mechanical Characteristics and Damage Constitutive Model of Fiber-Reinforced Cement-Stabilized Soft Clay
by Tiecheng Yan, Xingyuan Zhang, Sutong Cai, Zefeng Zhou, Ran An and Xianwei Zhang
Appl. Sci. 2024, 14(4), 1378; https://doi.org/10.3390/app14041378 - 08 Feb 2024
Viewed by 464
Abstract
Marine soft clays are prevalent in coastal regions of China, giving rise to engineering challenges such as salt swelling, corrosion, and load bearing in foundations with soft soil. This study is dedicated to enhancing the mechanical properties of fiber-reinforced cement-stabilized soft clay (FCSSC) [...] Read more.
Marine soft clays are prevalent in coastal regions of China, giving rise to engineering challenges such as salt swelling, corrosion, and load bearing in foundations with soft soil. This study is dedicated to enhancing the mechanical properties of fiber-reinforced cement-stabilized soft clay (FCSSC) and revealing its strengthening mechanism. Uniaxial compression tests are performed to explore the impact of fiber length, fiber amount, and curing ages on mechanical behavior. The stabilization mechanisms of cement and glass fibers are explored through damage analyses and microscopy. Based on the experimental results, a damage constitutive model is formulated for FCSSC, and its validity is established by comparing fitting curves with testing curves. The results demonstrate a significant improvement in the mechanical properties of the stabilized soil, attributed to the synergistic effects of the cement and glass fibers. The growth rate of the unconfined compressive strength decreased with increasing curing ages. Notably, the fiber length significantly impacted the strength index, with short-chopped fibers playing a crucial role in strength enhancement. The compressive strength exhibited an initial increase followed by a decrease with rising fiber content, reaching a maximum between 0.3% and 0.4%. The bridging effect of the glass fibers proved effective in inhibiting compression crack expansion and mitigating structural damage of the soil sample. However, excessive fiber content or length led to improved local porosity, resulting in the deterioration of strength and deformation properties. The stress–strain curves fitted using the proposed damage constitutive model accurately reflected the stress–strain relationship and deformation characteristics of the FCSSC. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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14 pages, 1564 KiB  
Article
Predicting Swell in Clay-Sand Mixtures Used in Liners
by Muawia Dafalla
Appl. Sci. 2023, 13(20), 11161; https://doi.org/10.3390/app132011161 - 11 Oct 2023
Viewed by 600
Abstract
A method to predict the swellability of clay-sand mixtures is proposed. This model is a modified form of the Studds (1997) prediction model for clay-sand mixtures. The new proposed model uses the laboratory fall cone penetration technique to produce a characterization chart. This [...] Read more.
A method to predict the swellability of clay-sand mixtures is proposed. This model is a modified form of the Studds (1997) prediction model for clay-sand mixtures. The new proposed model uses the laboratory fall cone penetration technique to produce a characterization chart. This chart presents slope levels that can be used to obtain an equation for the final clay void ratio versus the vertical effective stress for clays. The porosity of the clay-sand mixtures was worked out based on a correction factor obtained from compression and porosity measurements in the laboratory. The porosity of the mixture was merged into the clay profile equation to compute the final clay void ratio at a specified stress level, which made it possible to predict the swelling behavior for different and variable stress levels. The swellability slope was obtained using fall cone tests conducted on the fine portion. Mixtures of kaolinite and bentonite were introduced to represent soils with different swell potentials. The fall cone measurements of a few points can be used to establish the swellability relationships for natural clay. Merging fall cone points with the swellability slope chart can define the profile of the vertical effective stress versus the clay void ratio. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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12 pages, 2648 KiB  
Article
Determining the Macrostructural Stability of Compacted Wyoming Bentonites by a Disaggregation Method
by José Manuel Moreno-Maroto, Óscar Merlo, Joel Torres-Serra, Jacinto Alonso-Azcárate, Mark Tyrer and Vicente Navarro
Appl. Sci. 2023, 13(20), 11159; https://doi.org/10.3390/app132011159 - 11 Oct 2023
Viewed by 649
Abstract
The use of compacted bentonites in radioactive waste repository barriers is a relevant application of geoenvironmental engineering. The on-site structural characteristics of the bentonites determine the performance and integrity of the barrier. The present work addresses the adaptation of the standardized sand equivalent [...] Read more.
The use of compacted bentonites in radioactive waste repository barriers is a relevant application of geoenvironmental engineering. The on-site structural characteristics of the bentonites determine the performance and integrity of the barrier. The present work addresses the adaptation of the standardized sand equivalent shaking method for the controlled disaggregation of Wyoming bentonite specimens prepared at low, medium, and high compaction. The evolution of the macrostructural units’ size distribution was determined by sieving at different shaking times. The stability of the compacted material increases with dry density. However, if enough energy is applied in the disaggregation process, the size distribution of the macrostructural units after disaggregation has the same characteristics as that of the uncompacted starting material, regardless of the applied degree of compaction. Since the disaggregation rate is a function of the aggregation level (compaction), it follows that compaction energy is not only spent on reducing porosity but also on generating more stable macrostructural units. These findings pave the way for future research with different materials and test conditions (compaction, moisture, etc.). In addition, the proposed shaking method is adaptable and could also be used in other sectors, such as agriculture, to determine the structural stability of natural soils. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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16 pages, 2969 KiB  
Article
Research on the Accumulated Plastic Strain of Expansive Soil under Subway Loading
by Lei Zhu, Ying Guo, Gan Cheng and Xiangyang Liu
Appl. Sci. 2023, 13(18), 9994; https://doi.org/10.3390/app13189994 - 05 Sep 2023
Viewed by 821
Abstract
Expansive soil near Hefei Xinqiao International Airport was selected as the research focus. The effects of different loading modes on the dynamic strain of the saturated remodeled expansive soil was investigated by indoor dynamic triaxial tests and the effect of three factors, intermittent [...] Read more.
Expansive soil near Hefei Xinqiao International Airport was selected as the research focus. The effects of different loading modes on the dynamic strain of the saturated remodeled expansive soil was investigated by indoor dynamic triaxial tests and the effect of three factors, intermittent loading ratio, static deviatoric stress, and cyclic stress ratio, on the accumulated plastic strain of saturated remodeled expansive soil under intermittent subway cyclic loading was analyzed. Finally, the corresponding accumulated plastic strain calculation model was established based on the test results. The research results show that the loading modes do not affect the overall development mode of the strain and, under intermittent loading, the strain tends to be more stable. Under intermittent loading, when the number of cycles is the same, the larger the intermittent loading ratio, the smaller the accumulated plastic strain. The effect of static deviatoric stress and cyclic stress ratio on strain accumulation is significant. Based on the hyperbolic model, an accumulated plastic strain calculation model related to the number of cycles of remolded expansive soil under the load of the Hefei subway was proposed, which has a certain reference significance for the design, safety assessment, and safe operation of the Hefei subway. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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29 pages, 20985 KiB  
Article
The Effect of Different Fiber Reinforcement on Bearing Capacity under Strip Foundation on the Sand Soil: An Experimental Investigation
by Bilge Aksu Alcan and Semet Çelik
Appl. Sci. 2023, 13(17), 9769; https://doi.org/10.3390/app13179769 - 29 Aug 2023
Cited by 1 | Viewed by 991
Abstract
The aim of this study is to investigate the bearing capacity-settlement behavior of strip footing settling on sand soil randomly reinforced with glass fiber, basalt fiber, macromesh fiber, and four different hybrid fiber additives in which these fibers are used together. Model tests [...] Read more.
The aim of this study is to investigate the bearing capacity-settlement behavior of strip footing settling on sand soil randomly reinforced with glass fiber, basalt fiber, macromesh fiber, and four different hybrid fiber additives in which these fibers are used together. Model tests were carried out in the laboratory on the strip footing and placed on the unreinforced and reinforced sand with different fibers. In the study, model tests were carried out on seven types of randomly reinforced soils by using glass, basalt, macrame, and mixtures of these fibers as reinforcement. In the model tests, two different fiber contents, 1% and 2%, and two different fiber lengths, 24 mm and 48 mm, were used. Tests were carried out with Dr = 30% and 50% relative density, and reinforcement depths 1B, 2B, and 3B were selected. In addition, the photographs taken during the test were analyzed with the particle image velocimetry (PIV) method and the displacements on the soil were examined. As a result of the reinforced and unreinforced model tests, the highest ultimate bearing capacity was measured as 680 kPa from the tests with Dr = 50% relative density, 48 mm length, 2% contents, and 3B depth macromesh fiber reinforced. In hybrid fibers, the highest ultimate bearing capacity was measured as 495 kPa, with Dr = 50% relative density, 48 mm length, 2% contents, and 2D depth micromesh and basalt fiber-reinforced tests. In the reinforced tests, it was concluded that the most effective fiber on bearing capacity is macromesh fiber. It can be seen that in the PIV analysis, as the fiber additive increased, the settlements made by the foundation decreased under the same pressure. It has also been observed that adding reinforcement to the soil transfers the stresses occurring in the soil to a wider area. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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14 pages, 6322 KiB  
Article
Mechanical Behaviors and Numerical Simulation Analysis of a New Isolation System
by Bo Liu, Danguang Pan, Wanying Zhang, Yankai Lu and Guowei Ni
Appl. Sci. 2023, 13(13), 7667; https://doi.org/10.3390/app13137667 - 28 Jun 2023
Viewed by 648
Abstract
Finite element analysis is one of the key steps in evaluating the effectiveness of an isolation system. The aim of this paper is to research the mechanical properties of sliding and rolling friction systems and their application for isolating frame structures. A hybrid [...] Read more.
Finite element analysis is one of the key steps in evaluating the effectiveness of an isolation system. The aim of this paper is to research the mechanical properties of sliding and rolling friction systems and their application for isolating frame structures. A hybrid seismic isolation system is proposed, which aims to protect the superstructure by reducing dynamic response. The effect of different parameters on the friction coefficient of the isolation bearing was tested using a compression-shear testing machine, and the results showed that various parameters significantly affected the friction coefficient. In addition, a numerical analysis finite element model was established using SAP2000 software to compare the seismic isolation performance of the hybrid isolation system with that of traditional seismic-resistant structures. The results showed that the composite isolation system not only effectively reduced inter-story shear and acceleration, but also slightly enhanced the seismic isolation effect as the friction coefficient decreased. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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11 pages, 2493 KiB  
Article
Experimental Study on Maximum Dynamic Shear Modulus of Yangtze River Overconsolidated Floodplain Soft Soils
by Yifeng Zhou, Xing Xiao, Zhenglong Zhou and Qi Wu
Appl. Sci. 2023, 13(8), 4733; https://doi.org/10.3390/app13084733 - 09 Apr 2023
Viewed by 1178
Abstract
This study conducted experimental tests on the undisturbed Nanjing Yangtze River floodplain soft soil using the bender element instrument to determine the maximum dynamic shear modulus of the Yangtze River floodplain overconsolidated soft soil. The Gmax of floodplain soft soil with different [...] Read more.
This study conducted experimental tests on the undisturbed Nanjing Yangtze River floodplain soft soil using the bender element instrument to determine the maximum dynamic shear modulus of the Yangtze River floodplain overconsolidated soft soil. The Gmax of floodplain soft soil with different overconsolidated ratio OCR, initial effective confining pressure σ3c′, and void ratio e are discussed. The results indicated that Gmax reduced as e rose for given σ3c′ and OCR. In addition, an increase in OCR contributed to a gradual decrease in the decay rate of Gmax, while the Gmax decay rate is insensitive to the change of σ3c′. The void ratio-normalized maximum shear modulus Gmax/F(e) improved with the increase in the stress-normalized initial effective confining pressure σ3c′/Pa, whereas the growth rate gradually drops, and a power relationship is then obtained between Gmax/F(e) and σ3c′/Pa. Based on the regression analysis, a Gmax prediction method is established for reasonably characterizing Yangtze River floodplain soft soils with various over-consolidation states, initial stress conditions, and compactness levels, with a prediction error of less than 10%. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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13 pages, 5005 KiB  
Article
Sand Rubber Mixtures under Oedometric Loading: Sand-like vs. Rubber-like Behavior
by Pravin Badarayani, Bogdan Cazacliu, Erdin Ibraim, Riccardo Artoni and Patrick Richard
Appl. Sci. 2023, 13(6), 3867; https://doi.org/10.3390/app13063867 - 17 Mar 2023
Cited by 2 | Viewed by 1126
Abstract
Each year, the number of scrap tires disposed of in huge piles across the world continuously increases. Consequently, new recycling solutions for these materials have to be proposed. Among them, one possibility consists of shredding tires and mixing the obtained tire chips with [...] Read more.
Each year, the number of scrap tires disposed of in huge piles across the world continuously increases. Consequently, new recycling solutions for these materials have to be proposed. Among them, one possibility consists of shredding tires and mixing the obtained tire chips with sand, which can be used as alternative soils in various geotechnical applications, such as backfilling for retaining structures, slope and highway embankment stabilization, road constructions, soil erosion prevention, and seismic isolation of foundations. Such types of mixtures are highly heterogeneous due to the important difference in elasticity and deformability between the two constituents, which leads to complex mechanical behavior. In this article, the one-dimensional loading/unloading behavior of sand-rubber mixtures is investigated by laboratory strain-controlled experiments performed for different packing densities, particle sizes, rubber contents, and sand/rubber size ratios. After a global analysis of the increase of the packing deformation with the rubber fraction and the stress level, a novel criterion to classify the behavior of the mixture as sand-like or rubber-like was proposed, based on the concavity of the void ratio—log of vertical stress curve. The concavity increased with the stress level and the rubber fraction, up to the limits where the saturation of the voids due to their filling with rubber induces a rubber-like behavior. A simplified phase diagram, limited to the range of this study, is proposed. The one-dimensional confined stiffness and the swelling behavior were also analyzed. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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18 pages, 5642 KiB  
Article
Role of Diatom Microstructure in Determining the Atterberg Limits of Fine-Grained Diatomaceous Soil
by Yiqing Xu, Xianwei Zhang, Gang Wang, Xinyu Liu and Aiwu Yang
Appl. Sci. 2023, 13(4), 2287; https://doi.org/10.3390/app13042287 - 10 Feb 2023
Cited by 1 | Viewed by 1152
Abstract
The presence of diatoms in diatomaceous soil gives it geotechnical properties that are unusual compared with common clays. The most typical physical property of diatomaceous soil is its abnormally high Atterberg limits compared to fine-grained soil without diatoms. For diatomaceous soil, the Atterberg [...] Read more.
The presence of diatoms in diatomaceous soil gives it geotechnical properties that are unusual compared with common clays. The most typical physical property of diatomaceous soil is its abnormally high Atterberg limits compared to fine-grained soil without diatoms. For diatomaceous soil, the Atterberg limits are associated with many factors, such as diatom content, diatom crushing degree, etc. In the study reported here, it was ascertained that more diatoms lead to higher plastic and liquid limits. Once the diatoms are crushed, the plastic and liquid limits decrease. The pore fluid salt concentration barely influenced the Atterberg limits of diatomaceous soil. Additionally, the porous diatom microstructure and trimodal pore size distribution of diatomaceous soil were investigated via scanning electron microscopy, transmission electron microscopy, and mercury intrusion porosimetry. The underlying mechanism of abnormally high liquid and plastic limits of diatomaceous soil is revealed as the water stored in the special diatom microstructure. However, water in diatoms has no contribution to plasticity. Also discussed is the applicability of the current soil classification systems for diatomaceous soil. The findings of this study can help for a better understanding of Atterberg limits of diatomaceous soil and provide suggestions for the classification of diatomaceous soil. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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17 pages, 5490 KiB  
Article
Model Test Analysis of Groundwater Level Fluctuations on Karst Cover Deformation Taking the Monolithic Structure of Guilin as an Example
by Xuejun Chen, Xiaotong Gao, Hui Li, Mingming Xue, Xiaohui Gan and Yu Song
Appl. Sci. 2023, 13(3), 1747; https://doi.org/10.3390/app13031747 - 30 Jan 2023
Viewed by 1166
Abstract
Engineering practice and real-life cases show that the geological conditions of the Guilin overlying karst site are complex. In particular, the groundwater, which drives the accelerated formation of soil cavities, and the thickness of the overlying soil layer, which affects the speed of [...] Read more.
Engineering practice and real-life cases show that the geological conditions of the Guilin overlying karst site are complex. In particular, the groundwater, which drives the accelerated formation of soil cavities, and the thickness of the overlying soil layer, which affects the speed of the groundwater subsidence process. Therefore, this paper is based on a physical model to evaluate the effects of groundwater level changes caused by different factors on the deformation of karst cover. The model tests are simulated for different cover thicknesses (6 cm, 9 cm, 12 cm, 15 cm, 18 cm) under rainfall and other recharge, cavity supply, and drainage conditions at the same density (1.40 g/cm3) and initial water content (30%), respectively. The results show that with the increase of rainfall and other recharge time, the basic change trend of different cover thicknesses is that the infiltration curve changes faster at the beginning and slows down at the end, but the thicker the cover, the slower the overall deformation; at a certain rate of cavity recharge and drainage, the thicker the cover, the smaller the deformation caused by the fluctuation of groundwater level. The cavity recharge makes the cover displacement obvious, in the order of 0.304 cm, 0.173 cm, 0.118 cm, 0.068 cm, and 0.056 cm. After the formation of the cavity, the rainfall, other recharge, and the cavity supply and drainage accelerate the destruction and deformation of the soil body and the upward development of the cavity. The research results provide theoretical support for the subsequent prevention and control of karst collapse in covered karst areas, and have certain practical engineering significance. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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22 pages, 43358 KiB  
Article
Bearing Capacity of Shallow Foundations on Unsaturated Silty Soils
by Mehmet Ugur Yilmazoglu and Askin Ozocak
Appl. Sci. 2023, 13(3), 1308; https://doi.org/10.3390/app13031308 - 18 Jan 2023
Cited by 5 | Viewed by 1890
Abstract
In general, the ultimate bearing capacity (UBC) of shallow foundations on unsaturated soils is characterized by the conventional shear strength (SS) parameters in which saturated theories are applied. However, in this case, it is clear that the foundations designed using the obtained values [...] Read more.
In general, the ultimate bearing capacity (UBC) of shallow foundations on unsaturated soils is characterized by the conventional shear strength (SS) parameters in which saturated theories are applied. However, in this case, it is clear that the foundations designed using the obtained values from the saturated cases not be economical. In recent years, procedures have been developed to estimate the UBC of foundations on unsaturated soils, that take into account drained and undrained loading conditions. However, these studies generally concentrate on sandy soils. The validity of the results proposed in the literature should be tested for other soils. Therefore, this paper includes a conventional direct shear box (DSB) test to determine the unsaturated SS of statically compacted silty soil, and a series of model tests were performed to determine the foundation’s UBC. In the experimental model setup, the UBC values of different types and sizes of model foundations on silty soil layers with a different soil saturation degrees (SSDs)/matric suctions (MSs) and different void ratio values were measured. In addition, the soil-water characteristic curves (SWCCs) and SS parameters of unsaturated silt were obtained. Using the experimental results, a new equation is proposed for the characterization of the UBC of shallow foundations on unsaturated silty soils. Using this equation, the UBC of unsaturated soils can be determined based on the results of unconfined compressive strength tests (UC) measured on unsaturated soil samples and based on the degree of saturation and the fitting parameter. The results indicate that the measured bearing capacity values obtained via the model footing test, shows a good consistency with those obtained by the proposed equation. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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21 pages, 5007 KiB  
Article
Dynamic Characteristics of Post-Cyclic Saturated Loess
by Qian Wang, Yan Wang, Wenguo Ma and Dongwang Tao
Appl. Sci. 2023, 13(1), 306; https://doi.org/10.3390/app13010306 - 27 Dec 2022
Viewed by 1062
Abstract
Damage to soil structure caused by strong earthquakes is one of the main reasons for post-earthquake geohazard development. To investigate the nonlinear dynamic behaviors of the post-earthquake loess, a pre-shock reconsolidation test was designed to simulate the process of the loess undergoing earthquake [...] Read more.
Damage to soil structure caused by strong earthquakes is one of the main reasons for post-earthquake geohazard development. To investigate the nonlinear dynamic behaviors of the post-earthquake loess, a pre-shock reconsolidation test was designed to simulate the process of the loess undergoing earthquake and post-earthquake reconsolidation in a natural state. Furthermore, dynamic triaxial tests of the specimens before and after pre-shock action and consolidation stabilization with different over-consolidation ratios (OCR) were conducted to investigate the variety of the dynamic modulus and damping ratio of the saturated loess. The influence of pre-shock and reconsolidation on the dynamic behaviors was determined. Moreover, the mechanism of the changes after pre-shock and consolidation was discussed by combining the microstructure test results of soil samples before and after pre-shock and reconsolidation. The results suggest that the kinetic stiffness of the pre-shock saturated loess decreases significantly under the same consolidation conditions. The growth of the damping ratio-dynamic strain curve increases, and the deformation potential of the loess has a remarkable growth. With an increase in OCR, the dynamic elastic modulus after pre-shock increases continuously; however, the damping ratio decreases significantly. The dynamic stiffness increases and the deformation potential weakens significantly. The strong earthquake leads to the weakening of interparticle cementation, pore penetration, and structural reorganization in the local area, causes connecting of the macropores, and produces microfractures in the soil, which makes a significant decrease in the dynamic shear modulus ratio and an increase in the damping ratio of the loess, leading to the enhancement of soil dynamic nonlinearity and the attenuation of the dynamic strength. Moreover, the compaction effect of reconsolidation on the soil increases the interparticle friction and heals some microfractures, which leads to an increase in soil stiffness. This makes the maximum dynamic shear modulus and the maximum dynamic shear stress amplitude of the post-cyclic saturated loess perform at the same level compared with the natural loess without shock when the OCR equals three. However, the dynamic shear modulus and the damping ratio of the post-cyclic saturated loess are close to the natural loess when the OCR equals two. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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21 pages, 11149 KiB  
Article
Effects of Cement Treatment on Mechanical Properties and Microstructure of a Granite Residual Soil
by Xinxin Dong, Xiaohua Bao, Hongzhi Cui, Changjie Xu and Xiangsheng Chen
Appl. Sci. 2022, 12(24), 12549; https://doi.org/10.3390/app122412549 - 07 Dec 2022
Cited by 4 | Viewed by 1547
Abstract
A proper treatment of granite residual soil (GRS) in geotechnical practices requires both macro and microscopic evaluations. In this study, uniaxial and oedometric compression tests were conducted to investigate the mechanical properties of the saturated untreated and cement-treated GRS. Meanwhile, XRD, SEM, and [...] Read more.
A proper treatment of granite residual soil (GRS) in geotechnical practices requires both macro and microscopic evaluations. In this study, uniaxial and oedometric compression tests were conducted to investigate the mechanical properties of the saturated untreated and cement-treated GRS. Meanwhile, XRD, SEM, and MIP tests were conducted to identify the presence and types of C–S–H and the changes in the pore structure after cement treatment. The effects of cement treatment on the uniaxial compressive strength, secant modulus, compressibility, and vertical yielding pressure were revealed and the mechanisms of the soil structure to be modified through cement treatment were clarified based on the test results. A threshold volumetric cement content of 2–3% was determined based on the mechanical properties and microstructural characteristics of the saturated cement-treated GRS. Cement contents below this threshold would produce inadequate cementation between the soil particles. In contrast, cement contents above this threshold are considered inefficient because the transformation of the soil structure from single-porosity to dual-porosity increases the total porosity and retards the strength and stiffness gains. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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18 pages, 3836 KiB  
Article
Mechanical Properties and Engineering Applications of Special Soils—Dynamic Shear Modulus and Damping of MICP-Treated Calcareous Sand at Low Strains
by Xinlei Zhang, Jun Guo, Yumin Chen, Yi Han, Ruibo Yi, Hongmei Gao, Lu Liu, Hanlong Liu and Zhifu Shen
Appl. Sci. 2022, 12(23), 12175; https://doi.org/10.3390/app122312175 - 28 Nov 2022
Cited by 1 | Viewed by 1471
Abstract
Calcareous sand deposits are widespread along the shoreline in tropical and subtropical regions. Microbially induced calcite precipitation (MICP) treatment is a new method for improving the soil’s stiffness and strength. The small-strain shear modulus and damping ratio of MICP-treated calcareous sand, two critical [...] Read more.
Calcareous sand deposits are widespread along the shoreline in tropical and subtropical regions. Microbially induced calcite precipitation (MICP) treatment is a new method for improving the soil’s stiffness and strength. The small-strain shear modulus and damping ratio of MICP-treated calcareous sand, two critical parameters for predicting the dynamic behavior of soil, are little known. This study conducts a series of resonant column tests to investigate the dynamic characteristics of MICP-treated calcareous sand, emphasizing the influence of treatment duration and confining stress on the stiffness and damping characteristics. It analyzes the relationship between the initial dynamic shear modulus and unconfined compressive strength. In addition, empirical relationships between the reference shear strain and treatment duration or confining stress are provided. The results show that the normalized shear modulus G/G0 of MICP-cemented calcareous sand has a higher strain sensitivity than that of untreated sand, and the Hardin–Drnevich model can describe its attenuation pattern. The effective confining stress σc affects the degradation characteristics of the dynamic shear modulus of MICP-treated calcareous sand with a low cementation level; however, its impact decreases as the treatment duration increases. There is a linear relationship between the reference shear strain and confining stress. While the relationship between the reference shear stain and treatment duration is a power law. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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11 pages, 3160 KiB  
Article
The Shrink–Swell Process of the Granite Residual Soil with Different Weathering Degree in a Gully System in Southern China
by Honghu Liu, Jing Liu, Xianwei Zhang and Xinyu Liu
Appl. Sci. 2022, 12(21), 11200; https://doi.org/10.3390/app122111200 - 04 Nov 2022
Viewed by 1099
Abstract
The soil shrink–swell phenomenon produces crack networks and slope instability. However, few studies have involved the continuous shrink–swell process of granite residual soils. The objective of the study is to explore the shrink–swell process of weathered granite soils and its effects on gully [...] Read more.
The soil shrink–swell phenomenon produces crack networks and slope instability. However, few studies have involved the continuous shrink–swell process of granite residual soils. The objective of the study is to explore the shrink–swell process of weathered granite soils and its effects on gully development in southern China. The bulk density, soil water content (SWC), shrink–swell ratio (SSR), clay mineral content, and mechanical composition, etc., of soil samples from five soil layers (at depths of 0.3 m, 3.0 m, 7.0 m, 12.0 m, and 16.0 m) along a profile in Yudu County was analyzed. After quantifying the soil properties at different soil depths, we analyzed these data statistically in an effort to identify strong parametric relationships. The results indicated that some properties such as bulk density and shear stress increased with soil depth, while other soil properties, such as plasticity index and liquid limit, were inversely related to depth. Soil cohesion, the angle of internal friction, and shear stress were closely related to the SWC. Every 1% decrease in the SWC resulted in a shear stress reduction of 6.62 kPa. The SSR values exhibited significant variation between the three dry–wet cycles and were closely related to the bulk density values of our kaolin and montmorillonite samples. As an environmental factor, the SWC can trigger changes in internal soil properties such as shear stress and the SSR. Using these data and observations made during our field survey, it can be proposed that continuous shrink–swell variation in deep granite-weathering crust can result in crack formation and gully erosion. It can be inferred that crack development velocity and gully retreat rate may be affected by the soil’s shrink–swell process. Consequently, this information provides insight to understanding the mechanism of gully development in southern China. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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14 pages, 1635 KiB  
Article
Triaxial Experimental Study of Zinc Contaminated Red Clay under Different Temperature Conditions
by Jianqiang Wang, Yu Song, Shuaishuai Dong, Song Ding, Yukun Geng and Xiaotong Gao
Appl. Sci. 2022, 12(21), 10742; https://doi.org/10.3390/app122110742 - 23 Oct 2022
Viewed by 1159
Abstract
Temperature is one of the important factors affecting the mechanical properties of geotechnical soils, and its role in engineering construction in China cannot be underestimated. In order to study the effects of temperature and zinc contamination concentration on the mechanical properties of Guilin [...] Read more.
Temperature is one of the important factors affecting the mechanical properties of geotechnical soils, and its role in engineering construction in China cannot be underestimated. In order to study the effects of temperature and zinc contamination concentration on the mechanical properties of Guilin local red clay, a temperature-controlled triaxial shear test was conducted on Guilin red clay under three variables of temperature, zinc contamination concentration and surrounding pressure. The test findings revealed that there are significant differences in the effects of temperature, zinc contamination concentration and surrounding pressure on the mechanical properties of Guilin red clay. The stress–strain curves of the red clay at various temperatures, contamination concentrations and envelope pressures are of the strain-hardening type, and the deformation modulus showed a tendency to increase rapidly with increasing strain, then decrease rapidly, and finally, decrease slowly. With the increase of temperature, the cohesion of Zn-contaminated red clay increases, while the angle of internal friction increases and then decreases, both of which increase the shear strength of red clay. As the concentration of Zn contamination grows, the shear strength of the red clay increases, while the internal friction angle increases and then decreases, and the shear strength of the soil increases and then decreases. The shear strength of the Zn-contaminated red clay improved as the surrounding pressure increased. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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12 pages, 2726 KiB  
Article
Study on the Mechanical Strength of Calcium Oxide-Calcium Phosphate Cured Heavy Metal Zinc Contaminated Red Clay Soil
by Yu Song, Song Ding, Yukun Geng, Shuaishuai Dong and Hongbin Chen
Appl. Sci. 2022, 12(19), 10041; https://doi.org/10.3390/app121910041 - 06 Oct 2022
Cited by 1 | Viewed by 1282
Abstract
With the continuous improvement of the construction of the ecological economic system in the new era, the problem of heavy metal pollution has become an important issue in urban construction. In this paper, Zn2+ contaminated red clay is used as the research [...] Read more.
With the continuous improvement of the construction of the ecological economic system in the new era, the problem of heavy metal pollution has become an important issue in urban construction. In this paper, Zn2+ contaminated red clay is used as the research object, and calcium superphosphate and calcium oxide are used as curing agents to conduct the simultaneous test of unconfined compressive strength-resistivity. The mechanical properties and resistivity of the contaminated soil under different test conditions were analyzed to investigate their effects on the cured red clay. The results showed that different contamination concentrations showed different weakening effects on the unconfined compressive strength of red clay soils, and the unconfined compressive strength of cured soils increased significantly. The age of maintenance affects the unconfined compressive strength of cured soil, and the growth of unconfined compressive strength is most obvious in the age of 0–7 day. After that, it tends to be stable with the growth of age. The deformation modulus of contaminated soil before and after curing was reduced to different degrees. Before and after curing, the resistivity of contaminated soil decreased with the increase of ion concentration, and the resistivity of cured soil increased with the increase of curing agent incorporation rate under the same contamination concentration. The research results can enrich the soil treatment problem of heavy metal contaminated sites and provide theoretical support for the application of this type of curing agent in the field engineering of Zn2+ contaminated red clay soil. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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9 pages, 6411 KiB  
Article
Effect of Lead Ion Contamination on the Microstructure of Guilin Red Clay
by Yu Song, Shuaishuai Dong, Song Ding, Yukun Geng, Yaoyi Huang and Hui Li
Appl. Sci. 2022, 12(19), 9888; https://doi.org/10.3390/app12199888 - 01 Oct 2022
Cited by 1 | Viewed by 1289
Abstract
The heavy metal contamination of red clay in Guilin is a serious problem. Lead ions pollute red clay and have a series of effects, which affect the macroscopic properties of red clay. However, fundamentally, the effects occur because the internal microstructure of red [...] Read more.
The heavy metal contamination of red clay in Guilin is a serious problem. Lead ions pollute red clay and have a series of effects, which affect the macroscopic properties of red clay. However, fundamentally, the effects occur because the internal microstructure of red clay is eroded by Pb2+, which results in the change in the macroscopic properties of red clay. Therefore, we adopted a mercury injection experiment and used electronic microscope Pb2+ to explore the microscopic mechanism through which red clay is internally influenced. From the mercury injection experiment, we found that an increase in the concentration of Pb2+ increased soil pore diameter and volume, and that a higher heavy metal content of Pb2+ had a greater effect on red clay cementation. Using scanning electron microscopy, we found that when the micro-image magnification was 500 and 20,000 times, the inside of the red clay pore increased with the increase in the concentration of Pb2+, showing that the heavy metal within the microstructure damaged the red clay. The above two experiments showed that heavy metal ions increase the intergranular fractures of red clay, and the thickness of the double layer reduces, which results in the weakening of the interaction force between particles. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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Review

Jump to: Research

18 pages, 4292 KiB  
Review
Research Progress on the Influence of Thermo-Chemical Effects on the Swelling Pressure of Bentonite
by Jinjin Liu, Chuanqin Yao, Wenbo Su and Yizhe Zhao
Appl. Sci. 2023, 13(9), 5580; https://doi.org/10.3390/app13095580 - 30 Apr 2023
Viewed by 1469
Abstract
The swelling pressure of bentonite changes dramatically due to diffused nuclear radiation heat and underground osmosis, causing the failure of the buffer isolation layer in deep geological repositories for the disposal of high-level radioactive waste. A detailed overview of the relevant research results [...] Read more.
The swelling pressure of bentonite changes dramatically due to diffused nuclear radiation heat and underground osmosis, causing the failure of the buffer isolation layer in deep geological repositories for the disposal of high-level radioactive waste. A detailed overview of the relevant research results on the swelling pressure variation of bentonite under thermo-chemical effects is presented in this paper. The results showed that the values of the swelling pressure obtained by different test methods are dissimilar. The swelling pressure of bentonite decreased with the increasing pore solution concentration; nevertheless, the effect of temperature on the swelling pressure is still controversial. At the micro-level, crystal layer swelling and double- layer swelling are generally considered to be the main factors affecting the swelling pressure; the pore structure and water distribution of bentonite will change owing to thermo-chemical effects. At the macro-level, involving intergranular stress, a mechanical parameter was proposed to explain the mechanism of the changes in the swelling pressure of bentonite. Finally, future research directions for the study of the evolution of bentonite swelling properties under thermo-chemical effects are proposed, based on the current research results. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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35 pages, 6508 KiB  
Review
Diatomaceous Soils and Advances in Geotechnical Engineering—Part I
by Daniel Zuluaga-Astudillo, Juan Carlos Ruge, Javier Camacho-Tauta, Oscar Reyes-Ortiz and Bernardo Caicedo-Hormaza
Appl. Sci. 2023, 13(1), 549; https://doi.org/10.3390/app13010549 - 30 Dec 2022
Cited by 5 | Viewed by 2954
Abstract
Diatoms are microscopic algae with a skeleton called a frustule, formed chiefly of silica, and are found in almost all aquatic environments and climatic conditions. Diatomaceous soils (DSs) originate from frustule sedimentation. In civil works (design and construction), the uncommon values obtained from [...] Read more.
Diatoms are microscopic algae with a skeleton called a frustule, formed chiefly of silica, and are found in almost all aquatic environments and climatic conditions. Diatomaceous soils (DSs) originate from frustule sedimentation. In civil works (design and construction), the uncommon values obtained from DSs are not completely understood. There needs to be more knowledge about the strength and compressibility of DSs. The stability of these deposits is still being determined. Definitions of substances such as diatoms, diatomaceous soils, diatomaceous earth, diatomaceous oozes, frustules, and diatomite need to be clarified. This document references construction processes that face problems such as differential settlements, pile rebounds, and irregular pore pressures due to frustules. This review analyzes multiple sets of results regarding the grain size distribution, specific gravity, consistency, plasticity, compressibility, and shear strength of DSs. It is concluded that the particle size distribution of DSs generally classifies them as silts. Particles are modified by the imposition of stresses (frustule breakage), which impacts compressibility. Microfossils take up stresses, restrict strains, and cause sudden increases in compressibility when their yield stress is exceeded. Currently, their strain mechanisms need to be better understood. The Gs decreases with increasing frustule content, given the high porosity of the skeletons. The intraparticle pores of the frustules explain the high liquid limit (LL) of DSs. DSs can have high shear strengths and large yield surfaces due to the “interlocking” phenomenon and the interparticle contacts’ high frictional component caused by their rough surface and high silica content. Full article
(This article belongs to the Special Issue Mechanical Properties and Engineering Applications of Special Soils)
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