Dynamic Characteristics Of Soil Research Articles

Experimental Study on Geosynthetic Reinforced Soil Dynamic Characteristics under Cyclic Loading

The technology of geosynthetic reinforced soil has been widely used in the structural strengthening of highway subgrade. Under the action of long-term vehicle cyclic loading, geosynthetic reinforced soil can effectively improve the bearing and deformation resistance capacity of the subgrade, improve the long-term stability of the highway structure and prolong the service period of the road. At present, the quasi-static method to design the geosynthetic reinforced subgrade under the action of traffic load is not perfect enough, the research on dynamic property, design theory and parameters still lags far behind engineering practice and technology development. In this paper, we investigated the dynamic triaxial tests in laboratory with different kinds of soils (clay and silt), different confining pressures (50 Kpa, 100 Kpa and 150 Kpa), and different reinforcement layers (0 layer, 1 layer and 2 layers) to show the changes and influencing factors of dynamic elastic modulus and damping ratio. The experimental results will provide the basis for the parameter choice of geosynthetic reinforced subgrade with the influence of traffic load.

RETRACTED ARTICLE: Virtual reality research of the dynamic characteristics of soft soil under metro vibration loads based on BP neural networks

In this paper, in order to research the dynamic characteristics of soft soil under metro vibration loads, the mathematical expression of metro vibration loads is obtained. According to the loading form, drainage requirement and vibration frequencies of the actual situation, the corresponding experiment is conducted through indoor dynamic triaxial equipment. Then, the dynamic characteristics of experimental results are analyzed. An empirical formula is proposed to compute the dynamic characteristics of soft soil. Then, the computational results obtained by empirical formula are compared with those of the experimental. They are consistent with each other, and the results show that empirical formula is reliable to compute the dynamic characteristics of soft soil. Then, based on the verified empirical formula, the dynamic characteristics such as the vertical strain and pore water pressure with different CSR are also computed and compared. With the increase in CSR, the dynamic characteristics will be larger when the other parameters are consistent. However, empirical formula can only predict the dynamic characteristics of the simple model. In order to realize virtual reality of the dynamic characteristics of the complex model more accurately, the BP neural network and finite element are adopted, respectively. Then, the computational results are also compared with those of the experimental to verify their reliabilities. In the future, the BP neural network and finite element method can be also used to realize virtual reality of the dynamic characteristics of the more complex model.

Crop, Tillage, and Landscape Effects on Near‐Surface Soil Quality Indices in Indiana

Core Ideas Soil quality scores were highest in perennial grass systems, followed by a soybean‐dominated rotation, followed by a corn‐based rotation. No‐till crop production had no higher soil quality score than chisel–disk tillage but the uncultivated perennial grass system scored higher than both. In this crop production‐dominated region, soil quality is driven by biological properties like soil C and β‐glucosidase activity and physical properties like bulk density and macroaggregate stability. Soil quality is a critical link between land management and water quality. We aimed to assess soil quality within the Cedar Creek Watershed, a pothole‐dominated subwatershed within the St. Joseph River watershed that drains into the Western Lake Erie Basin in northeastern Indiana. The Soil Management Assessment Framework (SMAF) with 10 soil quality indicators was used to assess inherent and dynamic soil and environmental characteristics across crop rotations, tillage practices, and landscape positions. Surface physical, chemical, and nutrient component indices were high, averaging 90, 93, and 98% of the optimum, respectively. Surface biology had the lowest component score, averaging 69% of the optimum. Crop rotation, tillage, and landscape position effects were assessed using ANOVA. Crop selection had a greater impact on soil quality than tillage, with perennial grass systems having higher values than corn (Zea mays L.) or soybean [Glycine max (L.) Merr.]. Furthermore, soybean rotations often scored higher than corn rotations. Uncultivated perennial grass systems had higher overall soil quality index (SQI) values and physical, chemical, and biological component values than no‐till or chisel–disk systems. Chisel–disk effects on overall and component SQI values were generally not significantly different from no‐till management except for a few physical indicators. Toe‐slopes had higher physical, biological, and overall SQI values than summit positions but toe‐slope values were not significantly different from those of mid‐slope positions. This work highlights the positive effects of perennial grass systems, the negative effects of corn‐based systems, and the neutral effects of tillage on soil quality.

A new rockfill dynamic characteristics analogy method using statistic relationship

Dynamic numerical analysis by the finite element method (FEM) is widely used for the seismic performance analysis of earth-rockfill dams. The dynamic characteristics of soil, which can be measured by dynamic tests, determine the results of the FEM analysis. However, due to their high costs and long duration, dynamic tests are not feasible for many small- to middle-scale earth-rockfill dams. As a result, the analogy method is employed. Because the traditional analogy method is highly dependent on personal experience, it lacks objective and accurate orientations. In this paper, a new method to analogize the dynamic characteristics of rockfill by prototype monitoring and statistic curves is developed. To examine its effectiveness, the dynamic parameters of a middle-scale concrete-face rockfill dam (CFRD) were analogized. The results of the dynamic FEM analysis agree well with the general rules which were shown in the earthquake response and the dynamic FEM analysis response of the same type of CFRD

Experimental study on the dynamic deformation characteristics of volcanic soil "Shirasu" on equivalent granular void ratio

Shirasu is a volcamic soil which is widely distributed in South Kyushu in Japan. It contains non plastic fines which was created by its fragment of coarse particles. In this study, a series of bender element tests on Shirasu was performed with varying its fines content. As a result, it was observed that the shear modulus of Shiarasu was decreased with increasing the fines content although void ratio decreased as fines content increased. However, it was found that there is a unique relationship between shear moduli of Shirasu and the equivalent granular void ratio, in which the proper contribution factor b for fines was assumed. Based on the findings in the study, an empirical formula to express the shear moduls of Shirasu with various fines content was developed as the function of the fines content, the equivalent granular void ratio and the effective confining stress.

Reliability Evaluation of Dynamic Characteristics of Clean Sand Soils Based on Soft Computing Methods

This study was conducted to estimate the dynamic characteristics of clean sand under low strains using fuzzy expert systems and neural network approximations. A series of resonant column tests were conducted on clean sand specimens to create a large database. The effects of various factors, such as effective pressure, saturation, void ratio and shear strain levels, were simulated using fuzzy expert systems and neural networks. The neuro-fuzzy inference method was employed to predict the initial shear modulus of clean sand samples as a substitute for time-consuming laboratory testing. Additionally, the maximum shear modulus results were compared with the existing empirical relationships. From these observations, it can be observed that certain relationships significantly underestimate the initial shear modulus. Simple empirical relationships to estimate the initial shear modulus were formulated. It is concluded that neuro-fuzzy-based models provide useful guidelines for the preliminary estimation of the dynamic shear modulus for clean sand soils.

The pore pressure model of cement soil under cyclic loading

The long-term settlement of soft soil under cyclic loading is significant, the reinforcement of cement soil can improve the dynamic characteristics of soft soil and reduce the settlement, so it has been widely applied in soft soil foundation treatment. Affected by the disturbance of metro shield tunnelling, the surrounding grout-strengthened soil possesses initial degree of consolidation and the variation pattern of pore pressure of cement soil is differentiated, which leads to differential settlement. Therefore, in this study, global digital system dynamic triaxial apparatus was used to simplify the dynamic loading of subway to biased sine wave, and the effect of initial degree of consolidation and cement ratio on the development pattern of pore pressure of cement soil was studied. Combining tests results and existing studies, pore pressure model incorporating the initial degree of consolidation, cement ratio and cyclic stress ratio was established. Results from this study showed that under cyclic load, the pore pressure increased dramatically at the early stage, then slowly and gradually became stable; the initial degree of consolidation affected the development of pore pressure to a certain extent: for specimens with low degree of consolidation, the pore pressure stabilised prior to others at high value; compared with remoulded soil, the increase in pore pressure of cement soil with a cement ratio of 15–20% was effectively reduced and so was the consolidation settlement after construction.

Model test on dynamic characteristics of invert and foundation soils of high-speed railway tunnel

A dynamic model test (CL = 4) at different velocities of train, namely different loading frequencies, is carried out to study the dynamic characteristics of a high-speed railway tunnel invert and its foundation soils. Not only are the accelerations, dynamic coefficients, dynamic stresses of the invert and foundation soils emphatically analyzed, their relationship with the velocity of the train are discussed in detail. Through laboratory testing, the attenuation of vibration propagating from up the rails is obtained and the calculation formula of the speed influence coefficient of the tunnel invert is preliminarily established. The depth of the foundation soils influenced by vibration is also determined in this study. It is shown that the responses of the tunnel invert and foundation soils to vibration are slightly increased with the velocity of the train; circumferential stresses in the bottom of the invert are tensile stresses and maximum stresses appear under the foot of the rails; the dynamic soil pressures of the foundation decrease quickly with the distance away from the tunnel invert and an exponential relationship exists between them.

Experimental and numerical evaluation of the effectiveness of a stiff wave barrier in the soil

This paper discusses the design, the installation, and the experimental and numerical evaluation of the effectiveness of a stiff wave barrier in the soil as a mitigation measure for railway induced vibrations. A full scale in situ experiment has been conducted at a site in El Realengo (Spain), where a barrier consisting of overlapping jet grout columns has been installed along a railway track. This barrier is stiff compared to the soil and has a depth of 7.5m, a width of 1m, and a length of 55m. Geophysical tests have been performed prior to the installation of the barrier for the determination of the dynamic soil characteristics. Extensive measurements have been carried out before and after installation of the barrier, including free field vibrations during train passages, transfer functions between the track and the free field, and the track receptance. Measurements have also been performed at a reference section adjacent to the test section in order to verify the effect of changing train, track, and soil conditions over time. The in situ measurements show that the barrier is very effective: during train passages, a reduction of vibration levels by 5dB is already obtained from 8Hz upwards, while a peak reduction of about 12dB is observed near 30Hz immediately behind the barrier. The performance decreases further away from the jet grouting wall, but remains significant. The experimental results are also compared to numerical simulations based on a coupled finite element–boundary element methodology. A reasonable agreement between experiments and predictions is found, largely confirming the initially predicted reduction. This in situ test hence serves as a ‘proof of concept׳, demonstrating that stiff wave barriers are capable of significantly reducing vibration levels, provided that they are properly designed.

Dynamic deformation of soft soil media: Experimental studies and mathematical modeling

A complex experimental-theoretical approach to studying the problem of high-rate strain of soft soil media is presented. This approach combines the following contemporary methods of dynamical tests: the modified Hopkinson-Kolsky method applied tomedium specimens contained in holders and the method of plane wave shock experiments. The following dynamic characteristics of sand soils are obtained: shock adiabatic curves, bulk compressibility curves, and shear resistance curves. The obtained experimental data are used to study the high-rate strain process in the system of a split pressure bar, and the constitutive relations of Grigoryan’s mathematical model of soft soil medium are verified by comparing the results of computational and natural test experiments of impact and penetration.

Threats to Sustainability of Soil Functions in Central and Southeast Europe

A diverse topography along with deforestation, changing climatic conditions, long-term human settlement, overuse of agricultural lands without sustainable planning, cultural difficulties in accepting conservative land management practices, and wrong political decisions have increased the vulnerability of many soils to degradation and resulted in a serious decline in their functional capacity. A progressive reduction in the capacity of soils to support plant productivity is not only a threat in the African continent and its large desert zone, but also in several parts of Central and Southeastern Europe (CASEE). The loss of soil functions throughout CASEE is mainly related to the human activities that have profound influence on soil dynamic characteristics. Improper management of soils has made them more vulnerable to degradation through water and wind erosion, organic matter depletion, salinity, acidification, crusting and sealing, and compaction. Unmitigated degradation has substantial implications for long term sustainability of the soils’ capability to support human communities and resist desertification. If sustainable agricultural and land management practices are not identified, well understood and implemented, the decline in soil quality will continue and probably accelerate. The lack of uniform criteria for the assessment and evaluation of soil quality in CASEE countries prevents scientific assessments to determine if existing management practices are leading to soil quality improvement, or if not, what management practices should be recommended to mitigate and reverse the loss of soil health.

Numerical Simulation of a Site Response Analysis with STRATA Software

The analysis of the ground foundation must take into consideration two main aspects: a simulation of the ground motion as close as possible to reality and the correlation of the ground motion with existing geological conditions. Thus, it can be distinguished two main functions of the soils: the function of a dynamic filter for the seismic movement that come from the source, and the function of a deformable spring for the buildings whose support is. In this paper, the behavior of a site was analyzed from the site response point of view, using different accelerograms of Romanian’s earthquake. These accelerograms were recorded during the 1977, 1986 and 1990 earthquakes. In order to perform equivalent linear site response analysis we use the STRATA software for a homogeneous soil layer with more than 10 meters depth. The soil type and the velocity layering were considered constant on the entire soil deposit. The analysis was done both on cohesive and cohesionless soils. The final results have been mapped in terms of soil dynamic characteristics, accelerograms and acceleration response spectrum, under different earthquake excitations. DOI: http://dx.doi.org/10.5755/j01.sace.9.4.7129

Experimental Study on the Dynamic Characteristic of Soft Soil under Cyclic Loads

To study the change law of the dynamic characteristics of soft soil, particularly the inadequate bearing capacity of highway and railway roadbeds induced by traffic loads, the soft soil in Yingkou area was taken as the research object. A series of dynamic strength and dynamic modulus tests were performed under different dynamic stress amplitude amplitudes, consolidation ratios, confining pressures, dynamic stress amplitudes, consolidation confining pressures, consolidation ratios, vibration frequencies, soft soil dynamic strains, dynamic strengths, dynamic backbone curves, dynamic moduli, and dynamic damping ratios. The results show that (1) Yingkou soft soil has a significant structural property. A strain turning point was found in the εd-N and dynamic curves. The deformation of soil increases rapidly when the strain is larger than this turning point. (2) Dynamic strength increases as consolidation confining pressures increase, but the influence of consolidation ratio and vibration frequencies on soft soil dynamic strength is not limited to an increase or decrease. (3) The dynamic modulus increases as consolidation confining pressure, consolidation ratio, and vibration frequencies increase, whereas dynamic damping ratio decreases with increasing pressure and ratio but increases with increasing vibrational frequency. The above results provide a theoretical basis for studying the insufficient bearing capacity of highway and rail roadbeds caused by long-term cyclic loads.

고화처리공법이 적용된 연약점토지반의 침하 및 지지력 개선에 관한 사례연구

본 연구에서는 광양 <TEX>${\bigcirc}{\bigcirc}$</TEX>산업단지 공사현장내의 도로 및 구조물 시공구간 중 연구대상 3구간을 선정하여 지반의 물리 역학적 특성을 분석하고 구조물 시공조건, 고화처리 단면조건에 따라 Midas-GTS를 통해 압밀해석과 지지력 산정을 수행하였다. 도로 및 구조물이 시공되는 연약점토지반의 침하 및 지지력 개선방안으로 고화처리공법 적용 시 지반의 안정성 개선효과와 고화처리단면에 따른 침하 및 지지력 개선효과를 분석하였다. 연약점토지반에 고화처리공법을 적용 시 침하 및 지지력 개선효과가 뛰어난 것으로 나타났으며 특히, 고화처리공법 적용 후 압밀침하량이 최소 53%에서 최대 82%까지 감소하여 압밀침하 억제효과가 우수한 것으로 나타났다. 고화처리 폭이 설치 구조물 폭의 2배 이상인 경우 고화처리 폭이 증가하여도 압밀침하 억제효과는 1~7%정도로 미소한 것으로 나타났다. 또한, 고화처리 폭 6m, 심도 1m이상 적용시 고화처리 전보다 허용지지력이 2.3~3.3배정도 크게 증가한 것으로 나타나 고화처리공법을 적용하면 지지력 증대효과가 매우 우수함을 알 수 있었다. In this study, the physical and dynamic characteristics of soil were analyzed by selecting 3 sections as research subjects among road and structure construction sections in the construction site of the Gwangyang <TEX>${\bigcirc}{\bigcirc}$</TEX> industry area, and conducted consolidation analysis and bearing capacity assessments through Midas-GTS according to the construction conditions of the structures and section conditions of reinforcement using stabilized soil. The effects of improving the settlement and bearing capacity according to the improved effects of the stability and sections of reinforcement using stabilized soil in applying the reinforcement method using stabilized soil were analyzed as a solution for improving the settlement and bearing capacity of soft clay for constructing roads and structures. The improvement effects of the settlement and bearing capacity were outstanding when the reinforcement method using stabilized soil to the soft clay was applied. After applying the reinforcement method using stabilized soil, the holdback effect of the consolidation settlement was excellent by decreasing the volume of the consolidation settlement from a minimum of 53% to a maximum of 82%. When the width of the reinforcement using stabilized soil was twice the width of the constructed structure, it was found that the holdback effect of the consolidation settlement ranged from 1% to 7% through the width of reinforcement using stabilized soil. In addition, when applying reinforcement more than 6m in width and 1m in depth using stabilized soil, it was found that the increase in the allowable bearing capacity was 2.3 to 3.3 times more than that before applying the reinforcement, which suggests that the increase in bearing capacity by applying the reinforcement method using stabilized soil was significant.

지반환경 변화에 따른 화강토의 동적특성

화강토는 우리나라에서 널리 분포하는 흙으로써 공기에 노출되거나 물과 접촉하면 강도특성이 쉽게 변화하는 흙으로 건설기술자가 가장 많이 당면하고 있는 지반재료이다. 특히, 이러한 재료는 계절적 환경변화를 거치게 되면서 토류구조물의 주 구성요소인 배면지반은 습윤-건조, 동결-융해 및 자연 또는 인공적인 풍화과정을 거치게 된다. 따라서 본 연구는 이러한 지반환경변화 후 화강토의 동적거동 특성에 미치는 지반환경 및 풍화조건이 무엇인지를 공진주 실험을 통해 연구하였다. 본 연구결과 화강토의 동적특성에 가장 큰 영향 미치고 있는 지반환경 조건은 습윤-건조 풍화조건이며, 다음으로 인공풍화 조건이 초기에는 큰 영향을 미치다가 동결-융해 사이클 횟수가 증가할수록 동결-융해 조건이 더 큰 영향을 미치는 것으로 나타났다. Decomposed granite soil is likely to lose its strength when exposed to air or water. Such a geomaterial is weathered by wetting-drying or freezing-melting. In this study, resonant column tests were conducted to figure out the dynamic characteristics of granite soil that has affected by environmental changes like weathering condition. The results show that wetting-drying weathering condition is the most affective parameter on the dynamic characteristics of granite soil. In the meantime, artificial weathering conditions such as freezing-melting has less affection at first and getting increase as the process repeats constantly.

Testing and Analysis on Dynamic Rheologic Characteristics of Soft Soil under Different Breadth Conditions of Dynamic Loading

The practical investigating and theoretic analysis Indicates that the rheologic action of the soft rock-soil could be accelerated by the dynamic loading, which induces more geotechnical engineering accidents and geologic disasters. The samples of marine deposit soft soil are collected in xiamen, and the dynamic stress-strain, the rheologic strain-time etc rheologic characteristics curves under the different breadth of dynamic loading of sinusoidal variation are tested using dynamic-triaxial device. The rheologic characteristics, rheologic rate and rheologic acceleration varietal process of four different breadths are analyzed. The research results indicate that all the samples are the same varietal process from decelerate rheology, relatively stable rheology to accelerate rheology stage. The dynamic strain slow growth and the rheologic process is relatively stable when the breadth of dynamic loading is low stress ranges of 10~20kPa.When the breadth of dynamic loading exceed 40kPa, the dynamic strain rapid growth and the rheologic is accelerate process till the samples destroy. The research results have academic and actual signification for us to open out the dynamic rheologic mechanics characteristic, explore the accelerating rheologic laws and the rheologic destabilizing dynamic condition of soft rock-soil under dynamic loading.

Seismic Response Characteristics of Subway Station Structure

The dynamic Davidenkov model is used to model dynamic characteristics of soils, and plastic-damage model is used to model dynamic characteristics of station structure concrete. So that, considering the influence of soil-station structure interaction for 2D finite element analysis, the dynamic interaction of soil-station structure is modeled. The damage characteristics and energy response of station structure under seismic motion is analyzed. The result shows that damping energy and hysteretic energy are monotone increasing under ground motion, and the seismic characteristic has significant effect on the energy response of subway station structure. Furthermore, concentration effect of hysteretic energy of subway station structure is measured by hysteretic energy density. It is found that the hysteretic energy is the most centralized in the column, so the dynamic response of the columns is the maximum. Furthermore, the nonlinear damage evolution law of station structure is analyzed. The law of local and global damage index is consistent essentially, and the damage index is increased by the effect of accumulative deformation.

Study of Soil Liquefaction Analysis Based on the P-Z Model

Dynamic constitutive models and liquefaction characteristics of soil are critical in the seismic stability analysis on embankment dams. The P-Z constitutive model, which is a kind of the multi-mechanism plastic model based on generalized plasticity, is mainly introduced in this paper. Considering soil as two-phase media, based on the Biot fluctuation theory and the P-Z model, the dynamic analysis formulation of two-phase media is established, and the criterion of soil liquefaction is proposed through investigations, where the generation and dissipation process of soil pore pressure and the variations of effective stress are taken into account. Furthermore, the interface conditions between two-phase media and the other types of medium are derived and the examples of verification are presented.

The Status Analysis of Constitutive Relation and Parameters of Soil Dynamics

This article describes the research progress and the development situation of soil dynamics. The soil dynamic constitutive model, dynamic test methods and research status of dynamic parameters are mainly discussed. Finally, some existing problems on the study of soil dynamic characteristics are proposed.

Contribution of soil-structure interaction to seismic response of buildings

Buildings are susceptible to soil structure interaction effects due to the induced changes in the dynamic characteristics of soil during seismic excitation. Because of this detrimental effect, this paper aims at clarifying the soil structure interaction effect on the seismic response of buildings under strong ground motions to provide damage control and enhance the safety level of such buildings. An iterative dynamic analysis was performed using the SAP2000 program to carry out three dimensional time history analysis of nonlinear soil-foundation-building models under a great earthquake ground motion, and the results show that incorporating the soil structure interaction could have a detrimental effect on the building performance and overestimates the top displacements response. On the contrary flexible bases of buildings have a noticeable effect on the structural behavior of buildings by providing pronounced reduction in the internal forces of superstructure response compared to the fixed base buildings.