Elastic Modulus Of Soil Research Articles

Bearing Behavior Study of Rammed Cement-Soil Pile Compounded Foundation in Collapsible Loess

The rammed cement-soil pile compounded foundation is widely used in collapsible loess of northwest China. There are many factors influencing the bearing capacity of compounded foundation. The calculation result with empirical formula are usually not accurate. The influence factors on bearing capacity of compounded foundation are analyzed with finite element method based on the static load results. The result show that pile body elastic modulus has little effect on the bearing capacity of compounded foundation. This is quite different from bearing behavior of single pile. However, the soil parameters, such as soil elastic modulus, soil internal friction angle and soil cohesion have significant impact on compounded foundation bearing capacity.

Stochastic dynamic stiffness of a surface footing for offshore wind turbines: Implementing a subset simulation method to estimate rare events

The purpose of this study, which concerns the stochastic dynamic stiffness of foundations for large offshore wind turbines, is to quantify uncertainties related to the first natural frequency of a turbine supported by a surface footing and to estimate the low event probabilities. Herein, a simple model of a wind turbine structure with equivalent coupled springs at the base is calibrated with the mean soil property values. A semianalytical solution, based on the Green׳s function for a layered half-space is utilized for estimation of foundation responses. Soil elastic modulus and layer depth are considered as random variables with lognormal distributions. The uncertainties are quantified, and the estimation of rare events of the first natural frequency is discussed through an advanced reliability approach based on subset simulation. This analysis represents a first step in the estimation of the safety with respect to the failure of a turbine in the fatigue limit state.

Numerical Simulation of Squeezed Branch and Plate Pile Subjected to Vertical and Lateral Loads

Based on the theoretical analysis results, the bearing behavior of squeezed and branch pile under vertical load and lateral load was analyzed in this paper. The mean works include the influence of vertical load on the pile lateral bearing capacity and influence of the lateral load on the vertical load bearing capacity. The factors influence the bearing capacity of pile such as elastic modulus of soil around and under pile bottom, pile length, plate position are also analyzed.

Numerical study of ground vibration due to impact pile driving

Ground vibration due to pile driving is a long-lasting concern associated with the foundation construction industry. It is of great importance to estimate the level of vibration prior to the beginning of pile driving, to avoid structural damage, or disturbance of building occupants. In this study, an axisymmetric finite-element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code Abaqus, to simulate full penetration of the pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been verified by comparing the computed particle velocities with those measured in the field. The results indicate that the peak particle velocity at the ground surface does not occur when the pile toe is on the ground surface; as the pile penetrates into the ground, the particle velocity reaches a maximum value at a critical depth of penetration. Some sensitivity analyses have been performed to evaluate the effect of soil, pile and hammer properties on the level of vibrations. The results show that increase in pile diameter, hammer impact force, soil–pile friction and reduction in soil elastic modulus can increase the peak particle velocity.

Settlement Analysis for Embedded Foundation Resting on Non-Homogeneous Subgrade

Elastic modulus of soil increases continuously with depth because of the overburden pressure. By combining the modified Mohr-Coulomb elastic-plastic constitutive model with this type of nonhomogeneous subgrade and considering factors of embedment depth of foundation, friction coefficients between the foundation bottom face and soil, the nonhomogeneity and strength of subgrade soil are analyzed by FEM method. It is shown that the settlement laws of the magnitude and the distribution range of the subgrade are different to other models using in literatures ordinarily

Method for Getting the Soil Elastic Modulus in the Finite Element Analysis of the Deep Foundation Excavation in Tianjin

The finite element method has been used widely in foundation pit engineering to simulate the deep foundation excavation, but it is troublesome and time-consuming to get the important calculation parameter of the soil elastic modulus. So a method based on the comon soil parameters is proposed to get the soil elastic modulus. And a real foundation excavation was simulated using the finite element software ABAQUS and the soil elastic modulus got according to the proposed method. The three-dimensional finite element analysis results were compared to the field data, and both results were close to each other.

Numerical Analysis of Tunneling Influence on Settlement of Existing Pile Foundations Based on Orthogonal Design

Because of the Limited urban space and the development of transport, underground space development, especially the metro construction, is vigorously developed in many cities. Subway passing through the existing building inevitably may cause the settlement and deformation of the buildings and their foundations. Therefore, research on the influence of tunneling on existing buildings has important significance. In order to study the influence of tunneling on settlement of existing pile foundations, soil elastic modulus, cohesion, friction angle, tunneling sizes, distance between tunnel opening boundaries and existing pile foundation etc. are discussed as analysis factors in this paper. The calculation schemes are designed based on orthogonal design, and then the influence of tunneling on existing buildings is researched according to the numerical calculation model which is established by the finite element software. Finally, the sensitivity of pile foundation settlement to various factors is analyzed according to the results of simulation analysis. we can draw the conclusions: the influence of tunneling on settlement of existing pile foundation is positively correlated with tunneling sizes, and is negatively correlated with soil parameters and distance between tunnel opening boundaries and existing pile foundations; The settlement of pile foundations can be effectively controlled by application of composite anchor isolation piles around the existing buildings piles, but with the increase of soil parameters and distance between tunnel opening boundaries and existing pile foundations, the strengthening effects are decreased; soil elastic modulus and excavation sizes are the key impact-factors of pile settlement within the distance of 5m between tunneling boundaries and existing pile foundations, which have extremely remarkable effect on the subsidence of pile foundations.

Analysis of Seismic Factors to Tunnels in the Earthquake

Underground structures have mechanical characteristics and seismic responses very different from common structures on the ground in the earthquake due to the constraints of the surrounding soil. Tunnel destruction has occurred many times in domestic and international earthquake. In order to study seismic factors and failure mechanism of tunnels in the earthquake, numerical simulation of the seismic responses of the circular shield tunnel is carried on. Harmonic P-waves and S-waves are entered to make the tunnel vibrate and deform. Viscous-spring artificial boundary condition is applied in the numerical simulation to consider the semi-infinity of soil. The elastic modulus of soil, the frequency of harmonic waves and the depth of the tunnel are regarded as the main factors. The seismic responses such as stress and relative displacement are analyzed in different parameters to get the failure mechanism of circular tunnel.

Numerical modelling of short pile behaviour subjected to lateral load

The behaviour of laterally loaded short rigid piles founded in sandy soil has been investigated numerically by performing a series of three-dimensional non-linear finite element analyses. The parameters investigated are relative density and elasticity modulus of sandy soil, load eccentricity, pile geometry and geometric configurations such as pile cross-section, embedment ratio and pile diameter. The results of the existing design methods used for predicting the lateral load capacity of short rigid piles were compared with the results of the three-dimensional non-linear finite element analyses. The results proved that the parameters investigated had considerable effect on the behaviour of rigid piles subjected to lateral loads. It was also shown that the value of the ultimate lateral load capacity could be significantly different depending on the conventional methods used.

Predicting surface vibration from underground railways through inhomogeneous soil

Noise and vibration from underground railways is a major source of disturbance to inhabitants near subways. To help designers meet noise and vibration limits, numerical models are used to understand vibration propagation from these underground railways. However, the models commonly assume the ground is homogeneous and neglect to include local variability in the soil properties. Such simplifying assumptions add a level of uncertainty to the predictions which is not well understood. The goal of the current paper is to quantify the effect of soil inhomogeneity on surface vibration. The thin-layer method (TLM) is suggested as an efficient and accurate means of simulating vibration from underground railways in arbitrarily layered half-spaces. Stochastic variability of the soil's elastic modulus is introduced using a K–L expansion; the modulus is assumed to have a log-normal distribution and a modified exponential covariance kernel. The effect of horizontal soil variability is investigated by comparing the stochastic results for soils varied only in the vertical direction to soils with 2D variability. Results suggest that local soil inhomogeneity can significantly affect surface velocity predictions; 90 percent confidence intervals showing 8dB averages and peak values up to 12dB are computed. This is a significant source of uncertainty and should be considered when using predictions from models assuming homogeneous soil properties. Furthermore, the effect of horizontal variability of the elastic modulus on the confidence interval appears to be negligible. This suggests that only vertical variation needs to be taken into account when modelling ground vibration from underground railways.

P-delta effects on earthquake response of structures with foundation uplift

The earthquake responses of structures are usually analyzed under the assumption that the foundation is firmly bonded to the soil (fixed at their base). Such analyses often predict a base overturning moment that exceeds the available overturning resistance due to gravity loads, which implies that a portion of the foundation mat or some of the individual column footings, as the case may be, would intermittently uplift during the earthquake. In addition, p-delta phenomena are another valuable parameter that influence the response of structure with foundation uplift. Therefore it is a vital subject to investigate the influence of uplift on earthquake response of structures with including the p-delta effects. In the current paper, the investigation has been performed using finite element method with considering nonlinear material behavior. The computer program used already incorporates foundation uplift in a more realistic approach than structural models available in literature. The response of structures was compared in four cases: 1—with foundation uplift, 2—without foundation uplift, 3—with including the p-delta effects and 4—without including the p-delta effects. Some additional parametric studies have been conducted such as slender of structure, elastic modulus of soil and bi-directional input ground motion. These studies show the importance of uplift foundation on the seismic behavior of structures and the beneficial effects of foundation uplift in computing the earthquake response of structures are demonstrated. In addition, p-delta effects are the main reason to resonate the differences between the four cases.

The Influence to Modal Parameters of Retaining Wall by the Elastic Modulus of Soil

The characteristic of soil is one of the main factors that influence the modal parameters of retaining wall. This paper analyzes the influence to modal parameters of retaining wall by the elastic modulus of soil. Due to the complexity of the interaction of soil and retaining wall and based on the three-dimensional numerical test, dynamic response signals of retaining wall are obtained, processing of which and identification of modal parameters lead to the modal parameters of retaining wall. Lastly, vibration characteristic, frequency characteristic and the relationship of frequency and elastic modulus are also obtained.Therefore, the real elastic modulus of soil is gained by response signals in practical projects, and the degree of soil compaction can be pre-judged.

Simulation and Analysis for Laterally Loaded Pile in Clay

It was presented for the results of 3D finite difference analysis on the behavior of single pile in clay. Firstly, it was discussed to the effect of model’s mesh fineness and soil parameters on pile response. And it was founded that the mesh size less than 0.2d (diameter of pile) was reasonable. In additions, when the soil was soft or the E(soil elastic modulus) was small, the effect E of on lateral capacity of pile was larger than the soil was stiff clay with soil elastic modulus increasing. Lastly, the results of the numerical simulation carried out in this study were compared with a published field lateral loading tests, a good correlation between the field test and the numerical simulation was obtained based on reasonable mesh size and material parameters.

Strategy of Transformation on Existing Residential Buildings for Energy Saving in the North of China

A general numerical simulation method is presented for the analysis of the dynamic interaction problem between a large-span concrete culvert, discretized by a plane strain finite element model (FEM), and a dynamic system of vehicle traversing at various speeds. The vehicle is represented as a mass-spring-damper FEM system with seven degrees of freedom. The time-variable coupled dynamic system is solved by a step-by-step solution technique using Newmark’s integration scheme. The backfill soil elastic modulus is modeled as varying linearly with depth below the ground surface. Several numerical examples are investigated by modifying different parameters such as backfill height and road surface stiffness, respectively. The dynamic displacement response for the mid-span point of the concrete culverts is analyzed, as well as the displacement impact factor. The research results demonstrate that the impact factor changes with the vehicle speed and strongly depends on the road surface roughness conditions.

Vibration Analysis of a Moving Truck on a Long Span RC Culvert

A general numerical simulation method is presented for the analysis of the dynamic interaction problem between a large-span concrete culvert, discretized by a plane strain finite element model (FEM), and a dynamic system of vehicle traversing at various speeds. The vehicle is represented as a mass-spring-damper FEM system with seven degrees of freedom. The time-variable coupled dynamic system is solved by a step-by-step solution technique using Newmark’s integration scheme. The backfill soil elastic modulus is modeled as varying linearly with depth below the ground surface. Several numerical examples are investigated by modifying different parameters such as backfill height and road surface stiffness, respectively. The dynamic displacement response for the mid-span point of the concrete culverts is analyzed, as well as the displacement impact factor. The research results demonstrate that the impact factor changes with the vehicle speed and strongly depends on the road surface roughness conditions.

Non-Linear Finite Element Analysis of Squeezed Branch Pile

In this paper, in order to analyze the capability of squeezed branch pile under different work condition and the cooperation mechanism between the pile and soil, non-liner numerical simulation was carried out using ANSYS. In the finite element model, the elastic-perfectly plastic Drucker-Prager material was assumed for soil. Contact interface elements were placed between the pile and soil. It showed that the squeezed branches took lots of the load, and the ratio it took was related to the load and the elastic modulus of soil; the plastic section of the soil was run-through from bottom to the top; the horizontal displacement of the top soil was moved to the pile, but the horizontal displacement of the soil of the bottom was moved away from the pile; the squeezed branch will break away from the soil above the squeezed branch when the load was at a certain value.

Three-Dimensional Large Deformation Finite-Element Analysis of Plate Anchors in Uniform Clay

Three-dimensional large deformation finite-element (FE) analyses were performed to investigate plate anchor capacity during vertical pullout. The remeshing and interpolation technique with small strain approach was expanded from two-dimensional to three-dimensional conditions and coupled with the FE software, ABAQUS. A modified recovery of equilibrium in patches technique was developed to map stresses after each remeshing. Continuous pullout of rectangular plate anchors was simulated and the large deformation results for strip, circular, and rectangular anchors were compared with model test data, small strain FE results, and plastic limit solutions. Interface conditions of no breakaway (bonded) and immediate breakaway (no tension) were considered at the anchor base. The effects of anchor roughness, aspect ratio, soil properties, and soil overburden pressure were investigated. It was found that the anchor roughness had minimal effect on anchor performance. For square and circular deep anchors under immediate breakaway conditions, the maximum uplift capacity increased with soil elastic modulus, which suggests that lower bound limit analysis and small strain FE analysis may overestimate the capacity. The soil beneath the anchor base separates from the anchor at a certain embedment depth near the mudline, once tensile stresses were generated. The ratio of separation depth to anchor width was found to increase linearly with the ratio of soil undrained shear strength to the product of soil effective unit weight and anchor width and was independent of the initial anchor embedment depth.

Geostatistical modelling of spatial and depth variability of SPT data for Bangalore

The purpose of this study is to develop a geostatistical model to evaluate the spatial and depth variability of Standard Penetration Test (SPT) data from Bangalore, India. The database consists of 766 boreholes spread over a 220 km2 area, with several SPT values (N) in each of them. The geostatistical analysis is done for N corrected (N corrected) values. The N corrected value has been corrected for different parameters such as overburden stress, size of the bore hole, type of sampler, hammer energy and length of the connecting rod. The knowledge of the semivariogram of the SPT data is used with kriging theory to estimate the values at points in the subsurface of Bangalore where field measurements are not available. The model is used to compute the variance of estimated data. The model predicts reasonably well the SPT data. The geostatistical model provides valuable results that can be used for seismic hazard analysis, site response and liquefaction studies for the development of microzonation maps. The predicted N values from the developed model can also be used to estimate the subsurface information, allowable bearing pressure of soils and elastic modulus of soils.

Three-Dimensional Probabilistic Foundation Settlement

By modeling soil as a three-dimensional spatially random medium, the reliability of shallow foundations against serviceability limit state failure, in the form of excessive settlement and/or differential settlement, can be estimated. The soil’s elastic modulus, E , is represented as a lognormally distributed random field with an isotropic correlation structure. The settlements of individual and pairs of square footings placed on the surface of the soil are computed using the finite element method. A probabilistic model for total and differential settlement is presented and compared to results obtained using Monte Carlo simulation. The distributions of total and differential settlement are found to be closely predicted using the distributions of geometric averages of the underlying soil elastic modulus field.

Container structures on a Vlasov foundation with variable soil characteristics

In this study container structures such as cylindrical vessels which have a flat or shallow spherical shell bottom on a Vlasov foundation with variable soil characteristics, are investigated. The variation of the soil's elastic modulus is assumed exponential along the depth of soil layer. Interaction between superstructure, foundation and soil is taken into account. The loading is considered as axisymmetric relative to the center of the bottom. The solution is achieved using the flexibility method, in which the wall is represented by distributed loads and moments along the circumference of the bottom. Some parametrical results are obtained for various soil layer depth-to-bottom radius ratios and comparisons are made between exponential and the other variations of the soil's elastic modulus.