最新刊期
期 1 ， 2024
- 摘要：The loess with different thickness is in the humid-thermal coupling environment of rainfall-evaporation for a long period of time, which is very prone to induce the generation of cracks in the loess, significantly weakening the structural and integrity of the loess, thus affecting the construction of the project area. Therefore, it is necessary to study the effect of soil thickness on the cracking characteristics of loess under the action of wet dry cycles. In this paper, a series of indoor wet dry cycle tests were carried out to record the water content change and crack development of the specimens in real time, and the crack network was analyzed by using digital image processing technology combined with fractal dimension. The test results show that: the different evaporation paths and water contents lead to inconsistent water evaporation rate of the soil, and the greater the thickness of the loess, the slower its water evaporation rate; interfacial friction affects the cracking process of the soil, and the thicker the soil, the slower the development of cracks, and the lower the complexity of the crack network. As drying proceeds, the interfacial friction gradually decreases and the soil shrinks significantly. The dry-wet cycle effect will lead to the reassembly of soil particles, accelerate the water evaporation process, and the soil surface will deteriorate continuously. The results of the study can provide some guidance for the prevention and control of geologic hazards in the Loess Plateau region.关键词：dry-wet cycles;soil thickness;fracture characteristics;fractal dimension;friction
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发布时间：2024-01-18 - 摘要：Freeze-thaw acting is an important factor that can’t be ignored in engineering disasters such as loess slope slump and roadbed subsidence. Water retention behaviour is the key physical property for analyzing the hydraulic-mechanical properties of unsaturated loess, and it needs to be further studied that how freeze-thaw cycle affects water retention behaviours of loess. This test took intact loess after freeze-thaw cycles as research objects and studied how both the number of freeze-thaw cycles and the water content before freeze-thaw affect the soil-water retention curve (SWRC) and its characteristic parameters. The results show that the effect of freeze-thaw cycles on SWRC is fluctuating, and the degree of influence is controlled by the number of cycles and the initial water content before freeze-thaw. The relationship between saturation and ratio of suction (ratio between suction and air-entry value) can be normalized under different freeze-thaw conditions. By establishing quantitative relationship between the air-entry value and the structure index, a modified water-retention model was proposed to consider the effect of freeze-thaw cycles uniformly. The effect of freeze-thaw cycle conditions on the SWRC of intact loess is preliminarily confirmed, which can be reflected by the change of air-entry value caused by the change of soil structure index.关键词：intact loess;freeze-thaw cycles;water retention behaviours
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发布时间：2024-01-18 - 摘要：Loess has porous metastable structure and water sensitivity, and is prone to collapse when it encounters water. The disintegration of loess is one of the main factors that promote soil erosion, collapse, landslide and other geological disasters in the Loess Plateau. As a low cost and convenient material, cement improved loess (CIL) is widely used in loess foundation and slope engineering, but there are few researches on its anti-disintegration. The disintegration behavior of loess before and after the improvement was analyzed through the laboratory disintegration test and scanning electron microsope(SEM) test under the condition of CIL and different content, and the improvement effect and mechanism of cement on loess disintegration were explored. The results show that cement can greatly improve the anti-disintegration ability of loess. At low content, CIL still has a complete disintegration process, but cement can fill the intergranular pores and hinder water transport. Meanwhile, cement hydration and its interaction with loess particles can enhance intergranular cementation, thus delaying the disintegration process of loess. With the increase of cement content, the anti-disintegration effect is more obvious, and the cumulative disintegration component is almost 0. The minimum cement content of soil sample without disintegration is 3%. The results are of great significance to the study of erosion resistance of loess and the design of disaster prevention engineering.关键词：loess;cement;the property of disintegration;improved soil;SEM
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发布时间：2024-01-18 - 摘要：The prediction of the dynamic stress-strain relationship of compacted loess is essential in the projects of gully reclamation for farming and cutting mountains for city building in Loess Plateau. It is still difficult to predict the behaviors. To fill the gap, this paper formulates a bounding surface plasticity model for compacted loess subjected to cyclic loading. Specifically, a plastic modulus for cyclic loading is proposed to reflect the behaviors of accumulated strain, and an updated mapping rule is introduced. Furthermore, the influence of confining pressure and cyclic stress ratio on stress-strain relationship and modulus is shown by several case studies, which is verified by experimental tests of compacted loess. The results show that the plastic modulus reflects accumulated strain of compacted loess.The constitutive model considers the effect of cyclic stress ratio on dynamic stress-strain relationship and modulus of compacted loess because of the proposed plastic modulus and updated mapping rule. The results can give reference for analysis of long-term deformation of loess-filled foundation.关键词：compacted loess;cyclic loading;stress-strain;constitutive model;plastic modulus
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发布时间：2024-01-18 - 摘要：A series of studies were carried out to examine the strength and stress-strain characteristics of cement-treated heavy metal-contaminated soil, with an emphasis on the actual engineering issue of heavy metal-contaminated loess and its deterioration.The research focused specifically on cement-treated zinc-contaminated loess, taking into consideration the influence of cement content and curing time. The experiments aimed to analyze the changes in the stress-strain curve, unconfined compressive strength, failure strain, and deformation modulus, and to construct a model of the stress-strain behavior under unconfined conditions. Additionally, a stress-strain model was developed for cement-treated zinc-contaminated loess under no-lateral limit conditions.The study reveals that the stress-strain curve of cement-treated zinc-contaminated loess exhibits strong softening behavior, resulting in brittle specimen damage. The curve can be divided into four stages: elasticity, elastic-plasticity, stress reduction, and residual stability. Furthermore, the study finds that with an increase in curing time and cement content, the unconfined compressive strength improves while the failure strain generally decreases. The deformation modulus shows a non-linear relationship with the unconfined compressive strength. A stress-strain model is constructed to describe the non-linear relationships among curing time, cement content, deformation modulus, and unconfined compressive strength accurately. Specifically, the model considers the effects of curing time and cement content on the stress-strain behavior of cement-treated zinc-contaminated loess under uniaxial pressure.Overall, these findings contribute to understanding the strength and stress-strain characteristics of cement-treated zinc-contaminated loess and provide valuable insights for addressing heavy metal contamination in loess engineering applications.关键词：solidification;zinc-contaminated loess;heavy metal;deformation modulus;unconfined compressive strength;stress-strain curve
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发布时间：2024-01-18 - 摘要：The accuracy of the results is influenced by capacitive components. This paper focuses on loess in the Yichuan region and establishes the relationship between unsaturated loess matrix suction and complex resistivity parameters based on complex resistivity tests and soil-water characteristic determinations. It reveals the variation patterns of their spectral characteristics and derives formulas for loess saturation degree and complex resistivity. The research results indicate that the excitation frequency is negatively correlated with the amplitude and phase of complex resistivity. When the frequency is less than 1 000 Hz, the amplitude and phase of loess complex resistivity fluctuate significantly, stabilizing gradually after it exceeds 1 000 Hz. With the increase of matrix suction, the amplitude, real part resistivity, and imaginary part resistivity of loess gradually increase, with their correlation influenced by the applied frequency. Loess capacitance and dielectric constant decrease with the increasing matrix suction. A loess saturation degree-complex resistivity model is established using the real part resistivity and imaginary part resistivity, and the model can be used for monitoring moisture changes in loess. The research results provide new methods and perspectives for utilizing the frequency dispersion characteristics of loess in geological disaster monitoring.关键词：loess;complex resistivity;spectral characteristics;matric suction;saturation-complex resistivity model
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发布时间：2024-01-18 - 摘要：Under the background of global warming and "carbon peaking and carbon neutrality" strategy, vegetation slope protection has become a potential means to reinforce the slope of negative carbon emission and errosion control. The development of vegetation roots can change the soil structure and hydraulic characteristics, and then affect the stability of slope. Although some experimental studies have explored the effects of vegetation on soil hydraulic characteristics under specific conditions, the general law that vegetation roots change soil hydraulic characteristics under different conditions is not clear.In this paper, the research on vegetation transpiration, root physical function and root biochemical function are collected and reviewed, the mechanism of the effect of vegetation roots on soil hydraulic characteristics is analyzed and summarized, and the available experimental data are statistically analyzed. It is pointed out that the change of hydraulic characteristics of soil by vegetation roots depends on the relative contributions of transpiration, physical and biochemical processes of roots, at the same time by the root type, soil type and growth stage and other factors. Therefore, the effect of vegetation roots on soil hydraulic characteristics is very complex, and more comprehensive and extensive researches are needed to reveal the mechanism of vegetation slope protection. Finally, the blank and future research trend of the effect of vegetation roots on soil hydraulic characteristics are discussed.关键词：vegetation roots;SWRC;hydraulic conductivity;soil suction;plant transpiration
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发布时间：2024-01-18 - 摘要：The effects of Cu2+ on the physicochemical and structural characteristics of undisturbed loess were studied in order to formulate effective strategies for environmental protection, soil pollution prevention and remediation, and to provide theoretical support for the engineering construction of contaminated sites. The particle size distribution, CaCO3 content and pH value of Cu2+ contaminated loess samples were determined. The SEM images and particle size contents of the samples were obtained by scanning electron microscopy and laser particle size analyzer. The influence mechanism of Cu2+ on the microstructure of undisturbed loess was analyzed by means of fractal theory. The compression test of Cu2+ contaminated undisturbed loess was carried out, and the comprehensive structural potential of the sample was analyzed. The results show that with the increase of Cu2+ content, the clay content increases first and then decreases, and then increases and then decreases, while the powder content decreases first and then increases, and the sand content remains unchanged. The content of CaCO3 decreased linearly. The pH value decreases rapidly at first, and then remains unchanged. The comprehensive structural potential of the contaminated loess samples first increased and then decreased, and then increased and then decreased. In general, the incorporation of heavy metal Cu2+ leads to the decrease of soil pH value, the dissolution of the main cementing material calcium carbonate, and the change of the form and composition of clay aggregates due to the electrostatic attraction and van der Waals forces between clay particles, thus affecting the compactness and structural strength of soil.关键词：Cu2+;undisturbed loess;SEM images;comprehensive structural potential;particle size distribution;fractal theory
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发布时间：2024-01-18 - 摘要：In loess formations, multiple layers of reddish ancient soil often alternate. Due to their relatively high hardness, they are resistant to collapsing when exposed to water, which significantly impacts the measurement results of the collapsibility of loess formations. However, there is currently a lack of research on the controlling role of ancient soils in collapsibility, leading to a lack of theoretical basis for making scientific decisions on the collapsibility of geological formations.To address this gap, this study compiled the results of inundation tests in the Loess Plateau region, analyzed the indoor and outdoor differences in collapsibility characteristics in different areas, and focused on large-scale inundation tests in two experimental sites in Xi’an. Various aspects were measured under different test conditions, including moisture diffusion in the soil, moisture content changes, soil pressure variations, and cumulative collapsibility.The final results indicate that paleosollayers hinder the collapsibility process by impeding water infiltration and preventing the transmission of deep-seated collapsibility to the surface. This leads to a positive correlation between the measured collapsibility values and the number of ancient soil layers. This study aims to provide insights into the self-weight collapsibility mechanisms in loess formations where ancient soil layers are commonly found.关键词：Paleosol;inundation test;collapsibility;collapsibility coefficient;loess
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发布时间：2024-01-18 - 摘要：Ten cases of ground subsidence in the study area are taken as the research object. Based on field investigations and combined with the geological environment conditions and engineering geological data of the study area, the basic geological background and ground subsidence development conditions of the study area are obtained. Several types of ground subsidence in the study area are comprehensively summarized, and the causes, spatiotemporal distribution characteristics, and collapse formation mechanisms of different types of ground subsidence are analyzed. The finite difference software FLAC3D was used to simulate the development process of ground collapse under tunnel excavation, building houses, groundwater level rise, and heavy rainfall conditions. The formation mechanism of ground collapse in the study area was obtained by analyzing the stress and strain inside the soil layer, as well as the displacement of the surrounding soil and surface of the tunnel. The research results indicate that the construction of residential buildings increases the overlying load, and the rise of groundwater level causes deformation of the soil around the cavern, leading to the expansion of the cavern. Under the influence of seasonal heavy rainfall, the surface undergoes significant settlement.关键词：collapse;mechanism;groundwater;heavy rainfall;numerical simulation
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发布时间：2024-01-18 - 摘要：The long-span pile foundation in the development project of the superstructure of the urban depot has the characteristics of larger vertical bearing of a single pile, and the soil within the large span between the piles is lesser stressed. Taking the long-span pile foundation of a depot of Xi’an Metro as the research object, artificial collapsible loess is prepared as a similar material. An indoor model test of long-span pile foundation in collapsible loess layer was carried out. The load transfer mechanism and deformation law of long-span pile foundation in collapsible loess layer were studied. The results show that the prepared artificial collapsible loess is close in nature to the original loess on site, which can achieve good results in the application of model tests. When the long-span pile foundation is not flooded, the load-settlement curve is steep, and the axial force of the pile body decreases significantly near the top of the pile. When the ultimate bearing capacity is not reached, the pile top settles and the pile end resistance increases linearly. After the loess is flooded, the axial force of the pile body is distributed in a "D" shape along the direction of burial depth. With the increase of water immersion time, the pile top settlement and pile end resistance first slowly increased and then increased significantly, and the neutral point position continued to move to the lower part of the pile body.关键词：collapsible loess;pile foundation;model testing;negative friction resistance
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发布时间：2024-01-18 - 摘要：The Luozhuang Group 3 landslide in Xiaoling Town, Zhashui County, is the focus of the present study.Geotechnical tests are performed indoors based on the geological survey in the field. By means of large-scale direct shear test and numerical simulation, the shear mechanical properties of sliding zone soil under different water content conditions are analyzed and studied. On this basis, the formation mechanism and deformation process of rainfall-induced accumulation landslide are revealed. The large-scale direct shear test shows: in the early stage of the test, the shear stress and shear displacement are linear, and the curve shows nonlinear characteristics with the increase of shear displacement. When the other test conditions are the same, the shear stress is negatively correlated with the water content. When the water content is the same, the shear stress increases with the increase of the normal load. The numerical simulation results show that the accumulation layer slope is prone to instability under the action of rainfall factors, with the continuous increase of rainfall intensity and duration, the soil moisture content increases or is prone to damage after saturation, and the slope stability coefficient decreases continuously. Under the condition of rainfall, the deformation of the landslide body of the accumulation layer is relatively strong, and its deformation process generally undergoes three stages, creep deformation - accelerating deformation - sliding failure. The form of failure movement is mainly push-type, which has a destructive effect on the threat object through the pushing effect, resulting in personnel and property losses. The research results have certain reference significance for the mechanism research and disaster prevention and mitigation of colluvial landslides in Qinba Mountain area.关键词：accumulation layer landslide;rainfall;large direct shear;numerical simulation;landslide mechanism
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发布时间：2024-01-18 - 摘要：The micro-pile has the advantages of fast and convenient construction and small disturbance, and has been used in the rapid treatment of loess landslide.In order to reveal the dynamic response law of loess landslide supported by micro pile, based on the dynamic visco-elasto-plastic constitutive model (VEP model), the seismic dynamic interaction mechanism between micropile and landslide is studied, and the reasonable pile spacing is discussed. The results show that the numerical calculation is close to the physical model test. The calculation results of VEP model after excitation are sensitive to the magnitude of earthquake. The model considers the visco-elastic-plasticity of soil and can reasonably reflect the displacement law of slope under earthquake. Under the action of the earthquake, the pile body of the micro-pile group produces bending shear failure, and the main failure position is located at 2~4 times the pile diameter above and below the sliding surface; it is suggested that the column spacing of micro pile group should be 5~7 times the pile diameter, and the row spacing should be 3~4 times the pile diameter.The research results can provide a basis for seismic design and numerical analysis of loess landslide prevention and control under earthquake.关键词：micro pile;numerical simulation;soil dynamic characteristics;pile spacing optimization;landslide;earthquake
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发布时间：2024-01-18 - 摘要：In view of the defects of conventional concrete such as slow setting, long construction period and complex construction, the new idea of slope reinforcement by quick-setting polymer micro anti-slide piles is put forward, and model tests and numerical simulation of sand slope reinforced by quick-setting polymer micro anti-slide piles are carried out. The results show that when the Mohr-Coulomb strength parameter is converted to Drucker-Prager strength parameter in numerical simulation, the value of the Lode angle is set to 0, which can reflect the strength characteristics of the slope soil more accurately. The displacement, deformation development and failure characteristics of the slope under different conditions obtained by numerical simulation are in good agreement with the experimental results, which verifies the accuracy of the numerical simulation to a certain extent. After the 5th level of horizontal thrust (1 500 N), the measured displacement of the slope foot, slope middle and slope top reinforced by a single row of polymer micro anti-slide piles decreased by 33.4%, 33.3% and 33.3%, respectively, compared with that before reinforcement, while the measured displacements of the slope foot, slope middle and slope top reinforced by double-row piles decreased by 55.9%, 53.4% and 43.4%, respectively. Before reinforcement, the slope surface showed wavy deformation characteristics, and the deformation was significantly improved after reinforcement. The pile body in single-row pile condition breaks when the horizontal thrust reaches 1 800 N, while the back pile in double-row pile condition breaks first when the horizontal thrust reaches 2 400 N. The conclusion of the study verifies the effectiveness and feasibility of fast-setting polymer micro anti-slide piles in slope reinforcement.关键词：quick-setting polymer;micro anti-slide pile;sand slope;reinforcement effect;model test;numerical simulation
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发布时间：2024-01-18 - 摘要：This study, an outdoor flume model test, was to model the movement of different-diameter boulders under the complete fluid-solid coupling with different-density landslides, analyze the movement patterns of boulders in landslides, the factors influencing the movement of boulders, and the force condition of boulders in a landslide and also explore the effect of the debris flow density and boulder diameters on the velocity of the boulders in landslides. The study found that the movement of boulders may be rolling, leaping or sliding, which is related to their density and diameter. That is, the greater the boulder’s diameter and the smaller its velocity, the simpler its movement pattern in the landslide, it is more likely to roll, the better its following behaviour in the landslide; also, it is more likely for the speed ratio (n) to approach 1. The study showed that the boulder diameter affects boulder velocity more greatly than the landslide density.关键词：debris flow;spherical boulders;flume model test;movement pattern
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发布时间：2024-01-18
Engineering Geological Disasters
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