Soil Stress History Research Articles

Proposal for a New Classification of Common Inorganic Soils for Engineering Purposes

This study proposes a new soil classification based on the different behaviour of two fractions that can generally be distinguished in clayey soils: the “active, binder” fraction composed of clay minerals (conventionally constituted of particles less than 0.002 mm, termed clay fraction) and the “inert” fraction composed of non-clay mineral particles (greater than 0.002 mm). Apart from the soil stress history, the clay percentage (and the type of clay minerals it contains) is of primary importance for the mode of soil behaviour. Hence, inorganic soils are assigned into soil groups based on their clay percentages. Each group includes soils with similar intrinsic geotechnical properties. In describing the soil groups, the terms “grainy” and “fine” are used to distinguish soils with behaviour dominated by the characteristics of their granular and clay phase constituents, respectively. Between these, lie soils (semi-grainy and semi-fine) that are “transitional” between grainy and fine soils, with an intermediate behaviour determined by the increase in the clay fraction. Particularly for common inorganic soils with behaviour dominated by the clay phase, both the soil liquid limit and the clay percentage allow to estimate some soil properties such as the plasticity index, clay activity, intrinsic compressibility and residual shear angle.

Numerical evaluation of clay disturbance during blade penetration in the flat dilatometer test

This paper presents a study on the amplification of horizontal soil stresses during flat dilatometer test (DMT) blade penetration based on three-dimensional total and effective stress numerical analyses, while considering stress–flow coupling and large deformations. The focus here is on saturated clays, and the effect of soil stress history on the horizontal stress index is discussed in detail. The obtained results appear to be in good agreement with published and new field data, leading to the proposal of two new expressions for estimating the overconsolidation ratio and the earth pressure coefficient at rest directly from flat dilatometer tests in estuarine clays.

Effect of Soil Stress History on Scour Evaluation of Pile-Supported Bridges

AbstractScour is a major cause of bridge failures, and the Federal Highway Administration (FHWA) now mandates that states assess the susceptibility of their bridge inventory to scour. The authors have developed and described an integrated analysis program (IAP) that allows the user to accurately approximate nonlinear soil behavior around pile foundations within a structural analysis model. This paper describes a study performed to examine the influence of soil stress history on the outcome of a scour susceptibility analysis. Twenty-two models including the superstructure, substructure, and soil reactions were examined in which scour depth, soil type, and inclusion of soil stress history effects were varied. It was found that the stress history of soils had a limited effect on the performance of the bridge analyzed. This result was found to be in contrast to prior findings from studies performed on isolated piles, indicating that performing an integrated-type analysis is key to obtaining an accurate assess...

Measuring soil pressure within a soil mass

Reliable measurement of pressure within a particulate media has frustrated researchers in the field of soil mechanics and soil structure interaction for many years. The difficulty stems from the fact that most sensing systems involve compliance in the measurement concept. This compliance imparts a parasitic output to the measurement. In the past, researchers have attempted to calibrate this disturbance. Research has demonstrated that calibrations of this sort are dependent upon soil type, particle size, sensor geometry, and soil stiffness. Response of such sensors has been shown to be stress history–dependent: the response upon unloading may be highly nonlinear, resulting in a high degree of hysteresis. Complications in the measurement of soil pressure within a soil mass are significantly more complex from those met in the measurement of soil pressure at a structural boundary and must be considered separately. This paper utilizes a concept called the Null Soil Pressure System. Null pressure sensors were embedded and tested in a series of uniformly graded soils with particle diameters ranging from less than 0.15 to 15 mm. The data indicates that the response of the null pressure sensor consistently exceeds the actual soil pressure by a value of 4% ± 3%. This outcome is seen to be independent of soil type, particle size, stiffness, and stress history. No hysteresis is noted between loading and unloading, and additional loading cycles align with that of the virgin loading segment.

Determining Preconsolidation Pressure of the Lakeside New District Soft Clay of Hefei Based on Casagrande Method by Matlab

The preconsolidation pressure is an important index to determine the stress history of soil and also a major calculation parameter for the analysis of soil stratum’s deformation in the different stress history. Casagrade method is worldwide applied to determine the preconsolidation pressure. On the basis of research on consolidation test about the lakeside new district soft clay of Hefei by high pressure consolidation apparatus, and conformed to Casagrande method, the paper adopts quartic polynomial and least square method to fit the compression curve, and the preconsolidation pressure of the lakeside new distract soft clay of Hefei is determined by matlab software. The result provides reference for the calculation of foundation settlement considering stress history.

Study on Assessing Method of Stress History of Marine Soft Clay

The vane shear test (VST) is comprehensively analyzed by means of empirical method, which on soft ground of one offshore foundation engineering project in Jiangsu province of China. The methods of judgment of soil stress history are summarized. Based on the shear strength of soft clay, consolidation state of the soft clay is obtained. The conclusion shows that it belongs to slight over-consolidation state. In the meantime, the two evaluation methods are comparatively analyzed. In the depth more than 5 m, the curves of over consolidation ratio (OCR) of two methods show a good consistency. The methods and applications can provide useful reference for engineers.

Evaluation of K0 of Granular Soils using DMT Indices

A series of CPTs and DMTs are performed in the calibration chamber in order to develop methods that estimate the coefficient of at-rest earth pressure (K0), which is an indirect measure evaluating the stress history of granular soil. Among DMT indices and the qc value, KD is observed to be the most sensitive to the stress history while qc and ED show the similar trend of change as the vertical stress and stress history. The relation of Baldi et al. (1986) appears to be applicable for only NC sands as it does not include the term representing the effect of horizontal effective stress. The relations suggested in this study, KD/K0 = χ(ED/)δ and KD/K0 = a0(ED/pa)a1(/pa)a2, are observed to provide comparable accuracy in K0 values with those of Jamiolkowski and Robertson (1988) and Mayne (1995, 2001), regardless of the stress history. Suggested relations use only DMT indices while Jamiolkowski and Robertson (1988) require both CPT and DMT results, and Mayne (1995, 2001) needs both the CPT result and the OCR value. Although the adoption of OCR in Mayne (1995, 2001) offers a considerable improvement in the accuracy of the K0 value, it is not considered practical since the inclusion of both soil property (OCR) and index parameters in an empirical correlation provides excessive redundancy.

Using fracture grouting to lift structures in clayey sand

An inclined seven-story reinforced concrete building was leveled by a fracture grouting technique with quick-setting grout on a differential thickness of a clayey sand layer. The permeability and strength of clayey sand were controlled by clay content, although sand was the primary component of the foundation soil. The elevations of the building columns at basement level were closely monitored to record both the heaved volume of mat foundation after grouting and the settled volume during pore pressure dissipation. During the stabilizing stage of grouting, the foundation soil was densified by the repetitive fracturing process, which resulted in the lateral movement of the foundation soil. When the grout is less able to push soil laterally than upwards, the building starts to lift, the so-called lifting stage of grouting. The grouting efficiency is influenced by soil type, soil stress history, and foundation pressure. A final grouting efficiency of 27% and a linear relationship between grout use and percentage of elevation were obtained when this building was successfully and permanently leveled.

Dynamic behaviour of soils used for natural turf sports surfaces

The modulus and damping properties of soils in compression are a function of soil type, water content, stress history and loading rate. To model human–surface interaction with natural turf sports surfaces, stiffness and damping properties must be determined at dynamic loading rates. Two contrasting soil types, a Sand and a Clay Loam, commonly used in sports surfaces were loaded uniaxially to 2 kN at loading rates between 0.6 and 6 kN s−1 in modified dynamic soil testing apparatus. Soils were compacted prior to loading but initial cycles resulted in viscoplastic deformation, with strain accumulation with repeated cycles of loading. Ultimately a resilient, viscoelastic steady-state equilibrium with loading was established. Resilient modulus and damping ratio varied with soil type, water content, stress history and increased significantly with loading rate. The resilient modulus of the Sand soil, typical of modern free-draining sand construction natural turf sports surfaces, was significantly greater than that of a Clay Loam soil more characteristic of traditional natural turf surfaces; reducing water content caused an increase in modulus and a decrease in damping ratio in the Clay Loam soil. Determination of these properties provides initial data for the modelling natural turf surface behaviour in terms of both ball and human interactions, with further research required to determine the effect of both grass roots and leaves on mechanical behaviour.

Impact of hydraulic suction history on crack growth mechanics in soil

The mechanics of crack formation and the influence of soil stress history were described using the crack tip opening angle (CTOA) measured with fractography. Two soils were studied: a model soil consisting of 40% Ca‐bentonite and 60% fine silica sand and a remolded paddy soil with similar clay content and mineralogy. Fracture testing used deep‐notch bend specimens formed by molding soils at the liquid limit into rectangular bars, equilibrating to soil water suction ranging from 5 kPa to 50 kPa (with some 50 kPa specimens wetted to 5 kPa), and inserting a crack 0.4× specimen thickness. Bend tests at a constant displacement rate of 1 mm min−1 provided data on applied force and load point displacement. The growth and geometry of the cracks were quantified from a series of images to determine the CTOA. Modulus of rupture, evaluated from the peak force, increased as water suction increased. However, rewetting did not alter the peak stress from the 50 kPa value, indicating that shrinkage‐induced consolidation was more important than the soil water suction at the onset of testing. CTOA measured during stable crack growth decreased with drying. CTOA decreased even further when specimens equilibrated initially to 50 kPa were rewetted to 5 kPa. These results suggested that CTOA was primarily governed by the stiffness, although rewetting probably altered the capillary stresses in advance of the crack tip. Our future work will combine CTOA with a model that couples hydrological and mechanical processes to take into account the dependency of CTOA on the soil water regime so that crack propagation in soil can be predicted.

A study of critical state on an unsaturated silty soil

Critical state models for unsaturated soils have been proposed in recent years; however, the proposed models have been based on limited experimental data. Compacted specimens have generally been used for research, and the complications of soil fabric resulting from the compaction procedures have brought difficulties into the interpretation of fundamental soil behavior. There is a need to undertake further laboratory research studies on unsaturated soils, particularly to obtain a fundamental understanding of the shear strength and critical state of unsaturated soils by testing soil specimens with simple soil structures. Suction-controlled triaxial drained shear tests on an unsaturated silt were carried out as part of this research program. Specimens were prepared by gradually consolidating the initially slurried soil. The resulting specimens had a relatively simple soil fabric and stress history. The results showed that applying suction to an initially saturated specimen has a similar influence on the stress–strain behavior and critical state characteristics as does increasing its density by applying a higher confining pressure. The critical state lines for the unsaturated soil corresponding to different soil suctions are parallel to those for the saturated soil on the (q : p' ' ), (v : p' ' ), and (vw : p' ' ) planes.Key words: critical state, shear strength, unsaturated soils, volume change, triaxial testing.

Discussion: Influence of soil structure and stress history on the soil–water characteristics of a compacted till

Discussion: Influence of soil structure and stress history on the soil–water characteristics of a compacted till

Influence of soil structure and stress history on the soil–water characteristics of a compacted till

Influence of soil structure and stress history on the soil–water characteristics of a compacted till

Plasticity solutions for soil behaviour around contracting cavities and tunnels

The action of tunnel excavation reduces the in-situ stresses along the excavated circumference and can therefore be simulated by unloading of cavities from the in-situ stress state. Increasing evidence suggests that soil behavior in the plane perpendicular to the tunnel axis can be modelled reasonably by a contracting cylindrical cavity, while movements ahead of an advancing tunnel heading can be better predicted by spherical cavity contraction theory. In the past, solutions for unloading of cavities from in-situ stresses in cohesive-frictional soils have mainly concentrated on the small strain, cylindrical cavity model. Large strain spherical cavity contraction solutions with a non-associated Mohr–Coulomb model do not seem to be widely available for tunnel applications. Also, cavity unloading solutions in undrained clays have been developed only in terms of total stresses with a linear elastic-perfectly plastic soil model. The total stress analyses do not account for the effects of strain hardening/softening, variable soil stiffness, and soil stress history (OCR). The effect of these simplifying assumptions on the predicted soil behavior around tunnels is not known. In this paper, analytical and semi-analytical solutions are presented for unloading of both cylindrical and spherical cavities from in-situ state of stresses under both drained and undrained conditions. The non-associated Mohr-Coulomb model and various critical state theories are used respectively to describe the drained and undrained stress-strain behaviors of the soils. The analytical solutions presented in this paper are developed in terms of large strain formulations. These solutions can be used to serve two main purposes: (1) to provide models for predicting soil behavior around tunnels; (2) to provide valuable benchmark solutions for verifying various numerical methods involving both Mohr–Coulomb and critical state plasticity models. Copyright © 1999 John Wiley & Sons, Ltd.

The influence of soil structure and stress history on the soil–water characteristics of a compacted till

The soil–water characteristic defines the relationship between the soil suction and gravimetric water content, w, or the volumetric water content, θ, or the degree of saturation, S. Theoretical and empirical relationships are available to model the unsaturated soil properties such as the coefficient of permeability and shear strength using the soil–water characteristic and the conventional saturated soil properties. These procedures are attractive to engineering practitioners because rigorous laboratory tests on unsaturated soil are difficult and time-consuming and, therefore, costly. Various investigators generally have used the soil–water characteristic over a limited suction range (usually 0 to about 1500 kPa) to model the unsaturated soil behaviour. Soils, however, change from a saturated to a dry condition over a range of suctions from 0 to 1000 000 kPa. A rationale for extending the soil–water characteristic up to 1000 000 kPa is provided in this paper, and a method for estimating the residual state of saturation is presented. Soil–water characteristics were developed for the entire range of suctions from 0 to 1000 000 kPa on statically compacted clayey till specimens prepared at three different initial water contents. The influence of initial water content, soil structure and stress history, as it relates to the soil–water characteristic, has been studied and is reported in this paper. The initial water contents selected for this study represent the dry of optimum, optimum and wet of optimum conditions with corresponding densities determined from the standard AASHTO test. The results indicate that initial moulding water content has considerable influence on the resulting structure (and aggregation), which in turn influences the soil–water characteristics. In the low suction range (i.e. 0–1500 kPa), macrostructure governs the soil–water characteristics for specimens compacted with dry of optimum initial water contents and they exhibit a steeper slope. However, for the specimens compacted at wet of optimum, microstructure governs the soil–water characteristic behaviour. The soil–water characteristic of the specimens compacted at dry of optimum are influenced by the stress history; however, stress history appears to have no significant influence on the soil–water characteristics of the specimens compacted with wet of optimum conditions. The soil–water characteristic behaviour of specimens compacted with optimum initial water contents lies in between those of specimens compacted with water contents that are dry and wet of optimum. It appears that soil–water characteristics are not significantly influenced either by the soil structure (aggregation) or the stress history for the high suction ranges (i.e. 20 000–1 000 000 kPa).

Time effects on the stress-strain behaviour of natural soft clays

Laboratory tests on a wide variety of lightly overconsoli-dated natural clays show that important engineering properties such as undrained strength and preconsolidation pressure are time-dependent. Relaxation and step-changing procedures suggest that these properties decrease by 10–20% with a tenfold decrease in the speed of testing. The influence of strain rate on undrained shear strength appears to be independent of soil plasticity, test type or stress history during laboratory reconsolidation. Its influence on stress-compressibility curves from oedo-meter tests is independent of soil plasticity and test conditions. Ageing and delayed compression in clays produce a stiffer arrangement of the soil particles, and a quasi-preconsolidation pressure that is in part available for foundation design. The results from a series of conventional tests and stress-probe tests on two different clays show that yield envelopes in lightly overconsoli-dated natural clays are time-dependent, and contract in p&rime, q-space...

A Method for Estimating Foundation Ultimate Capacity

In the load testing of a foundation or any other ground structure, the method of defining ultimate failure load depends on many factors which include the design criteria and the soil stress history. Some of the more commonly used methods are noted in this technical note. A graphical method is presented which harmonises three of these methods and thus makes it easier to make comparable safety factors between different loading test results.

Friction Capacity of Piles Driven into Clay

Several studies on axial pile capacity in clays have shown that the average frictional resistance, expressed as a fraction of the average undrained shear strength or average effective overburden pressure, decreases with increasing pile penetration. Procedures to compute shaft friction are reviewed, and the effect of pile length on the development of shaft friction on piles in clay is examined in terms of the relative pile-soil stiffness and lateral pile movements during installation. Correlations are developed to relate shaft friction coefficients α,β,λ, to pile length, relative pile-soil stiffness, and soil stress history. Procedures are recommended to compute the friction capacity of piles in clay.

Overview of acoustic emission monitoring of rock structures

Overview of Acoustic Emission Monitoring of Rock Structures The acoustic emission technique for monitoring the stability of rock masses in mines was initiated in the late 1930's by Obert and Duvall in the U. S. A. and Hodgson in Canada. The technique, called microseismic monitoring at that time and even to the present, is currently being extended beyond mining into a wide variety of Civil Engineering oriented problems. These include: Monitoring of all types of stressed rock masses in addition to mines (the subject of this paper). Monitoring of a wide variety of soil masses (dams, embankments, foundations, etc.). Monitoring of seepage and grout flow in both rock and soil. Determining in-situ stress history of rock and soil. Monitoring of steel highway bridges and offshore platforms. Monitoring of concrete bridges, dams and buildings. Assessing stability of permanent and temporary anchors, wire rope and other components of larger structural systems. While most of these activities are still in some form of development, they are generally beyond feasibility and are in various stages of implementation. This paper describes the acoustic emission monitoring method as pertains to rock monitoring and some of the directions that equipment manufacturers are currently pursuing. It then briefly describes applications of the method in connection with the monitoring of rock structures.

Model tests on anchored walls retaining overconsolidated sands : Anderson, W F; Hanna, T H; Shah, S A Can Geotech J, V14, N2, May 1977, P214–222

This paperreports the findings of two series of tests which are part ofa continuing study into the behaviour of laboratory scale anchored retaining walls supporting cohesionless soil. In each test field construction was simulated and the behaviour of the wall, anchors, and soil was monitored. The behaviour of a wall supported by horizontal anchors has been examined as the overconsolidation ratio of the retained sand increases. The effect of anchor inclination has also been examined when the wall supports overconsolidated sand. The tests showed that the soil stress history had a very significant effect on the wall and retained sand behaviour.