Soil Deformation Research Articles

Examination of Conditions Controlling Soil Liquefaction and Deformations Caused by Liquefaction

Yapıların deprem gibi doğal afetlerden kaynaklanan hasarlarında, yapıların kalitesi kadar inşa edildikleri zeminin özellikleri de büyük bir önem taşımaktadır. Bu hasarlar arasında yapıların farklı oturmalar yapması, yan yatması, devrilmesi ve zemin içine gömülmesi gibi durumlar yer almaktadır. Bu hasarlara sebep olan en önemli etkenlerden biri, zemin sıvılaşmasıdır. Sıvılaşma, yeraltı suyu seviyesinin altındaki zeminlerin geçici olarak katılığını ve dayanım gücünü kaybederek, bir katıdan ziyade akışkan bir sıvı gibi davranması sürecidir. Bu çalışmada öncelikle sıvılaşmanın mekanizmasından ve tarihçesinden, sıvılaşma çeşitlerinden bahsedildikten sonra sıvılaşma için gerekli koşullar detaylı olarak incelenmiştir. Sıvılaşmadan dolayı meydana gelebilecek zemin hareketlerinin incelenerek, bu hareketler sonucunda meydana gelen deformasyonlar ve sıvılaşma etkilerinin nasıl azaltılacağına yönelik alınacak önlemler incelenerek ortaya konulmuştur.

A 3-DOF system for preliminary assessments of the interaction between base isolation (BI) technique and soil structure interaction (SSI) effects for low-rise buildings

Base isolation technique is based on two mechanisms: period elongation and damping increase that may considerably improve the structural performance under earthquakes. However, the effectiveness of BI may be significantly reduced by the deformability of the foundation soil and thus by soil structure interaction (SSI) effects. In this regard, considering the role of the mutual interaction between BI and SSI becomes fundamental to realistically design structural systems. In literature, the assessment of the mutual role of BI and SSI is conducted with advanced numerical simulations that require realistic definitions of the non-linear properties of the structures, the isolation system and of the soil layers. However, these methods are extremely time-consuming and more expeditious methodologies are necessary. In this paper a 3-DOF system is proposed to perform preliminary assessments for design purposes. Parametric case studies have been proposed to demonstrate the potentiality of the proposed method to represent the cases where the beneficial effects of BI are reduced and eventually when BI technique becomes detrimental.

Influence of Static and Repeated Surface Surcharge Loadings on Tunnel Displacement Considering Small-Strain Stiffness of Soft Clay

With the rapid development of urban metro tunnels, the effect of surface surcharge loading on existing tunnels is unavoidable. Accurate evaluation of soil deformation and tunnel displacement under surface surcharge loading is of great significance for practical engineering. In this research, the effect of static and repeated surface surcharge loadings on tunnel displacement in soft clay was investigated numerically. The hardening soil model with small-strain stiffness (HSS model) was adopted to simulate the soil response. The parameters of the HSS model were obtained through geotechnical tests. The result indicates that Shanghai layer 4 soft clay exhibits large soil shear stiffness in the small strain range. Tunnel displacement is closely related to parameters of surface surcharge loading width, burial depth of tunnel, and the horizontal distance from the centerline. The overlapping influence range of tunnel displacement was proposed. Under repeated surface surcharge loadings, the first cycle of the repeated surface surcharge loading has the greatest effect on the tunnel displacement, and the subsequent cycles of loadings still cause further increases in the tunnel displacement. The effect of repeated surface surcharge loadings on tunnel displacement gradually decreases as the burial depth of tunnel and the number of cycles increase.

Numerical implementation of the hypoplastic model for SPH analysis of soil structure development in extremely large deformation

The extremely large deformation of soil is a significant challenge due to the dynamic changes in soil structure, but it is poorly understood owing to inadequate effective numerical methods. This paper presents a numerical method for analysing the responses of sand-like granular soil undergoing extremely large deformation. The proposed method utilizes the Smoothed Particle Hydrodynamics (SPH) technique, which is a meshfree particle-based approach capable of circumventing the computational difficulties associated with mesh distortion. The Gudehus-Bauer (G-B) hypoplastic model, which can capture the pressure- and density- dependent mechanical behaviour of granular soil, is implemented into the in-house developed SPH code. Concerning the characteristics of large deformation, the Green-Naghdi rate is applied in this study to achieve objective stress integration. An adaptive explicit stress integration scheme, termed Modified Euler automatic Substepping with Error Control (M-E-SEC) is utilized to handle the time integration of the SPH equation system. Additionally, a stability correction method is introduced to suppress the breakdown problem that occurs at low-stress states. The effectiveness of the proposed method is validated by experimental data. Furthermore, several numerical examples are presented to elucidate the evolution of shear band structures in granular soils subject to extremely large deformation levels.

РАСЧЕТНАЯ МОДЕЛЬ ДЕФОРМИРОВАНИЯ ГРУНТОВОГО ОСНОВАНИЯ ВЫСОТНОГО ЗДАНИЯ С УЧЕТОМ ПРЕДЫСТОРИИ ЗАГРУЖЕНИЯ

While designing high-rise buildings, it is necessary to take into account the influence of stages of their erection, this is the sequence of loading, on the change in physical-mechanical properties of soils. The calculation of deformations of subgrade is made with due regard for the change in soils properties comparing with the initial (natural) state. On the basis of the results of experimental studies, the authors substantiate the necessity for introducing the new parameter which makes it possible to characterize the mechanical condition of the soil at any stage of loading and can be used for creating calculation models. An analytical diagram of soil deformation in coordinates «σ1–ε1» for triaxial compression (where σ1 – vertical stresses (deviator), ε1 – linear deformations under the triaxial compression) is adopted as this parameter. The procedure for constructing transformed diagrams of the soil state under the long performance triaxial loading is described. The procedure obtained was approbated when calculating deformations of the foundation base of the high-rise building with due regard for the influence of staging of construction and rheological properties of soils on the change in the base rigidity and, as a result, on the redistribution of stresses among separate elements of the system “subgrade –foundation – upper part of the building.

A Modified Method for the Fredlund and Xing (FX) Model of Soil-Water Retention Curves

The soil-water retention curve (SWRC) is fundamental in presenting the hydromechanical characteristics of soils, which are closely connected with soil deformation, permeability, and shear strength. The Fredlund and Xing (FX) model accurately fits the SWRCs of different types of soils over a wide suction range. However, experimental comparisons of the fitting showed that the obtained parameters differ from the physical meanings assigned by Fredlund and Xing. To address this issue, the traditional FX model has been improved, resulting in the proposal of a two-step FX model. Firstly, the FX model is applied without taking the correction coefficient c(ψ) into account to fit the measured SWRC. The values for α, n, and m are then determined and substituted into the FX model to refit the experimental data. Finally, the last parameter Cr can be obtained. The curves resulting from these two steps have a good agreement with the experimental results, and the obtained parameters align better with their physical meanings.

Plaxis 2D Modelling of an Anchor Sheet Pile for Soil Slope Strengthening at Segamat, Johor

In soil engineering, the soil slope is one of the important issues in geotechnical and environmental engineering that can fail due to settlement behaviour. Due to soil slope instability, roads near the Segamat River’s slopes have seen severe settlement. Therefore, this study was carried out to determine how the geometry of the soil slope and the properties of the soil affect soil stability and deformation. Because of the varying slope geometries along the river, this study used two alternative slope geometries in its modelling. A comparison was made between the existing slope and the slope stabilised with sheet piling by using Plaxis 2D. Other parameters that affect slope stability are also being investigated, such as anchor length and anchor installation angle. The anchor sheet pile's presence is intended to improve the slope's stability. As a result of this analysis using PLAXIS 2D software, the optimal anchor length depends on the passive pressure of the soil behind the sheet pile. According to the results, installing an anchor with a 60° angle is more stable because the safety factor obtained is 3.26 which is greater than that of a 45° angle which is 1.33. It shows the anchor is the best support of the sheet pile for the soil slope stability.

Peculiarities of using the hypothesis of S.O. Kulon for soil dispersed sediments

The publication is devoted to the outstanding French scientist Charles Auguste Coulomb, who 250 years ago (1773) proposed a hypothesis that relates tangential and normal stresses through the angle of internal friction of soils. This hypothesis provides reliable results while maintaining Hooke's law. Beyond this law, it is necessary to take into account the property of the soil medium, namely the change in volume during shearing or displacement of soils, which requires the introduction of additional dilatancy parameters.
 It is known that there are two types of friction in nature: sliding and rolling friction. At certain values of deformation in the soil medium, sliding friction, which is characterised by the traditional value of the internal friction angle, initially appears in certain zones of the soil medium at low deformations. Further increase in deformation causes rolling friction, which is characterised by a different value of the internal friction angle, almost one third less than the traditional value of the internal friction angle of the soil. This fact must be taken into account when performing numerical modelling of a dispersed soil medium from the beginning of loading to its failure. In this publication, we discuss the methodology for finding the parameters of the dilatancy theory to reveal the elastic-plastic deformation of cohesionless soils based on experimental results. Recommendations are given on the use of the Coulomb hypothesis in engineering calculations and on the relationship between tangential and normal stresses through the angle of internal friction of soils. For a correct description of the nonlinear process of soil deformation, it is necessary to use the parameters of the dilatancy theory, which can be investigated on an axisymmetric shear tester.
 The results of tests of sand of medium size, medium density, low-moisture, homogeneous on several devices showed that the values of the angle of internal friction of soils differ depending on the design of the device. This fact is recommended to be taken into account when designing geotechnical facilities.

Microchannel‐Confined Chinese Ink‐Based Highly Stretchable Liquid‐State Strain Sensor for Early Warning of Road Collapse

AbstractStretchable strain sensors are widely used in the fields of wearable devices, soft robotics, healthcare monitoring, and more. Despite tremendous efforts, strain sensors capable of detecting large‐scale soil deformation for urban geological hazard prevention have not yet been demonstrated. In this paper, a soft strain sensor of a highly stretchable Ecoflex‐0030 elastomeric matrix with microchannel‐confined environmentally benign conductive Chinese ink as the liquid‐state strain‐sensitive material that can reliably detect a wide range of working strain up to 300% is demonstrated. The sensor exhibits a negligible hysteresis error of 2.1%, with a considerably good gauge factor of 1.95. The sensor performance is evaluated under both creep and cyclic loading tests, indicating superior stability (0.65% fluctuation), and repeatability (0.28% variation in 1000 cycles), even under a lower underground environment temperature of 18°C. As a proof‐of‐concept demonstration, a liquid‐state strain sensor array with a strain amplification mechanism capable of accurately monitoring the formation of various underground cavities and providing timely demanded information for early warning of catastrophic road collapse is demonstrated and verified by the computer vision‐based particle image velocimetry (PIV) method.

Dependence of Tractor Traction Properties on Agricultural Machinery Connections

Tractor traction properties depend on many factors including engine power, operating weight and tractor weight distribution across axles, dimensions, profile, gears range and gear count in the gearbox. Moreover, the tractor technical condition plays a vital role, encompassing aspects from the fuel system affecting the engine power output, to the chassis, influencing terrain traversability, maneuverability, and soil deformation. (Research purpose) The paper addresses several research problems. To investigate the impact of the agricultural machinery connections with the tractor on the tractor traction properties, and determine the impact of agricultural machinery weight, and grip width on the main technical and economic parameters. To analyze how geometrical parameters of tractors and agricultural machinery correlate with soil reactions under the machine support wheels as well as the front and rear wheels of the tractor. To determine the influence of the design characteristics of cultivators with varying working widths on the main operational properties of the machine-tractor unit. (Materials and methods) The study involves examining the operation of the Belarus 82.1 tractor with cultivators KPS-4 and KPS-5 from different manufacturers. Various methods were employed, including calculation, calculation-construction, calculation-graphic analysis, economic-mathematical techniques, along with comparison, measurement, and description. (Results and discussion) This study identified indicators impacting the load redistribution transmitted to the tractor from mounted cultivators. Based on these indicators, alterations in soil reactions under cultivator support wheels and the tractor’s rear wheels were deduced. (Conclusions) The calculations on the effect of mounted cultivators with different working widths (different operating weight) on the redistribution of soil reactions between axles, enabled the determination of modifications in tractor traction force, machine-tractor unit productivity, and specific fuel consumption.

Multicore CPU-based parallel computing accelerated digital image correlation for large soil deformations measurement

This paper presents a new approach for measuring large deformations in geotechnical experiments employing digital image correlation (DIC) or particle image velocity (PIV) techniques. The proposed method is based on the Eulerian analysis scheme, allowing for the application of multicore central processing unit (CPU)-based parallel computing to expedite the processing of experimental images. The displacement increments obtained through DIC analysis on the Eulerian mesh nodes (subset centers) are then mapped onto tracer particles (TPs), which are assigned by users to track material movement. Finally, accumulated displacements and strains are determined on these TPs. Two example applications are presented to showcase the capabilities of the proposed method: a centrifuge half model test of flat circular footing penetrating sand overlying clay and a full transparent soil model test (TMST) of conical pile penetration. A comparison with other standard first-order deformation algorithms and the Lagrangian analysis scheme demonstrates that the presented method offers comparable precision but significantly faster computation speed, with an improvement of over six times when processing a considerable number of (e.g. over 20) images. This enhanced computational speed can greatly reduce the time required for image post-processing. The proposed method is particularly suitable for large deformation experiments that involve the analysis of numerous images and require high precision.

Effects of vertical load and inflation pressure on tire-soil interaction on artificial soil

Instrumented single tire soil bin testing was conducted on a rigid surface and artificial soil by vertically loading a radial tire (LT235/75R15) to two tire vertical loads (6 kN and 8 kN) inflated to three levels of tire inflation pressure (179, 241, and 283 kPa). Lowering the tire inflation pressure by 37 % resulted in 26 % (6 kN vertical load) and 39 % (8 kN vertical load) greater contact lengths (P < 0.05). The 2-D contact area on artificial soil (initial bulk density of 1.51 Mg/m3) was significantly affected (P < 0.05) by tire inflation pressure for each load case. Increasing the load significantly affected the tire’s contact length on soil (P = 0.0010); however, tire inflation pressure did not significantly affect the contact length on soil (P = 0.0609). Soil rut depth and tire-soil deformed volume were not significantly affected by vertical load and tire inflation pressure. Measured tire contact area on soil surface was 3.3 times the contact area on the rigid surface, suggesting tire-soil interaction interface properties on deformable soil are better than using the gross flat plate for evaluating low ground pressure tire technology effects on traction and reducing soil compaction.

Cementation of soils by wristband-pipe injection technology in conditions of thawing perpetually frozen soils

In the conditions of global warming of the climate in the territories of permafrost distribution it takes place the processes of increasing the temperature of perpetually frozen soils and increasing the depth of their thawing. These factors lead to a decrease in the structural safety of the buildings and constructions. Measures to return soils to the frozen state are not always feasible and effective. In such conditions the solution to the problem of decreasing the pile foundation bearing capacity can be the ground strengthening by the cementation using the wristband-pipe injection technology. In the article it is presented the experience of assessing the current technical condition and designing of bases and foundations strengthening of a three-storey residential building in Yamal-Nenets Autonomous District, village Muzhi. The object was given a limited-operational category of the technical condition due to the deficit of the pile foundation bearing capacity. To bring the constructions of the object to the working condition the project of pile foundation strengthening with the cementation by wristband-pipe injection technology was developed. While injecting the soil foundation with the hydraulic fracturing the additional (induced) tension state appears, and it changes the deformation and strength properties of soils, voids ratio, index of liquidity and modulus of deformation. Reinforced joints, soil compaction and stabilization appear due to the injection. While making the hydraulic test and fracturing in the soil body its stress and strain state is changing, foundation piles are stressed with the additional lateral pressure. Besides the soil is strengthening under the pile toe bulb. Analytical calculations are given for increasing the bearing capacity of a pile during cementation of soils due to the increase of horizontal stresses and the work of compacted foundation soil on the lateral surface and under the lower end of the pile.

Micromechanical investigation of the effect of an imposed stress state change during drained cyclic loading using DEM

This study investigates the effect of a stress state change at an intermediate stage during cyclic loading on the drained cyclic deformation of soil using Discrete Element Method (DEM) simulations. Drained cyclic triaxial simulations were conducted on an assembly of irregularly shaped particles, with the stress state shifting along different stress paths at an intermediate stage of cyclic loading. The analysis of the macro- and microscopic responses reveals a link between the cyclic stress–dilatancy behaviour and the anisotropy of the granular assembly. In the simulations without the stress state change or with a stress ratio increase, the strain accumulation direction aligns with the prediction of the Modified Cam Clay (MCC) flow rule; and the strain accumulation is faster at higher stress ratios when the contact distribution is more anisotropic. However, when the particle assembly experiences a stress ratio decrease during cyclic loading, the subsequent strain accumulation direction deviates from the MCC flow rule, and strains accumulate more rapidly at lower stress ratios when the contact distribution is nearly isotropic. A tentative explanation is proposed to explain the altered strain accumulation direction after the stress ratio decrease.

Nonlinear deformations of the compacted soil base under the broadening of piles in punched holes

The peculiarity of piles in punched holes with broadening (PPH), performed according to the technology of foundations in rammed pits, is considered to be a high load-bearing capacity compared to traditional driven piles. At the same time, from the long-term practice of using the PPH, the actual excess of the calculated settlement is noted. This is due to a significant excess of pressure of the order of 1,000-3,000 kPa under the widening of the pile over the calculated resistance of the compacted soil layer. This makes it necessary to calculate such a foundation for the second group of limit states, taking into account the nonlinearity within the limits of the calculated allowable pressure. The article compares three methods of calculating settlement taking into account non-linearity: according to the tables of the standard, the methods of N.V. Ornatsky and M.V. Malyshev. It is noted that the methods do not always correspond to the actual work of the foundation in the ground, which can reduce the reliability of calculations. The authors proposed to modernize the existing methods of calculating settlement due to the peculiarities of the work of the PPH. In the calculation scheme of the PPH, to determine the settlement, it is necessary to take into account the soil layer with an increased modulus of deformation created during the punching of the well and the formation of broadening. Zones of marginal equilibrium develop with a margin within the boundaries of the compacted layer under broadening. It is proposed to take into account the nonlinear dependence of soil deformations on stresses within the specified boundaries, and to take into account the remaining deformations of the compressible thickness in a linear formulation. Taking into account the non-linearity in the determination of settlement leads to an increase in the reliability of the application of the piles in question, especially in weak clay water-saturated soils, and in relatively strong soils allows us to confirm the reliable use of PPH.

Obtaining the empirical calibration dependence for express assessment of the quality of the performance of ground structures

In this study, the authors consider sand pads, namely the production process and quality control. The main problem of using the compacting factor as a criterion for assessing the quality of sand pads is the impossibility of calculating future deformations of foundations, as well as the duration of laboratory studies to determine it. Thus, the development of a technological solution for the use of express methods for controlling the compaction of soil structures, which are based on empirical data and can reduce the economic costs of construction, is an urgent task. The direct object of the study is the sand pad under the production facility. In the process of installing a sand pad, layer-by-layer control of the degree of compaction was carried out according to the compacting factor with the determination of the maximum density according to the method of GOST 22733-2016, and the modulus of soil deformation according to selected soil samples for compression tests. For each layer, the compaction coefficient was determined at 5 points, the deformation modulus at 3 points. Additionally, tests were carried out using a dynamic density meter. The main result of the study is the construction of a calibration dependence of the constrained modulus on the dynamic modulus of elasticity of the soil based on the results of statistical processing. Based on the test results, it was found that the experimental data are equally accurate, the resulting model is adequate. The difference between the experimental data and the calibration dependence does not exceed 18 %, which is a good convergence for empirical methods. The obtained experimental dependence allows, with a sufficient degree of accuracy, to quickly control the quality of the sand pad.

Evaluation of deformation and strength parameters of organic soils for the design of geotechnical structures

The evaluation of deformation and strength parameters of Holocene organic soils obtained from DMT dilatometer tests based on empirical relationships and ANN Artificial Neural Networks is presented. The evaluation of undrained shear strength τfu, deformation modulus E0.1% and initial shear modulus G0 of Eemian organic soils obtained from DMT dilatometer tests and SDMT seismic dilatometer tests is given, and then its comparison with the values obtained from triaxial tests for the design of underground structures supported by diaphragm walls of the stations of the underground line II in Warsaw, is shown.

Simplified analytical solution for time dependent deformation of soft soil improved with pervious column considering load transfer between column and soil

This paper presents a simplified analytical solution to analyse the coupled excess pore water pressure dissipation and deformation response of a composite stone column – soft soil foundation. The mathematical formulation is derived considering the combined radial – vertical flows of excess pore water pressure in stone column and soft soil areas (orthotropic permeability for each area), and adopting the settlement pattern for the composite ground suggested by an existing study in the literature. The homogeneous consolidation formulations are solved first to develop Green’s function for final excess pore water pressure solutions, employing the method of separation of variables and eigenfunction expansion technique. Then, the final solutions for excess pore water pressure corresponding to the nonhomogeneous consolidation formulations are derived in terms of Green’s formula, which can be expanded readily into a double series solution. The obtained analytical solutions can be used to examine the variation of excess pore water pressure against time at any point in the composite foundation. Thus, the consolidation settlements of stone column and soft soil areas and the differential settlement between them can be captured. The average differential settlement between the soil and column areas is used to compute the shear strains and shear stresses in the composite ground during the consolidation process. The proposed analytical solution is validated via a worked example in conjunction with a verification exercise against finite element simulation. The analytical predictions are presented in terms of the total vertical stress variations and excess pore water pressure dissipations against depth and time, the settlements and average degrees of consolidation for stone column and surrounding soft soil, and the shear stress distribution in the soil region. The capability of proposed analytical solution is also verified against field measurements of a full-scale test of soil - column composite ground (pervious column). The verifications show that the obtained analytical solution can predict the coupled excess pore water pressure dissipation – deformation response of soft soils improved by pervious columns such as stone columns and soil- deep cement mixing columns reasonably well.

A Method for Predicting the Load Interaction between Reinforced Thermoplastic Pipe and Sandy Soil Based on Model Testing

This study aims to investigate the interaction between reinforced thermoplastic pipes (RTPs) and sandy soil. The mechanical properties of sandy soil in the South China Sea region were determined through shear tests to obtain fundamental data. Subsequently, a specialized experimental setup was designed and assembled to study the pipe–soil interaction, specifically measuring the lateral soil resistance of flexible pipes at varying burial depths. Data analysis revealed the relationship between soil resistance, lateral displacement, and initial burial depth. To simulate the mechanical behavior of the pipe–soil interaction, the coupled Eulerian–Lagrangian (CEL) method was employed for numerical simulations. The research findings indicate that the lateral soil resistance is influenced by the uplift height and accumulation width of the soil ahead of the pipe. Within a lateral displacement range of 0.5 times the pipe diameter (0.5D), the lateral soil resistance rapidly increases, resulting in a soil uplift along the circumferential direction of the pipe. This process not only enhances the load-bearing capacity of the pipe but also increases the accumulated soil resistance, consequently expanding the soil failure zone. Furthermore, the ultimate soil resistance exhibits an increasing trend with an increasing burial depth. Once the pipe reaches a certain burial depth, the uplift height of the soil reaches a critical state. To address the grid distortion caused by soil deformation, numerical simulations based on the CEL method effectively modeled the pipe–soil interaction forces under significant lateral displacements, exhibiting good agreement with the experimental results. This study provides a solution for investigating soil resistance in submarine pipelines, thereby contributing significantly to the design and performance prediction of underwater pipelines.

Determining parameters of peat soil for finite-element analysis using the Cam Clay model

A practical procedure for determining soil parameters when analysing the deformation of peat by finite-element analysis (FEA) using the Cam Clay model is presented. FEA has not been frequently used to predict the deformation of peat soil, even though it can be a powerful prediction tool. The main reason for this is that a practical method for determining parameters has not been established. In this paper, the remarkable correlation between the soil parameters required for FEA using the Cam Clay model and the natural water content (wn) and ignition loss (Li) of peat and organic clay is presented. Then, based on this correlation, a flow chart for determining the soil parameters of peat and organic clay is proposed. Using this chart, it is possible to determine soil parameters directly from triaxial compression, oedometer and other detailed tests or to estimate them from wn, Li and other physical indexes. A trial embankment on peat soil in Hokkaido, Japan, was also created. FEA was performed on the trial embankment using the proposed procedure for determining the soil parameters. The results of the FEA corresponded to the measured settlement behaviour in the trial embankment with an accuracy in the range −4% to +8%. The FEA results also modelled the measured behaviour of pore water pressure and lateral and vertical displacements in the trial embankment very well.