Horizontal Displacement Of Soil Research Articles

Design of Conical Foundations with Increased Bearing Capacity in Areas of Undermined Soils

This article discusses the foundations of a conical shape directed with their apex downwards to increase the cross-sectional area and, accordingly, the bearing capacity during settlement and under the influence of horizontal tensile strains in undermined areas. To simulate the deformability of undermined and seismically exposed foundations, a three-dimensional expandable box was manufactured and assembled. Models of a conical foundation with an aperture angle of the cones at 90° and 80° were buried into the soil at 0.75 of its height, in order to provide a safety margin for further loading due to an increase in the bearing area when the cone is immersed deeper into the ground. Laboratory and field tests were performed on the vertical loading of single cones before and after horizontal soil displacement. Numerical modeling of the interaction between soil and foundation was carried out for conical foundation models that were considered for laboratory and field testing using the Plaxis 2D (Version 8.2) program. To compare the bearing capacity, isolated shallow foundations with a diameter equal to the cross section of the conical foundation at the intersection with the ground surface were tested. The isolated shallow foundations lost their bearing capacity after 0.15 kN in laboratory tests and after 75 kN in the field tests, while the ultimate bearing capacity of conical foundations with the similar cross section at the soil surface was not achieved, even after 0.2 kN during laboratory tests with horizontal soil displacement and at a load of 100 kN in field tests.

A Study on the Potential of Sand Liquefaction Hazard at Chukai Sentral, Terengganu Using Plaxis 2D

An earthquake is classified as a natural disaster of mother nature. Sometimes, it cannot be predicted when it will occur and difficult to estimate the striking force values and the period of incident. The effect of the earthquake may catastrophic if the magnitude is more than 6 Richter. It had been proved by previous event, an earthquake could cause a huge impact towards the soil condition especially when the saturated soil is soft or loose since the propagation of shear wave and compression could induced the soil liquefaction and gave an effect towards excess pore pressure and effective stress of the soil that may affect the stability of infrastructure such as dam, embankment, and bridge. This study was conducted to analyse the horizontal displacement of soil due to earthquake and to evaluate the possibility of liquefaction at Chukai Sentral, Kemaman, Terengganu, Malaysia. The study was conducted using Plaxis-2D software based on Mohr-Coulomb soil model at magnitude of 5.4 Richter. The Mohr-Coulomb model was selected as its failure occurs when the shear stress acting on the soil reaches a critical value and the shear strength is related to the effective stress acting on it. The analysis was concentrated on the mesh deformation and horizontal displacement. The result shows the mesh deformation and horizontal displacement obtained in the boreholes not more than 6 mm. It is considered as a small deformation and will not trigger to the potential of liquefaction to that area. It can be concluded that the earthquake magnitude of 5.4 Richter is unable to disturb the natural resistance of the soil and structure due to their stiff layer proportion.

Simplified Continuum Model for Laterally Loaded Rigid Piles and Poles Considering Vertical and Horizontal Soil Displacements

Simplified Continuum Model for Laterally Loaded Rigid Piles and Poles Considering Vertical and Horizontal Soil Displacements

Field study on installation effects of pre-bored grouted planted pile in deep clayey soil

This paper presents the results of field tests performed to investigate the installation effects of pre-bored grouted planted (PGP) pile in deep clayey soil. The variation of horizontal soil displacements, excess pore water pressures and lateral soil pressures was measured in the PGP pile installation process. The test results show that the drilling and grouting process induced large horizontal soil displacements in the soil within a radial distance of 2 d ( d is pile diameter), and the maximum horizontal soil displacements induced by the drilling and grouting process were smaller than 15.9 mm when the radial distance reached 4–5 d. Moreover, the horizontal soil displacements decreased along the soil layer depth, as the superficial soil layers were of small deformation modulus and lateral soil pressure. The drilling process brought large excess pore water pressures in the soil when the radial distance was less than 3 d, and the excess pore water pressures induced by the drilling stage were all less than 55 kPa when the radial distance reached 4–6 d. The drilling process also induced some lateral soil pressure increases in the soil within a radial distance of 3 d, while the measured maximum lateral soil pressure increases were smaller than 10.9 kPa when the radial distance increased to 4 d. On the whole, the excess pore water pressures and lateral soil pressure increases induced by the installation of PGP pile were much smaller than that induced by the installation of driven PHC pile. Moreover, the horizontal soil displacements, excess pore water pressures and lateral soil pressure increases induced by the installation of PGP pile all recovered rapidly after the installation of pile, as the cemented soil in the pile hole was in liquid state after the drilling and grouting stage.

Calculation and Analysis of Soil Deformation Induced by Lubrication Mud Pressure During Pipe Jacking Construction

As a key step to decide the pipe jacking construction success or failure, the control of lubrication mud performance and parameters directly affects the magnitude of jacking force and deformation of surrounding soil. In order to establish soil deformation model induced by lubrication mud pressure during pipe jacking construction, based on the mechanism analysis of lubrication mud and surrounding soil, using equivalent model of cavity in the semi-infinite elastomer on internal pressure solves the deformation of soil under the effect of mud pressure, referencing image method and stress function method, which deduces the analytical formula of stress and deformation of surrounding soils caused by mud pressure. At the same time, the pattern of soil deformation is analyzed and obtained, the overlying soil vertical displacement increasing with pipes buried depth increasing and the horizontal displacement of soil on both sides pipes increasing with the depth increasing at first then decreasing.

Influence analysis of overlying soil layer to seismic behavior of inclined liquefiable soil and pile interaction system

The statistical data of earthquake hazard indicate that the liquefaction and large lateral flow deformation of ground is one of the main reasons of pile foundation failure. It is significant to focus on the seismic dynamic behavior of pile foundation in inclined liquefiable soil. Based on the Opensees finite element platform, an integrated finite numerical model of inclined liquefiable soil-pile group-structure interaction is established in this study, according to the shaking table model test of inclined liquefiable soil. The nonlinearity of pile-soil contact and the shear localization of soil layer are considered in the numerical simulation. The comparison of the numerical simulation result with the shaking table test results are verified. In order to discuss the influence of different overlying soil layer on the seismic behavior of soil and pile system, a typical inclined liquefiable soil-pile group-structure interaction finite element model is established by the proposed numerical simulation method. The results show that the overlying soil layer has an obvious influence on the seismic dynamic behavior of the pore pressure, the horizontal displacement of soil and pile. The increase of the thickness of overlying soil can reduce the liquefaction degree of sand and improve the mechanical performance of pile foundation.

Theoretical analysis on horizontal rectification of tunnel near deep foundation pit by grouting

In a city with crowded underground space, the excavation of deep foundation pit leads to excessive displacement of adjacent subways and tunnels, which poses serious threats to the safety of existing tunnel structures. At present, theoretical analysis of the horizontal displacement rectification of tunnel by compaction grouting near a deep foundation pit is rarely reported. In this study, the analytical solution is derived based on the source-source theory and cavity expansion theory for grouting in a quarter-infinite space with a vertical rigid boundary (i.e. a rigid retaining structure). The horizontal displacement of tunnel can be determined onthebasisof the Pasternak foundation beam theory. Then the calculated horizontal displacement of tunnel is validated against the measured results obtained from a tunnel rectification test based on grouting in Tianjin and a rectification engineering in Shenzhen. Based on the theoretical solution proposed in this study, the grouting parameters and modes are optimized to reach a high-efficient rectification. For the single-opening grouting, with the increase of horizontal distance from the grouting tube, the horizontal displacement of soil gets lower and becomes negligible (less than 0.5 mm) at 12 m away from the tube. For the multi-row grouting, the depth of the end of the grouting tube should be reduced for high-efficient rectification.

Prediction method of soil horizontal displacement caused by non-uniform distribution of disturbance force in shield construction

Based on the Mindlin solution, this paper considers the influence of factors such as the non-uniform distribution of additional thrust of the cutter head influenced by lateral earth pressure in shield excavation, the non-uniform distribution of friction of shield shell influenced by soil softening and slurry spreading, and the non-uniform distribution of grouting pressure influenced by slurry spreading on the horizontal displacement of soil. The existing prediction formula is revised and verified by engineering examples. It is found that: affected by the shield construction disturbance force, the horizontal displacement behind the excavation surface is larger than that in front of the excavation surface, and the peak value of the horizontal displacement appears around the tunnel axis; through the verification of engineering case, when calculating the horizontal displacement in front of the excavation surface, the calculation results of both the modified formula and the original formula are in good agreement with the measured values, which can reflect the change trend of the measured horizontal displacement; when calculating the horizontal displacement behind the excavation surface, the calculation result of the existing formula has a great error due to the assumption of uniform distribution of disturbance force, which is different from the law of the measured result; the calculation result of the modified prediction formula is obviously in better agreement with the measured deformation value, and the error is smaller, which is more in line with the engineering reality.

Analysis of influence of deformation modes of retaining structures on deformation of a side shield tunnel

In the process of foundation pit excavation, different retaining structures and support stiffness may lead to different deformation modes of retaining structures. The soil displacement cause by the deformation of the retaining structure is calculated by the virtual image technique. Meanwhile, the collaborative deformation model for rotation and dislocation is introduced to analyze the tunnel longitudinal deformation caused by different deformation modes as well as the tunnel maximum displacement equivalent field, and two case verifications are carried out. The study shows that there is a large difference in the size and distribution law of the soil displacement field caused by different enclosure structure deformation modes. The horizontal displacement of soil caused by the cantilever type always shows a "cantilever type" curve with increasing horizontal distance from the enclosure structure, while the composite type, inner convex type and kicker type develop from the "bow" to the "cantilever type" curve. The vertical displacement field of the soil is in the shape of a "spoon" and the soil exhibits a certain bulge deformation below the critical depth. The critical depths of the composite type and inner convex type are similar, while the kick type is the largest and the cantilever type is the smallest. The influence area of the maximum horizontal displacement of the tunnel outside the pit of the inner convex type and the composite type is basically the same. The influence area of the cantilever mode is the smallest, while the influence depth of the kick-in mode is higher than that of the other three deformation modes.

Performance of a 56 m deep circular excavation supported by diaphragm and cut-off double-wall system in Shanghai soft ground

The performance of a 56 m deep circular excavation supported by a double-wall system, consisting of an inner circular diaphragm wall and an outer rectangular cut-off wall, in Shanghai soft ground is studied in this paper. The surveyed data (e.g., lateral wall deflections ( δ h), horizontal displacement of soil ( δ s), ground surface settlement ( δ v), soil rebound ( δ v+), earth pressure ( P), pore water pressure ( Pw), and soil stress path) are systematically investigated. The results show that the maximum lateral wall deflections are 0.002% ∼ 0.03% of the excavation depth ( H e). The maximum ground surface settlement ( δ v m) is generally larger than δ h m, which is located at 0.4 ∼ 0.6 H e. Moreover, an innovative formula is proposed to estimate the ground settlement. It is able to distinguish various characteristics of surface settlement in different zones of the settlement profile. The ground surface settlements are mainly induced by surcharge loading and continuous excavation, and they are related to the change in confined water level. The lateral earth and pore water pressures in the active zone are relatively insensitive to the excavation, while the correlation becomes obvious in the passive zone. The findings from this study can be helpful to the design of other similar deep excavations in soft clay.

Seismic Response of a Liquefiable Site-Underground Structure System

To study the dynamic response of a saturated sand-underground structure system subjected to earthquakes, a series of shaking table tests with a geometric scale ratio of 1/30 were conducted. Based on the experimental acceleration records of testing soil deposits, the relationship between dynamic shear stress and horizontal soil displacement was analyzed by the 1D shear beam inverse calculation method. Meanwhile, the development law of the equivalent dynamic horizontal subgrade reaction coefficient and the dynamic strain of the sidewall in the underground structure has also been discussed. The testing results indicate that the dynamic shear stress of the soil deposit under the bottom plate of the underground structure is larger than that of the soils surrounding the sidewall and above the roof plate; in addition, the soil displacement tends to decrease with the buried depth. The dynamic shear stress–displacement hysteretic loop of the soil deposits tends to be plump as the input amplitude increases. The spectral characteristics of ground motions obviously influence both the dynamic shear stress–displacement hysteretic curve and the excess pore water pressure ratio of saturated sand soil, especially under medium and strong excitations. The equivalent dynamic horizontal subgrade reaction coefficient decreases with the increase of soil depth, and the difference between the coefficient above and underneath the underground structure model can reach 7.589 MN/m3. On the contrary, the equivalent dynamic horizontal subgrade reaction coefficient decreases with the increase of the input amplitude of ground motions, and the maximum reduction ratios of the coefficient are 74.4%, 66.7%, and 47.3%, corresponding to the El-Centro, Kobe, and Wolong ground motions, respectively. The soil liquefaction has a certain effect on the equivalent dynamic horizontal subgrade reaction coefficient. In general, the dynamic strain at the top of the sidewall in the underground structure is higher than that at the bottom of the sidewall, which illustrates that the deformation of underground structures is in good agreement with the seismic deformation mode of soil deposits.

Case analysis of sudden cracking in buildings near a landfill pit in China

The causes of cracks in a six-storey building are studied. Based on analyses of crack morphology, settlement observation and geological survey, it is determined that the landfill pit and uneven settlement are the main cause of cracks. The 20 July Zhengzhou rainstorm in China caused a sharp rise in groundwater level, so that the uneven settlement of the office building near the landfill pit intensified, and then, wall cracking followed. The interaction between buildings and landfill pits under different water levels is studied by three-dimensional numerical simulation. As the water level rises, the horizontal displacement of soil in the landfill pit increases, and the lateral constraint of landfill soil to foundation soil decreases. The result is that the settlement of the column foundation near the landfill pits increases and the differential settlement intensifies. Based on the analysis results, the further development of differential settlement and cracks are evaluated and treatment suggestions are given.

Theoretical method for additional horizontal stress of isolation piles due to adjacent loading

AbstractIsolation piles are widely used to increase the horizontal resistance of high‐speed railway under adjacent loading in soft soils. This study proposes a theoretical model for horizontal additional stress of pile‐reinforced area subjected to adjacent loading. The isolation piles and the soil between piles in the reinforcement area are equivalent to a uniform medium in the proposed model. The Heaviside function is introduced to avoid the partition solution problem of pile‐reinforced area and the foundation soils. A combined method with the inverse Fourier transform, Gauss integral, Lagrange quadratic interpolation, and Simpson quadrature formula is employed in the calculation process. The theoretical model is validated by the finite element method. According to the calculated results, the distribution of horizontal additional stress is obtained. The horizontal soil displacements at the location of the railway increases in the depth range of 0–2.5 m and then gradually decreases. The proposed model with engineering significance is available for preliminary design of isolation piles.

Dynamic pile-head stiffness of laterally loaded end-bearing pile in linear viscoelastic soil − A comparative study

An approximate analysis following the Vlasov-Leontiev foundation model is developed to evaluate the pile-head stiffness (static and dynamic) of laterally loaded end-bearing pile, embedded in a homogeneous, isotropic, and linear viscoelastic soil with frequency-independent hysteretic material damping. In the analysis, the pile is modeled – a Euler-Bernoulli beam and the soil – a continuum. The horizontal soil displacement fields because of the pile motion is mathematically expressed as a product of separable functions while the vertical soil displacement is ignored for the sake of mathematical simplicity. The contribution of vertical soil displacement on the lateral response is indirectly included in the analysis by a modification of the soil modulus. The Extended Hamilton’s principle is applied to obtain the differential equations governing pile and soil motions, which are solved analytically following an iterative algorithm. The degree of accuracy, and the capability of the analysis to capture the essential mechanics (particularly because of dynamic loading) is assessed by comparing static and complex dynamic pile-head stiffness against other popular analyses developed in the literature. Based on the comparisons, appropriate discussions on the present, and analyses available in literature are provided; further, recommendations on the advantages of this analysis for use in practice are also outlined.

Three‐dimensional analytical continuum model for axially loaded noncircular piles in multilayered elastic soil

AbstractTo investigate the settlement response, load transfer behavior, and geometric effect of noncircular piles, a general three‐dimensional (3D) analytical continuum model for axially loaded noncircular pile‐multilayered homogeneous soil systems is presented. In the analysis, both the vertical and horizontal soil displacement fields are considered, and the variations of the soil displacement components are described by the three displacement transfer functions along the x, y, and z directions. The governing differential equations of noncircular piles and soil are derived by applying the principle minimum potential energy and variational method to the pile‐soil system. A complex variable function conformal mapping technique is introduced to overcome the complex boundary conditions of the transfer functions. Then, the numerical solutions of all the governing differential equations are simultaneously solved following an iterative algorithm. The reliability of this approach is validated by comparing some pile and soil responses with the results from existing analytical solutions or a rigorous finite element analysis. Differences in the settlement response and the axial force distribution between noncircular and circular piles are observed. In addition, the pile shaft resistance along the perimeter of the cross‐sections shows that a greater load is required in order to fully mobilize the ultimate resistance of the noncircular piles. We also compare the stress () contours of some typical noncircular piles with a circular pile, which provides useful insights into the geometric effect.

Numerical Investigation of a Foundation Pit Supported by a Composite Soil Nailing Structure

In special geology conditions such as silt-soil, foundation pits are prone to instability and severe deformation. In this paper, a composite soil nailing structure was studied and its effect on a silt-soil symmetrical foundation pit investigated. The factors affecting the stability of the pit as well as its deformation characteristics were also explored. The results show that excavation depth of the foundation pit has a significant impact on its stability. The soil outside the foundation pit is in the form of a parabola, and the uplift of the soil mainly occurs at the bottom. The horizontal displacement of soil on the side wall of the foundation pit presents a “bulk belly” form. In addition, the axial force of soil nails is larger in the middle part, and smaller at both ends in the shape of a spindle. Moreover, the horizontal displacement is positively correlated with the inclination and spacing of the soil nails, but negatively correlated with the diameter and depth of the mixing pile inlay. Furthermore, the inclination and spacing of the soil nails, the diameter, and embedded depth of the mixing pile have their own critical values for stability of the foundation pit. Specifically, in this paper, with respect to soil nails, inclination should be below 30° and prestress value should not exceed 20 kN. With respect to the mixing pile, the diameter should be less than 1.5 m; when the embedded depth of the mixing pile exceeds the critical depth, the limiting effect of the mixing pile on horizontal displacement is not significant. This research provides important takeaways for the design of a composite soil nailing structure for symmetrical foundation pits.

Discrete element analysis of structural characteristics of stepped reinforced soil retaining wall

Based on the laboratory large scale model test of the stepped reinforced soil retaining wall (RSRW), the discrete element numerical model of stepped RSRW is set up by particle flow code. The displacement of particles, stress distribution, force chain distribution, and potential failure surface of the stepped RSRW are analyzed by simulating the loading process. The results show that the geogrid can confine the horizontal displacement of soil and reinforce soil effectively. The geogrid endures the soil pressure of upside and transmits the pressure to surrounding soil, and improves the distribution of vertical soil pressure of the stepped RSRW. The number of strong force chains in the reinforced area is obviously higher than in the unreinforced area, which verifies that the geogrid can strengthen the soil. The soil particles have been in a plastic flow state and formed a continuous sliding surface at the front of retaining wall, but there was no obvious crack in the retaining wall. The potential failure surface of the stepped RSRW can be determined by observing the changes of force chain structure. The numerical simulation result of the potential failure surface is in good agreement with the theoretical calculation.

Design and verification of a wireless sensing system for monitoring large-range ground movement

In this study, flex sensors and Bluetooth wireless transmission technology were combined to fabricate a wireless sensing system for monitoring ground movement. A typical hinge joint structure was designed and fabricated to embed flex sensors. A number of these typical hinge joint elements were used to measure distributed ground movement. Calibration tests show that minimum resolution, sensitivity, and measurement range of flex sensors were 0.5°, 2.0–2.3 count/° and −30°∼+70°, respectively. In experimental study, five flex sensors were placed inside a slope model for both soil settlement and horizontal displacement measurement. Calculated settlement of the data measured from flex sensors were verified with the output data of Linear Variable Displacement Transducer (LVDT), and the obtained maximum errors were less than 0.5 mm when the maximum ground displacement was approached. Besides, the calulated horizontal soil displacement from measurement of flex sensors has proved that flex sensors can be applied for monitoring soil movement when large ground deformation occurs.

Numerical Study of Seismic Vibrations of Closely Located Buried Large Structures

The paper presents an efficient numerical technique for 3D-modeling of seismic stability of large buried structures. This technique allows considering the subsoil-structure contact interaction, gravity field effects, the inhomogeneous structure of soil and the varieties location of the earthquake hypocenter. As part of this technique is substantiated sizing of the soil-structure computational domain and continuum model for hard and soft soil foundations describing. The numerical technique for determining the kinematic conditions at the lower boundary of the computational domain from the experimental accelerations at the soil surface is given, offered special non-reflecting waves boundary conditions. The methods described above and algorithms for seismic resistance solving have been implemented in certified software package “Dynamica-3”, parallelization of the algorithm has been held according to the spatial domain decomposition principle. The developed numerical technique allows correctly posing the problem of seismic vibrations of buried structure, reducing computing costs and increasing the efficiency of numerical studies of Earthquake Engineering. Through this, the multiple recalculation of the task with different action scenarios generated from experimental seismograms by probabilistic methods became technically possible. The results of these calculations allow reflecting the experience of many earthquakes, which increases reliability of the estimates. The paper presents the model calculations results of seismic stability of large-sized buried structure—the mutual vertical and horizontal displacement of soil and building walls—which can then be used to assess strength of adjacent underground pipelines. A number of numerical experiments on seismic vibrations of nearby large-sized structures have been carried out to assess the mutual influence of structures on their behavior in an earthquake. It is established that the influence of nearby large-sized objects on seismic vibrations of structures differs for different buildings.

Prediction Method of Deep Horizontal Displacement of Slope Soil Based on Damped Holt-Winters Model

The prediction of deep horizontal displacement of slope soil is an important part of slope deformation monitoring, which has important guiding significance for the prevention of slope safety accidents. Holt-Winters model is suitable to predict the data series of deep horizontal displacement of slope soil, which show both trend growth and seasonal fluctuation. Firstly, this paper selected the data set as the original data for empirical analysis which is deep horizontal displacement of soil after pretreatment from the specific slope monitoring project, then used the Holt-winters’ damped model to perform data mining, finally, compared with the traditional prediction methods including the neural-network model and the k-nearest neighbor classification. The results show that the damped Holt-winters model has the highest prediction accuracy.