Showing papers in "International Journal of Geomechanics in 2014"

Behavior of fresh and fouled railway ballast subjected to direct shear testing: discrete element simulation

Abstract: This paper presents the three-dimensional discrete element method (DEM) that was used to study the shear behavior of fresh and coal fouled ballast in direct shear testing. The volumetric changes and stress-strain behavior of fresh and fouled ballast were simulated and compared with the experimental results. Clump logic in particle flow code in three dimensions (PFC3D) incorporated in a subroutine was used to simulate irregular-shaped particles in which groups of 10–20 spherical balls were clumped together in appropriate sizes to simulate ballast particles. Fouled ballast with a various void contaminant index (VCI) ranging from 20 to 70% VCI was modeled by injecting a specified number of miniature spherical particles into the voids of fresh ballast. The DEM simulation captures the behavior of fresh and fouled ballast as observed in the laboratory, showing that the peak shear stress of the ballast assembly decreases and the dilation of fouled ballast increases with an increasing VCI. Furthermore, th...

Effect of Slope and Loading Direction on Laterally Loaded Piles in Cohesionless Soil

Abstract: An extensive program of laboratory model tests was undertaken to study the effect of slope and loading direction on laterally loaded piles in cohesionless soil. The paper includes studies of the effect of distance from the crest of the slope (both slope side and embankment side), soil properties, and loading direction (both forward in the direction of the slope and reverse loading). The pile lateral capacity in sloping ground was compared with that in horizontal ground. From the experimental investigation, it is observed that when piles installed in sloping ground undergo forward loading, lateral capacities of the piles are almost reached at 8% of the pile diameter in loose-to-medium dense soil and 16% of the pile diameter in dense soil. If the pile is placed >15 times the pile diameter away from the slope crest within the embankment, the influence of slope in the lateral-load capacity is almost negligible under both forward and reverse lateral load.

One-Dimensional Consolidation of Unsaturated Soil Subjected to Time-Dependent Loading with Various Initial and Boundary Conditions

Abstract: This study assesses the one-dimensional (1D) consolidation of unsaturated soil subjected to time-dependent loading based on the 1D consolidation theories of unsaturated soil. The differential quadrature method (DQM) is used to produce a general solution that considers various boundary conditions, various initial pore-water and pore-air distributions, and complex time-dependent loading. A special case in which the analytical solution is available in the literature is used for verification and accuracy analysis. It is found that the DQM solution can deliver more accurate results compared with the finite-difference method with a small number of sampling points. The general solution can avoid cumbersome computations in solving eigenequations encountered with the analytical solution. In addition, the proposed solution is more suitable for practical engineering because of its generality in complex initial, boundary, and loading conditions. Finally, the characteristics of the 1D consolidation of unsatura...

Prediction of Undrained Monotonic and Cyclic Liquefaction Behavior of Sand with Fines Based on the Equivalent Granular State Parameter

Abstract: The undrained behavior of sand with fines under both monotonic and cyclic loading was investigated experimentally by triaxial testing. The testing program covers fines content ranging from 0 to 30%, and a wide range of initial void ratios and confining stresses. The spectrum of cyclic loading includes one- and two-way cyclic loading, and in the latter case, the cyclic loading may be symmetrical or nonsymmetrical. The influence of fines content can be captured by using the equivalent granular void ratio, e∗, in lieu of the void ratio, e. All steady-state data points can be described by a single relationship referred to as the equivalent granular steady-state line. This study proposes the concept of the equivalent granular state parameter, ψ∗, for capturing the combined effects of the stress state, density state, and fines content. The observed behavior can then be related to e∗ and/or ψ∗. Irrespective of fines contents, the behavior under monotonic loading can be classified into three types, and ψ∗...

Fully Nonlinear versus Equivalent Linear Computation Method for Seismic Analysis of Midrise Buildings on Soft Soils

Abstract: In this study, the accuracy of a fully nonlinear method against an equivalent linear method for dynamic analysis of soil-structure interaction is investigated comparing the predicted results of both numerical procedures. Three structural models, including 5-story, 10-story, and 15-story buildings, are simulated in conjunction with two soil types with shear-wave velocities less than 600 m/s. The aforementioned frames were analyzed under three different conditions: (1) fixed-base model performing conventional time history dynamic analysis under the influence of earthquake records, (2) flexible-base model (considering full soil-structure interaction) conducting equivalent linear dynamic analysis of soil-structure interaction under seismic loads, and (3) flexible-base model performing fully nonlinear dynamic analysis of soil-structure interaction under the influence of earthquake records. The results of these three cases in terms of average lateral story deflections and interstory drifts are determine...

Bearing Capacity of Strip Foundations in Reinforced Soils

Abstract: A method is proposed to determine the ultimate bearing capacity of a strip footing placed over granular and cohesive-frictional soils that are reinforced with horizontal layers of reinforcements. The reinforcement sheet is assumed to resist axial tension but not bending moment. The analysis was performed by using the lower bound theorem of the limit analysis in combination with finite elements. A single layer and a group of two layers of reinforcements were considered. The efficiency factors ηγ and ηc that need to be multiplied with the respective bearing capacity factor Nγ and Nc to account for the inclusion of the reinforcements were established. The results were obtained for different values of the soil internal friction angle (ϕ). The critical positions of the reinforcements, which would result in a maximum increase in the bearing capacity, were established. The required tensile strength of the reinforcement to avoid its breakage during the loading of the foundation was also computed. The resu...

Modeling Cyclic Behavior of Rockfill Materials in a Framework of Generalized Plasticity

Abstract: Typical triaxial compression experiments were revisited to investigate the essential mechanical behavior of rockfill materials to be reflected in constitutive modeling, such as the nonlinear dependence of the strength and the dilation on the confining pressure and the accumulation of permanent strains during cyclic loading. The mathematical descriptions of the axial stress-strain behavior during initial loading, unloading, and reloading were formulated, respectively, which enables us to represent the hysteresis loops directly without recourse to complex concepts and parameters. The axial stress-strain model was then incorporated into the constitutive framework of generalized plasticity for the modeling of cyclic behavior of rockfill materials. This task was fulfilled by defining the elastic modulus, the plastic flow direction tensor, the loading direction tensor, and the plastic modulus for different loading conditions. In particular, the plastic flow direction tensor was derived based on a stress...

Effect of the Flow Rule on the Bearing Capacity of Strip Foundations on Sand by the Upper-Bound Limit Analysis and Slip Lines

Abstract: The influence of the flow rule on the bearing capacity of strip foundations placed on sand was investigated using a new kinematic approach of upper-bound limit analysis. The method of stress characteristics was first used to find the mechanism of the failure and to compute the stress field by using the Mohr-Coulomb yield criterion. Once the failure mechanism had been established, the kinematics of the plastic deformation was established, based on the requirements of the upper-bound limit theorem. Both associated and nonassociated plastic flows were considered, and the bearing capacity was obtained by equating the rate of external plastic work to the rate of the internal energy dissipation for both smooth and rough base foundations. The results obtained from the analysis were compared with those available from the literature.

Combined FEM/DEM Modeling of Triaxial Compression Tests for Rockfills with Polyhedral Particles

Abstract: Using a microscopic modeling approach, a simplification of the discrete element’s shape was done by using irregular convex polyhedrons to reproduce the geometry-dependent behavior of rockfills. Numerical modeling of the triaxial compression tests was conducted using a combined FEM and discrete-element method (FEM/DEM). The micromechanical properties of the numerical sample were calibrated to match the macroscopic response of the real material. The numerical results quantitatively agree with the laboratory results, which reproduce typical features of the mechanical behavior of rockfills, such as nonlinear stress-strain relationship, compaction, and shear dilatancy. The combined FEM/DEM simulation provides an opportunity for a quantitative study of the microstructure of particle assemblages, which give a better understanding of the mechanical characteristics of rockfills.

Undrained Stability of Dual Circular Tunnels

Abstract: In this paper,numericallimit analysis and semianalytical rigid blocktechniques are used toinvestigate the effectof the tunnelspac- ingonthestabilityoftwocirculartunnelsexcavatedsidebyside.Thetunnelsaremodeledunderplane-strainconditions,whichimpliesthatthey are assumed to be infinitely long. Bounds on the stability of the tunnels are obtained using finite-element limit analysis, the numerical formu- lation of which is based on the upper and lower bounds theorems of classical plasticity. Solutions are obtained using advanced conic program- mingschemes tosolvethe resultingoptimization problems,and upperand lowerboundestimates on thestabilityof thetunnels areobtained for arangeofgeometries.Thesebounds,whichbracketthetruecollapseloadfromaboveandbelow,arefoundtodifferbyatmost5%forthecases where the solution does not approach zero. Results from this study are summarized in stability charts for use by practitioners. DOI: 10.1061/ (ASCE)GM.1943-5622.0000288. © 2014 American Society of Civil Engineers. Author keywords: Tunnels; Stability; Limit analysis; Finite-element method (FEM).

Generalized solution for mining backfill design

Abstract: Underground backfill plays an important role in the mining industry, and is one of the key elements in the routine operation of many underground mines. Its main role is to improve ground stability and reduce ore dilution. Its other advantages include the reduction of surface mining waste disposal, which in turn reduces and even eliminates some problems, such as tailing dam failure or acid mine drainage (AMD), associated with mining waste management. To ensure a safe and economical backfill design, the strength of the backfill must be high enough to allow it to remain stable during the exploitation of adjacent stopes, at the very least. This minimum required strength is usually estimated using a solution proposed in the early 1980s. However, this solution includes several limitations, including the following: it assumed a zero friction angle of backfill; it neglected the surcharge on top of the exposed backfill; it assumed an equivalency between the backfill cohesion and the bond cohesion (adherenc...

New Load Transfer Hyperbolic Model for Pile-Soil Interface and Negative Skin Friction on Single Piles Embedded in Soft Soils

Abstract: A proper load transfer model describing the pile and surrounding soil interaction is important for accurately predicting the behavior of piles. In this paper, a new load transfer hyperbolic model for the pile-soil interface is developed based on soil-structure interface tests reported in the literature, which consider the characteristics of increasing initial shear stiffness, the development of shear strength at the pile-soil interface, the loading, step by step loading, unloading, and reverse loading shearing behavior of the pile-soil interface with consolidation. The proposed model was validated by the close agreement between the computed results and published case histories. Further studies based on the proposed model considering negative skin friction on single piles under pile head load and/or surcharge were subsequently conducted. It was found that the pile-soil interface undergoes complicated shearing, and the depth of the neutral plane (NP) and the skin friction along the pile shaft vary during consolidation. The magnitude of the pile head load and pile installation time has a significant impact on the depth of the NP and the dragload. Pile capacity was shown to decrease with consolidation.

Lower-Bound Limit Analysis of Seismic Passive Earth Pressure on Rigid Walls

Abstract: Static and seismic passive earth pressure coefficients for the general case of an inclined wall and a sloping cohesionless backfill were computed by using finite-element lower-bound limit analysis based on second-order cone programming (SOCP). The comparison with the best existing upper-bound solution and the widely accepted solution obtained by the method of stress characteristics has shown that the present lower-bound solutions can provide a safe estimate of the passive earth pressures. Therefore, combining present results and upper-bound solutions can bracket the true value of passive earth pressures. In addition, design tables are presented that allow geotechnical engineers to easily use the present results in practice.

Bearing Capacity of Strip Footings in Cohesionless Soil Subject to Eccentric and Inclined Loads

Abstract: Lower-bound calculations based on the FEM are used to determine the bearing capacity of a strip foundation subjected to an inclined, eccentric load on cohesionless soil with varying surcharges and with friction angles of 25, 30, and 35°. The soil is assumed to be perfectly plastic following the Mohr-Coulomb failure criterion. The results are reported as graphs showing the bearing capacity as a function of the friction angle, eccentricity, inclination, and surcharge. These results have been compared, and for smaller eccentricities, except in the case of no surcharge, the lower-bound values are the greater, the discrepancy increasing with growing surcharge. Positive load inclinations have a negative effect for smaller eccentricities but may have a beneficial effect on the bearing capacity for greater eccentricities. Negative load inclinations have the opposite effect, and especially for small friction angles and great surcharges, other values are considerably greater than the lower-bound values.

Testing and Modeling the Behavior of Riverbed and Blasted Quarried Rockfill Materials

Abstract: Modeled rockfill materials were obtained from nine sites (two riverbed and seven quarried) from different projects in India and Nepal, and drained triaxial tests were conducted with specimens that were 381 mm in diameter and 813 mm high. Index properties of the rockfill materials, namely, unconfined compressive strength (UCS) and uncompacted void content (UVC), were determined. An elastoplastic hierarchical singe-surface (HISS) constitutive model was used to characterize the behavior of modeled rockfill materials. The predicted stress-strain-volume change behavior was compared with the observed behavior, and it was found that both observed and predicted behavior matched closely. Procedures have been developed to predict the shear strength and elastic parameters of rockfill materials using the index properties, namely, UCS, UVC, and relative density (RD), and predictions were made satisfactorily. Predicted shear strength and elastic parameters were compared with the experimental values, and it was ...

Modeling of the FWD Deflection Basin to Evaluate Airport Pavements

Abstract: The falling weight deflectometer (FWD) testing develops a deflection basin on the pavement surface. Depths of this deflection basin from the center of the falling weight are measured at different radial offsets. These deflections are used for the backcalculation of the pavement layer moduli. Most of the available backcalculation software uses the layered elastic theory and static load to calculate moduli from known pavement surface deflections. However, the FWD test load is dynamic, and layer materials may show nonelastic behavior. Layered elastic theory in these types of software cannot characterize dynamic response of the pavement. Also, elastic theory is unable to accurately predict the surface deflection whenever stress developed in any pavement layer exceeds the yield point. For this reason, this study has performed a finite-element analysis of the airport pavement under the FWD test considering the dynamic load and materials plasticity. The analysis presented here includes elastoplastic beha...

Discrete Element and Experimental Investigations of the Earth Pressure Distribution on Cylindrical Shafts

Abstract: Experimental and numerical studies have been conducted to investigate the earth pressure distribution on cylindrical shafts in soft ground. A small-scale laboratory setup that involves a mechanically adjustable lining installed in granular material under an axisymmetric condition is first described. The earth pressure acting on the shaft and the surface displacements are measured for different induced wall movements. Numerical modeling is then performed using the discrete element method to allow for the simulation of a large soil displacement and particle rearrangement near the shaft wall. The experimental and numerical results are summarized and compared against previously published theoretical solutions. The shaft-soil interaction is discussed, and conclusions regarding soil failure and the earth pressure distributions in both the radial and circumferential directions are presented.

Behavior of a Pressure-Grouted Soil-Cement Interface in Direct Shear Tests

Abstract: An interface between compacted soil and a structure is commonly encountered in various geotechnical engineering projects, e.g., soil nails, retaining walls, shallow foundations, pile foundations, and so on. The interface strength depends on the way the soil-structure interface is formed. A cast-in-situ interface is very common in many geotechnical projects. This kind of interface is formed by placing concrete/cement grout over the prepared soil surface. The cement part can be formed over a prepared soil surface in two ways: (1) by normal gravity grouting and (2) by pressure grouting. In this study, a series of interface direct-shear tests was performed between compacted, completely decomposed granite (CDG) soil and cement grout under saturated conditions with different grouting pressures and normal stresses. The behaviors of the shear-stress–displacement curves of the soil-cement interface are similar to those of CDG soil. Grouting pressure and normal stress have influence on the behavior of the s...

Influence of Soil Reinforcement on Horizontal Displacement of MSE Wall

Abstract: Mechanically stabilized earth(MSE) walls offer simpleconstructiontechniques,pleasing aesthetics,and cost-effectivesolutions as an alternative to conventional gravity walls. However, design and construction should be carefully evaluated to achieve satisfactory perfor- mance of the wall. A case study is presented on a MSE wall located on State Highway 342 in Lancaster, Texas. The horizontal movement of the MSE wall was between 300 and 450 mm within 5 years of construction. A forensic investigation was performed to determine the causes of the excessive movement. It was identified that inadequate reinforcement length was one of the contributing factors that caused horizontal displacement of the MSE wall. The objective of this study was to determine the effects of soil reinforcement on excessive movement of the MSE wall. As a part of the forensic investigation, two inclinometers were installed at the site to monitor any additional movement of the MSE wall. The inclinometer results suggested that the wall continued to move at an average rate of 4.5 mm/month during the investigation period. A finite-element (FE) program was used to simulate horizontal displacement and stability of the MSE wall. It was observed that the numerical modeling results were in good agreement with inclinometer results. A parametric study was conducted to identify the effects of soil reinforcement on horizontal movement at varied wall heights and backfill conditions. Numerical analyses results indicated that the effect of reinforcement stiffness was not significant at a wall height of 4 m compared with 8 and 12 m. The wall movement varied from 74 to 29 mm for an increase in reinforcement stiffness from 250 to 42,000kN= ma t 1:0H reinforcement length. The variations in displacement with reinforcementlengthssuggestedthatsubstantialreductionindisplacementoccurredforanincreaseinlength-height(L=H)ratiofrom0.5to0.7. FEmodelingresultswereusedforsensitivityanalysisemployingastatisticalanalysisprogram.Basedontheanalyses,reinforcementlengthand stiffness wereidentified as influential factors for thehorizontal displacement of MSE walls at a specific height.DOI:10.1061/(ASCE)GM.1943- 5622.0000297. © 2014 American Society of Civil Engineers.

Expanded Polystyrene-Based Geomaterial with Fly Ash

Abstract: This paper reports the engineering behavior of proposed expanded polystyrene-based geomaterial (EPGM) with fly ash through a laboratory experimental study. The proposed geomaterial is prepared by blending fly ash with expanded polystyrene (EPS) beads and a binder such as cement. The effects of different compositions and different mix ratios between EPS beads and fly ash (0.5–2.5%), cement and fly ash (10–20%), and water and fly ash (50 and 60%) on density, compressive strength, and initial tangent modulus of the geomaterial formed are studied. The authors observe that the density of EPGM can be effectively controlled by the quantity of EPS beads added in making the material. With the inclusion of merely 0.5–2.5% of EPS beads to fly ash (by weight), the density of the geomaterial formed can be reduced from 1,320 to 725 kg/m3. The compressive strength of EPGM increases considerably if cement-to-fly ash ratios of 10, 15, and 20% are used. Compared with EPS block geofoam, EPS beads mixed geomaterial h...

Application of an Artificial Neural Network for Modeling the Mechanical Behavior of Carbonate Soils

Abstract: Carbonate soils have some distinctive features such as compressibility and skeletal particle crushability that make them distinguishable from other types of soils. Many experimental models have been developed to describe the complex behavior of carbonate soils, but despite these numerous works, there is no unified approach that can model the behavior of various types of these soils. In this paper, a new approach based on artificial neural networks is presented to predict the mechanical behavior of different carbonate soils. The network had five input neurons, namely, relative density, axial strain, maximum void ratio, calcium carbonate content, and confining pressure; ten neurons in the hidden layer; and two neurons in the output layer, namely, deviatoric stress and volumetric strain at the end of each increment. The network was trained and tested using a database that included results from a comprehensive set of triaxial tests on three carbonate soils. Comparison of the model prediction and exper...

Prediction of Blast-Induced Vibration Parameters for Soil Sites

Abstract: In the recent past, the topic of blast loads on structures has received considerable attention from researchers. Site-specific empirical models for blast-induced vibration parameters like peak particle velocity (PPV), peak pressure (PP), peak particle displacement (PPD), and pore pressure ratio (PPR) are commonly used for blast-resistant designs. However, these empirical models do not consider the variation in soil properties, e.g., the degree of saturation and uncertain in situ conditions. Hence, in this paper, a total of 120 pieces of blast data from various soil sites have been collected and used to propose a generalized empirical model for estimating blast-induced vibration parameters by considering three basic soil properties, namely, unit weight, degree of saturation, and Young’s modulus. Standard errors and coefficients of correlation for the prediction of blast-induced vibration parameters by various empirical models are obtained with respect to the observed soil field data. The present em...

Novel Approach to Resilient Modulus Using Routine Subgrade Soil Properties

Abstract: Gene expression programming (GEP) models, a robust variant of genetic programming, are developed in this study to correlate resilient modulus with routine properties of subgrade soils and state of stress for pavement design applications. A database used for building the model was developed that contained grain size distribution, Atterberg limits, standard Proctor, unconfined compression, and resilient modulus results for 97 soils from 16 different counties in Oklahoma. Of these, 63 soils (development data set) are used in training, and the remaining 34 soils (evaluation data set) from two different counties are used in evaluation of the models developed. Two different correlations were developed using different combinations of the influencing parameters. The proposed constitutive models relate the resilient modulus of routine subgrade soils to moisture content w, dry density γd, plasticity index (PI), percent passing a No. 200 sieve (P200), unconfined compressive strength Uc, deviatoric stress σd,...

Lateral Earth Pressures Acting on Circular Retaining Walls

Abstract: The slip line method has been extended to consider the tangential stress and arbitrary magnitude of wall movement An analytical solution has also been proposed for the arbitrary mode of wall movement, and the soil mass behind the wall can be homogeneous or layered The mobilized internal friction angle of the soil and the soil-wall interface friction angle change with the movement of the wall; this has been widely accepted However, the development of them is not simultaneous The mobilized friction angles are used in the slip line method and the simplified slip line method to yield the nonlimit lateral earth pressure Results indicate that earth pressure decreases exponentially with increasing wall movement Comparisons of the calculated results with measured data and FEM results show that the present analytical method can provide good prediction of the lateral earth pressures and the limit wall movement equal to 03%H is appropriate in the calculation (where H is the excavation depth)

Formation of a Polymer Thin Wall Using the Level Set Method

Abstract: Considering foam’s expansive characteristics and using programming language, the level set method was used to simulate the polymer injection process that forms a thin wall; the influencing factors of the wall formation were studied for injection pressure, expansion ratio, and gel time. The polymer injection–wall-formation process was verified using a modeling test, and its molding effect was proven using a field test. The results show that the polymer injection technique can quickly form a thin wall, and it is feasible to use the level set method to simulate the polymer injection filling process and display the grout interface more accurately.

Estimation of Slope Stability Using Two-Parameter Criterion of Stability

Abstract: Modern methods for calculating slope stability in current finite-element programs involve the stepwise uniform reduction of the soil strength parameters. However, prediction of the strength-reduction law under the influence of external factors is not actually possible. The suggested method for safety-factor minimization will produce the most reliable estimation of slope stability. This idea is illustrated by calculating the safety factor for embankments composed of clay loam and sand.

Optimization of Design of Column-Reinforced Foundations

Abstract: The design of foundations on soft ground reinforced by columns usually involves two important verifications, namely, checking for adequate bearing capacity and checking for acceptable settlement performance. This paper details a comprehensive methodology for determining the optimized portion of the ground area that should be improved by the installation of columns. The optimization is required to avoid an overly conservative design and, consequently, the use of uneconomical quantities of material to construct the columnar reinforcement. The basis of the suggested methodology consists of first estimating the minimum improvement area ratio (IAR) required to ensure attainment of the required design bearing capacity of the reinforced soil and then determining an upper-bound or maximum value of IAR by considering the issue of allowable settlement. Optimization is then performed on the IAR within the range defined by these bearing capacity and settlement limits. Analysis of three case studies provides a...

Simplified Method for Calculating Active Earth Pressure on Rigid Retaining Walls Considering the Arching Effect under Translational Mode

Abstract: Based on the limit-equilibrium concept, a new method for calculating the active earth pressure acting on a rigid retaining wall that moves horizontally away from soil mass is proposed. Using this method, the trajectory of the minor principal stress resulting from the soil arching effect in retained soil mass is considered, and the arc-shaped axis of the minor principal stress is approximated to a linear axis using the improved horizontal flat-element method. The effects of soil’s internal frictional angle, its unit weight, the wall–soil friction angle relative to the active earth pressure, and the point of application of the resultant active earth pressure are investigated. Finally, the proposed method is applied to two existing tests for rigid retaining walls with different heights. A comparison of the predicted and measured values shows that the proposed method yields satisfactory results.

Simplified Mapping Rule for Bounding Surface Simulation of Complex Loading Paths in Granular Materials

Abstract: This paper presents a bounding surface plasticity model that can be used to simulate complex monotonic and cyclic loading paths. A new mapping rule that only uses the last stress reversal point is introduced to describe the stress-strain behavior of granular soils during loading and unloading. This mapping rule is easy to implement and is suitable for highly erratic cyclic loading conditions, e.g., those induced by earthquake or traffic loading. The application and performance of the model are demonstrated using the results of experimental tests with various stress paths conducted under both monotonic and cyclic loading conditions. The study shows the efficiency of the new mapping rule in capturing the characteristic features of the behavior of granular soils under various loading paths.

Field Tests on Deformation Property of Self-Weight Collapsible Loess with Large Thickness

Abstract: To study the deformation property of large-thickness self-weight collapsible loess and to understand the moisture migration law and matrix suction characteristics, a 40-m-diameter soaking test was conducted in the field with self-weight collapsible loess at a thickness of 36.5 m. The results showed that (1) the field collapse deformation law of the large-thickness self-weight collapsible loess varied in two periods, namely, the soaking period and the water cutoff period; (2) during the soaking test, the distribution of crack patterns appeared from local to overall, from near to far, and from dense to sparse, then gradually extended; (3) the volumetric moisture content changed in different soil locations; (4) suction developed steadily before soaking, whereas with a large amount of water, suction dropped steeply within a short time; and (5) the water content of soil above 20 to 25 m increased rapidly and soon reached saturation, whereas the water content of soil below that depth increased slowly an...