Dynamic Characteristics Of Soil Research Articles

Centrifuge modelling of the dynamic response of twin tunnels under train-induced vibration load

The impact of train-induced vibrations originating from underground tunnels has emerged as a significant environmental issue within urban areas. A multitude of studies, encompassing both numerical analyses and experimental investigations, have been undertaken to explore and address this concern. In the experimental tests, the dynamic characteristics of tunnels and soil has generally been studied using physical models with a single tunnel under a 1 g (gravity) environment. However, twin tunnels are commonly constructed in the field, and the stress of the soil is unrealistically simulated in 1 g models. In this paper, the dynamic characteristics of twin tunnels were studied by centrifuge testing. In this paper, results are presented from scaled model tunnel tests conducted at 50 g for four different conditions: a single tunnel, vertical twin tunnels with 60 mm spacing, horizontal twin tunnels with 60 mm and 120 mm spacing. Train load and sweep load were applied by a parallel pre-stressed actuator at the tunnel invert. Accelerometers were employed to gauge the dynamic response of both the tunnels and the surrounding soil. The experimental results illustrate that the interaction between twin tunnels has a clear amplification effect on the dynamic response of the loading tunnel, with the maximum peak particle acceleration (PPA) increasing by up to 43 %. This amplification phenomenon is reduced as the space between the twin tunnels is increased. The experimental results also indicate that the interaction between twin tunnels has a comparatively lower impact on the dynamic response of the surrounding soil when contrasted with the dynamic response of the tunnels themselves.

Dynamic deformation characteristics of lightweight soil based on Davidenkov model

The dynamic deformation characteristics of lightweight soil were studied using consolidated-undrained dynamic triaxial tests to predict its non-linear stress and strain behaviour under a traffic load. The results showed that the influence of confining pressure on the attenuation of the dynamic shear modulus ratio became significant with increasing expanded polystyrene (EPS) particle content or cement content. The attenuation curve of the dynamic shear modulus ratio was evaluated using Davidenkov model parameters, A, B and γ 0. It was proved that the parameter A was mostly affected by EPS particle content and confining pressure, with its value ranging between 1.1 and 1.85. The parameter γ 0 was affected by cement content and confining pressure, and its value ranged between 0.0007 and 0.0016. The parameter B was found to range between 0.38 and 0.55, in general. The relationship curves between damping ratio and dynamic shear strain revealed two forms, S shaped and bell shaped. The verification tests showed that the Davidenkov model could predict accurately the dynamic deformation characteristics of lightweight soil both under a changing stress state and under constant gradient loading conditions. These results provide a theoretical basis for determining the deformation of a lightweight soil subgrade under a traffic load.

Dynamic deformation characteristics and microscopic analysis of xanthan gum-treated silty soil during wetting process

The deformation characteristics of silty soils under vibrational loads can easily change due to the wetting process, leading to the failure of roadbed structures. Commonly used methods for improving silty soils in engineering often yield unsatisfactory economic and ecological outcomes. As an environment-friendly soil improvement material, Xanthan gum has broad application prospects and is therefore considered a solidifying agent for enhancing silty soil properties in the Yellow River Basin. In this study, a series of tests is conducted using a scanning electron microscope and a dynamic triaxial testing apparatus to investigate the microstructure and dynamic deformation characteristics of unsaturated silty soil with varying xanthan gum contents during the wetting process. The results show that xanthan gum effectively fills voids between soil particles and adheres to their surfaces, forming fibrous and network structures. This modification enhances the inherent properties of the silty soil and significantly improves its stability under dynamic loading. Specifically, with increasing xanthan gum content, the dynamic shear modulus increases while the damping ratio decreases. During the wetting process, as suction decreases, the dynamic shear modulus decreases while the damping ratio increases. Xanthan gum reduces the sensitivity of the dynamic deformation characteristics of the treated silty soil to changes in suction levels. Finally, based on the modified Hardin-Drnevich hyperbolic model, a predictive model for the dynamic shear modulus and damping ratio of treated silty soil is proposed, considering the xanthan gum content. These research findings provide a theoretical basis for the construction and maintenance of water conservancy, slope stabilization, and roadbed projects in the Yellow River Basin.

Retraction Note: Virtual reality research of the dynamic characteristics of soft soil under metro vibration loads based on BP neural networks

Retraction Note: Virtual reality research of the dynamic characteristics of soft soil under metro vibration loads based on BP neural networks

Experimental Study of the Static and Dynamic Characteristics of Lightweight EPS Composite Soils Treated with Cement

Experimental Study of the Static and Dynamic Characteristics of Lightweight EPS Composite Soils Treated with Cement

Effect and Mechanism of Freeze–Thaw Cycles on Static and Dynamic Characteristics of Expandable Polystyrene Lightweight Soil

Effect and Mechanism of Freeze–Thaw Cycles on Static and Dynamic Characteristics of Expandable Polystyrene Lightweight Soil

Seismic Microzonation Map of Chiang Mai Basin, Thailand

The seismic site effect which is controlled by local geological conditions is a key parameter of seismic hazards analysis. This paper presents an observational study of microtremor data to investigate the dynamic characteristics of soil in the Chiang Mai basin (Chiang Mai and Lumphun province), Northern Thailand. The Chiang Mai basin was formed on terrace sediments and alluvium sediments. The horizontal vertical spectral ratio (HVSR) analyses of ambient noise data at 101 sites in the basin were analyzed for an average smoothed HVSR curve to estimate the amplification factor and fundamental resonance frequency of each observation point. We also evaluated the shear wave velocity using the HVSR inversion technique based on the diffuse field assumption. Tests undertaken include a comparison of the HVSR of a significant earthquake that was detected at stations in the basin and a nearby bedrock site. The results indicate that the resonance frequency ranges between 0.15 - 0.4 Hz at sites having large thicknesses of soft sediments. The lowest resonance frequencies occur in the center of the basin, whereas higher resonance frequencies were observed in the areas of the shallowest bedrock in the west and east of the basin. It can be inferred that the western margin of the Chiang Mai basin is a steep slope, while the eastern margin of the basin is a low-angle west-dipping basement. The amplification factor ranges between 3 - 5 times, in the middle of the basin. Most of the Chiang Mai basin area is classified as site D soil (stiff soil) relative to alluvium sediments, and a region of class C soil (very dense soil) conforms to the terrace sediments located on the eastern edge of the basin. The soil classification is based on shear wave velocity (Vs30) determined by HVSR inversion. HIGHLIGHTS HVSR analysis and inversion of HVSR from 101 survey points in Chiang Mai basin The Chiang Mai basin area is at high risk from seismic amplification that amplifies a ground motion between 3 - 5 times in the middle of the basin at a dominant frequency range from 0.15 - 0.4 Hz The lowest Vs30 values location is in the middle of the basin classified as site class E (soft soil), while most of the basin area is classified as site D soil (stiff soil) corresponding to alluvium sediments. The class C soil (very dense soil) area conforms to the terrace sediments located on the eastern edge of the basin GRAPHICAL ABSTRACT

Evaluation of the dynamic soil characteristics of loam soils from MASW in Kazakhstan

Evaluation of the dynamic soil characteristics of loam soils from MASW in Kazakhstan

Experimental study on the effect of different cement content on the improvement of dynamic characteristics of seismic-prone poor soil.

The improvement of sandy soils with poor seismic properties to modify their dynamic characteristics is of great importance in seismic design for engineering sites. In this study, a series of dynamic tests on sandy soils sandy soils with poor seismic conditions were conducted using the GCTS resonant column system to investigate the improvements effects of different cement contents on dynamic characteristic parameters. The research findings are as follows: The cement content has certain influences on the dynamic shear modulus, dynamic shear modulus ratio, the maximum dynamic shear modulus, and the damping ratio of sandy soils with poor seismic properties. Among them, the influence on dynamic shear modulus is limited, while the damping ratio is significantly affected. The addition of cement to seismic-poor sandy soils significantly enhances their dynamic characteristics. The most noticeable improvement is observed when the cement content is 8%. Through curve fitting analysis, a relationship equation is established between the maximum dynamic shear modulus and the cement content, and the relevant parameters are provided. A comparative test between the improved soils and the remolded soils reveals that the addition of cement significantly improves the seismic performance of the poor soils. The recommended values for the range of variation of the dynamic shear modulus ratio and damping ratio are provided, considering the effect of improvement. These research findings provide reference guidelines for seismic design and engineering sites.

高速耕作条件下土壤离散元参数标定

For the problem of lacking reliable values of soil parameters required for dynamic simulation analysis of soil under high-speed tillage, no-tillage soil was taken as the research object and its parameters were calibrated using the discrete element method in this study. The Edinburgh Elasto-Plastic Adhesion (EEPA) model was determined as the soil contact model by obtaining the loading force-deformation relationship through uniaxial sealing compression tests. The regression equation was established using Plackett-Burman test and quadratic orthogonal rotation test, and the interaction effects were analyzed. The measured values of the pile angle and strain were obtained through the pile angle test and the uniaxial seal compression test, and the optimal solution was carried out. Further, the simulated values and the measured values under the optimal parameters were compared and verified, the result showed that the error values were all less than 1%. Finally, the soil model was used for high-speed tillage simulation analysis, and the obtained soil particle displacement and groove width were compared with the measured values. It was found that the ditch width error value was 3.04% and the soil displacement was basically the same. This study proved that the contact model parameters were relatively reliable, which could provide theoretical reference for the dynamic characteristics of soil during high-speed cultivation of no-tillage soil.

Seismic fragility curves of circular tunnels in saturated sand

This paper aims to derive seismic fragility curves for circular tunnels constructed in saturated sand. A bounding surface plasticity constitutive model is used to simulate the progressive accumulation of strains and the subsequent buildup of excess pore pressure in saturated sand under undrained conditions with cycles of loading. For comparative analysis, dynamic analyses under drained conditions are also conducted. The fully coupled numerical method, validated by centrifuge shaking table tests, provides a satisfactory explanation for the dynamic characteristics of soil–tunnel systems. On this basis, ten near-fault seismic motions are scaled incrementally to evaluate the dynamic performance under increasing seismic intensity for deriving the fragility curves. The investigation of the optimal intensity measure involves the correlation of structural response with peak ground acceleration/ velocity/ displacement and peak bedrock acceleration, respectively. The safety of tunnels is evaluated by the developed fragility curves, which account for the site effects of sand liquefaction on both structural response and fragility. The developed fragility curves also highlight the impacts of tunnel buried depth and sand relative density on the structural response and fragility of circular tunnels in liquefiable soils, providing a benchmark for the seismic hazard evaluations of underwater tunnels.

Experimental Study of the Dynamic Characteristics of PVA-Amended Expansive Soils

Expansive soils are distributed across a wide area in China, and land transport and surface construction will inevitably involve these soils. To mitigate the deficiencies of single-method expansive soil modification, it is highly important to adopt the use of polyvinyl alcohol (PVA) to improve expansive soils and enhance the strength and toughness of modified soils. In addition, solidification technology can be utilized for the resource utilization of expansive soils. In this study, triaxial testing is employed to evaluate the mechanical properties of solidified soil. When the confining pressure is the same and with increasing PVA content, soil particles and PVA combine to form a cemented substance, which fills the internal pores of the soil samples, enhances the cohesion between soil particles, and improves the bearing capacity of the soil. The stress–strain curve for the modified soil first increases and then decreases. The shear strength peaks at a PVA content of 3%. Based on the improved soil with a 3% PVA content, GDS dynamic triaxial tests were carried out to investigate the effects of different confining pressures and frequencies on the dynamic stress–strain curves, dynamic modulus of elasticity, and variation rule for the damping ratio of the improved soil. The results show that the dynamic stress–strain curve for the improved soil increases with increasing confining pressure and frequency and that the dynamic stress–strain backbone curves exhibit significant nonlinearities at different frequencies and circumferential pressures. The dynamic elastic modulus increases with increasing confining pressure and frequency and decreases gradually with increasing dynamic strain. The initial dynamic modulus of elasticity increases with increasing envelope pressure and frequency but is less affected by frequency, and the damping ratio decreases with increasing confining pressure and frequency. Soil treatment can improve the pore distribution, inhibit the extension of soil cracks, and enhance soil compactness.

Effect of site specific soil characteristics on the nonlinear ground response analysis and comparison of the results with equivalent linear analysis

Damages occurring during earthquakes may vary depending on the ground conditions in which the earthquake waves pass, the magnitude of the earthquake, the focal depth of the shaking and as well as the structural characteristics. Regional seismicity, ground movement and behavior of local soil conditions are important in earthquake-resistant building designs. Local site conditions consist of the layering, bedrock depth, and dynamic and topographic characteristics of soil that alter the bedrock waves through the soil profile during an earthquake. The change occurs in terms of amplitude, frequency and the time when the peak happens during the wave propagation. This initiates a big difference between the surface and bedrock motion. The behavior of the soil under cyclic loads resulting from seismic action is non-linear. This study aims to demonstrate the effects of strong ground motion by taking into account the nonlinear behavior of the soil layers. In addition, the results obtained from the equivalent linear and non-linear methods were compared. The results of the study showed that the characteristics of soil layers and strong ground motion (frequency content and duration) significantly affect the field response analysis and generally larger spectral parameters (about %20) have been obtained with the equivalent linear method compared to the nonlinear behavior. Finally, empirical models to estimate the soil amplification reflect different compared to the site specific analysis.

Damage constitutive model of lunar soil simulant geopolymer under impact loading

Lunar base construction is a crucial component of the lunar exploration program, and considering the dynamic characteristics of lunar soil is important for moon construction. Therefore, investigating the dynamic properties of lunar soil by establishing a constitutive relationship is critical for providing a theoretical basis for its damage evolution. In this paper, a split Hopkinson pressure bar (SHPB) device was used to perform three sets of impact tests under different pressures on a lunar soil simulant geopolymer (LSSG) with sodium silicate (Na2SiO3) contents of 1%, 3%, 5% and 7%. The dynamic stress–strain curves, failure modes, and energy variation rules of LSSG under different pressures were obtained. The equation was modified based on the ZWT viscoelastic constitutive model and was combined with the damage variable. The damage element obeys the Weibull distribution and the constitutive equation that can describe the mechanical properties of LSSG under dynamic loading was obtained. The results demonstrate that the dynamic compressive strength of LSSG has a marked strain-rate strengthening effect. Na2SiO3 has both strengthening and deterioration effects on the dynamic compressive strength of LSSG. As Na2SiO3 grows, the dynamic compressive strength of LSSG first increases and then decreases. At a fixed air pressure, 5% Na2SiO3 had the largest dynamic compressive strength, the largest incident energy, the smallest absorbed energy, and the lightest damage. The ZWT equation was modified according to the stress response properties of LSSG and the range of the SHPB strain rate to obtain the constitutive equation of the LSSG, and the model's correctness was confirmed.

Study on Mechanical Properties Subjected to Monotonic and Dynamic Loads of Loessal Soil in Songyuan City

In this paper taking loessal soil of Songyuan in Jilin province as the research object，static and dynamic triaxial tests were conducted to investigate the effects of water content and confining pressure on dynamic characteristics of loessal soil. The test results showed that: (1) Under monotonic loading, the deformation of loessal soil exhibits two situations: strain hardening and strain softening, and the deformation behavior is influenced by water content and confining pressure. The static strength decreases with the increase of water content and increases with the increase of confining pressure. (2) The cumulative plastic strain of loessal soil under dynamic load exhibits three modes: plastic shakedown, plastic creep, and incremental collapse. Existence of critical dynamic stress results in significant differences in the cumulative plastic strain of soil. (3) The cumulative plastic strain of soil samples is influenced by water content, confining pressure, and dynamic stress amplitude, low confining pressure, high water content, and high dynamic stress amplitude are adverse to the plastic stability of loessal soil. Based on experimental results, predict the range of critical dynamic stress. The research results have reference value for the evaluation of dynamic deformation stability of settlement of subgrade constructed in the loessal soil.

Dynamics of Tropical Peatlands Characteristics and Carbon Stocks as Affected by Land Use Conversion and Ages of Land Use in Riau Province, Indonesia

The dynamics and patterns of relationships between the characteristics of Indonesian tropical peat involving a function of time (ages of land use) in the context of land conversion have yet to be widely reported. The effects of tropical peatland use change are generally discussed regarding C emissions, with the limited literature identifying dynamic soil characteristics as these changes occur. This study used a survey method. We identified the physical, chemical, and C stock characteristics of peat in forest locations, oil palm plantations with a land use age of 0-5 years,>5-10 years,>10 years, and agricultural land with a land use age of 0-5 years and >5-10 years to find out the dynamics of soil characteristics. Land use changes from peat swamp forests to oil palm plantations and agricultural land, and the longer age of land use results in an increase in BD (especially at the top layer), ash content, pH, Total-N, total-P2O5, total-K2O, but there was a decrease in water content, fiber content, Organic-C, E400/E600, and soil C stocks. The alignment of economic, social, and ecological interests was directed to water and land management by regulating the area’s hydrological system and increasing peat stability.

Comparative Study of the Seismic Response Characteristics of Three Special Soils

Because of its special material composition, formation environment and special structure, special soil usually shows different seismic response characteristics from general soil, and sometimes causes serious seismic disasters. Therefore, the study of seismic response characteristics of special soil has important practical significance for engineering construction and disaster prevention in special land areas, and a site seismic response analysis is an important way to study the impact of site conditions on ground motions. Based on the existing research work, the uniform and single ideal soil layer profiles of three special soils are established, and the seismic response analysis program of the soilquake soil layer is used to study the effects of the dynamic shear module ratio, damping ratio and shear-wave velocity of soft soil, loess and laterite on the characteristic period and platform value of the design response spectrum under different input ground motion intensities. At the same time, three typical actual drilling data values are selected to establish the calculation model of the site soil layer. On the basis of the seismic response analysis and calculation of the soil layer, three special soil dynamic characteristics are compared from the aspects of peak acceleration and characteristic parameters. Based on the research results of this paper, the recommended values of the dynamic shear module ratio and damping ratio of three special soils are given. This work has important reference value for seismic design in soft soil, loess and laterite areas, and also enriches the research results of soil dynamic parameters.

Effect of saturation on dynamic characteristics of collapsible gypseous soil using cyclic triaxial testing

Studying the unsaturated gypseous soils behavior may lead to more understanding of the gypseous soil problems associated with unsaturation under the effect of the vertical vibrations. The purpose of this paper is to assess the suitability of unsaturated gypseous soil as a machine foundation soil. Moreover, such a purpose is considered beneficial in assessing appropriate methods for studying the characteristics and the behavior of unsaturated gypseous soils such as soil elastic modulus parameters, compressibility parameter, waves velocities, and amplitude axial strain for cyclic loading parameters under different with degree of saturation. The tests were performed for conditions 35% and 70% relative density of natural gypseous soil under 1.0 Hz and 2.0 Hz cyclic frequency at degrees of saturation (30%, 60%, and 80%), and fully saturated gypseous soil to investigate the gypseous soil behavior. It was found the values of the elastic modulus and wave velocities at degree of saturation 60% for different number of cycles and frequency increased with decrease of the strain and compressibility. Then, it began to decrease gradually at the saturation degree 80% and 100%, respectively. The best results based on strength consideration were obtained at 60% saturation, and the lowest strength was found when the soil was 100% saturated, for both load frequencies 1, and 2 Hz. The load frequency 1 Hz gave higher values than cyclic frequency 2 Hz of elastic modulus and wave velocities, while the number of cycles was less at the same time and for different degrees of saturation.

Dynamic characteristics of carbonate saline soil under freeze–thaw cycles in the seaonal frozen soil region

The occurrence of road damage, such as frost heave and thaw settlement, is highly likely in saline soil subgrades in seasonally frozen areas due to traffic loads and freeze–thaw cycles (FTC). In this regard, a low-temperature dynamic cyclic triaxial test was conducted to investigate the dynamic characteristics of carbonate saline soil under traffic load. The study explores the impact of salt content (SC) and the number of FTC on the backbone curves, the dynamic shear modulus (TDSM), and the damping ratio (TDR) characteristics of saline soil. An improved H-D model was employed to derive the dynamic backbone curve, and TDSM and TDR empirical formulas were established.The study's results show that the backbone curves of saline soil exhibit typical nonlinear and strain-hardening characteristics. Additionally, a higher salt content or more FTC result in a smaller TDSM and a larger TDR of the remodeled saline soil. TDSM shows an inverted “S” shape with an increase in cyclic shear strain, and the decay rate of TDSM increases when the cyclic shear strain is greater than 10-4 and less than 10-3. The decay rate of TDSM decreases and approaches a constant value after the cyclic shear strain exceeds 10-3. The decay of TDSM of low-salt soils (salt content less than 0.5%) mainly occurs in the first six freeze–thaw cycles. In contrast, the decay of TDSM of high-salt soils (salt content more than 0.5%) remains highly dependent on the number of FTC. Furthermore, TDR show an flat “S” shape with an increase of cyclic shear strain. The rate of increase in TDR of low-salt soil decelerates after six FTC, while the rate of increase in TDR of high-salt soil decelerates after nine FTC. Finally, empirical formulas for TDSM and TDR were established by varying the fitting parameters. The results of this study provide a useful reference for engineering projects in regions that encounter seasonal freezing. These findings will assist engineers in the design and construction of structures that can withstand the detrimental effects of traffic loads and FTC.

Experimental investigation for dynamic characteristics of paraffin-graphite based CPCM (composite phase change material) amended expansive soil under dry-wet cycles

Expansive soils are known to exhibit complex behavior under varying moisture and stress conditions, leading to soil cracking and instability. In this study, the effects of composite phase change material (CPCM) on the dynamic characteristics of expansive soils before and after dry and wet cycles were investigated. Further, the soil with and without CPCM amendment was also subjected to dry-wet cycles so as to monitor cracking phenomenon. Dynamic triaxial tests were conducted to evaluate the damping ratio and elastic modulus of expansive soil amended with CPCM. For interpretation of the cracking and dynamic properties of CPCM amended soil, laser thermal conductivity and electron microscope scanning tests were conducted. The results showed that the incorporation of CPCM material effectively inhibited soil cracking by reducing the temperature gradient difference within the soil and actively regulating the temperature distribution. Moreover, the CPCM amended expansive soil demonstrated better stability under the combined effect of alternating load and wet and dry cycles. The dynamic modulus of elasticity of the 10% CPCM amended soil was found to be about three times that of the bare soil. Additionally, the CPCM material improved the soil structure and reduced the damping ratio and the generation of pore water pressure in the expansive soil. Overall, this study demonstrates the effectiveness of using CPCM materials to improve the dynamic characteristics and stability of expansive soils, making it more suitable as roadbed filler.