Consolidation Of Soft Soil Research Articles

Approach on the Engineering Properties of Lianyungang Marine Clay from Piezocone Penetration Tests

The use of the piezocone test (CPTU) in geotechnical site investigation offers direct field measurement on stratigraphy and soil behavior. Compared with some traditional investigation methods such as drilling, sampling, field inspecting method, or laboratory test procedures, CPTU can greatly accelerate the field work and thereby reduce corresponding operation cost. This article reviews previous interpretation methods of obtaining undrained shear strength, overconsolidation ratio, and coefficient of consolidation of soft soils from CPTU data, and introduces a new method, which the measured pore pressure into account. Piezocone tests with Vertek-Hogentogler CPTU truck have been complemented in a widely explored area in the soft marine deposit of Lianyungang City. Geotechnical design parameters (q t , f s , and u) obtained from CPTU and dissipation tests are evaluated for the marine clay in this area through methods based on cavity expansion (CE) and critical state (CS) theory proposed by Mayne, and compared with the result of vane shear tests and laboratory tests of undisturbed soil samples. Comparison of the results reveals the validity of CPTU tests to interpret the engineering properties of Lianyungang marine clay.

Response of multilayer geosynthetic-reinforced bed resting on soft soil with stone columns

In the present study, a mechanical model has been developed to study the behavior of multilayer geosynthetic-reinforced granular fill over stone column-reinforced soft soil. The granular fill and geosynthetic reinforcement layers have been idealized by Pasternak shear layer and rough elastic membranes, respectively. The Kelvin–Voight model has been used to represent the time-dependent behavior of saturated soft soil. The stone columns are idealized by stiffer springs and assumed to be linearly elastic. The nonlinear behavior of the soft soil and granular fill is considered. The effect of consolidation of soft soil due to inclusion of the stone columns on settlement response has also been included in the model. Plane strain conditions are considered for the loading and reinforced foundation soil system. An iterative finite difference scheme is applied for obtaining the solution and results are presented in nondimensional form. It has been observed that if the soft soil is improved with stone columns, the multilayer reinforcement system is less effective as compared to single layer reinforcement to reduce the total settlement as there is considerable reduction in the total settlement due to stone column itself. Multilayer reinforcement system is effective for reducing the total settlement when stone columns are not used. However, multilayer reinforcement system is effective to transfer the stress from soil to stone column. The differential settlement is also slightly reduced due to application of multiple geosynthetic layers as compared to the single layer reinforcement system.

The influence of anisotropic stiffness on the efficiency of vertical drains

The consolidation of soft soil is a well-studied problem in soil mechanics. Despite the availability of a large number of analytical solutions and FEM calculation techniques, not all relevant phenomena and their interactions are fully understood. This paper gives a short overview of relevant analytical solutions for the consolidation problem around a vertical drain and their characteristics. Next, a solution is presented incorporating anisotropy in stiffness. Cross-anisotropic stiffness clearly influences the hydrodynamic period. A significant retardation is found for Ev < Eh.The differences are explained by the various deformation patterns.

Nonlinear analytical solution for one-dimensional consolidation of soft soil under cyclic loading

This paper presents an analytical solution for one-dimensional consolidation of soft soil under some common types of cyclic loading such as trapezoidal cyclic loading, based on the assumptions proposed by Davis and Raymond (1965) that the decrease in permeability is proportional to the decrease in compressibility during the consolidation process of the soil and that the distribution of initial effective stress is constant with depth. It is verified by the existing analytical solutions in special cases. Using the solution obtained, some diagrams are prepared and the relevant consolidation behavior is investigated.

Mechanics of kinking and buckling of plastic board drains

The deformational response of plastic board drains installed to accelerate consolidation of soft soils, is examined as a problem of downdrag. The drain is modelled as a beam-column in which the axial load increases nonlinearly with depth. The soil response is represented by the Winkler medium whose coefficient of subgrade modulus increases linearly with depth. The governing equations for the drain-soil system are derived and solved as an eigenvalue problem. The critical buckling loads and the shape of the drain are obtained as functions of the normalized subgrade modulus of the soil at the top, the parameters signifying the variation of axial load along the length of the drain and the increase of subgrade modulus with depth. The derived deformed shapes of the drain are consistent with the observed ones.

Equivalent Diameter of Vertical Drains with an Oblong Cross Section

The availability of wick drains has rapidly led to their replacing conventional sand drains as a means of accelerating the consolidation of soft soils. Wick drains have an oblong shape, but the available theories of radial consolidation have been derived for drains having a circular shape. What is needed to apply these theories to the design of field installations of wick drains is a method of calculating the equivalent diameter of an oblong shape. Previous investigators have suggested several equations for computing the equivalent diameter of wick drains, but they yield different results. The equivalent diameter of oblong drains is determined with an analog field plotter. The results of all methods are reviewed and then compared to published experimental values of equivalent diameters of wick drains. These values were determined from laboratory consolidation tests. Values of equivalent drain diameters backfigured from field data are discussed with respect to the influence of smear.

Consolidation of soft soil by means of combined vacuum surcharge preloading : Ye, B R; Shang, S Z; Ding, G Q Proc International Conference on Geotechnical Engineering for Coastal Development, GEO-COAST'91, Yokahama, 3–6 September 1991P277–280. Publ Japan: Coastal Development Institute of Technology, 1991

Consolidation of soft soil by means of combined vacuum surcharge preloading : Ye, B R; Shang, S Z; Ding, G Q Proc International Conference on Geotechnical Engineering for Coastal Development, GEO-COAST'91, Yokahama, 3–6 September 1991P277–280. Publ Japan: Coastal Development Institute of Technology, 1991

Discussion: Self-weight consolidation of soft soils: an experimental and theoretical study

Discussion: Self-weight consolidation of soft soils: an experimental and theoretical study

Self-weight consolidation of soft soils: An experimental and theoretical study : Been, K; Sills, G C Geotechnique, V31, N4, Dec 1981, P519–535

Self-weight consolidation of soft soils: An experimental and theoretical study : Been, K; Sills, G C Geotechnique, V31, N4, Dec 1981, P519–535

Self-weight consolidation of soft soils: an experimental and theoretical study

Soil is laid down by sedimentation through water, passing through the phases of a fluid supported suspension, through a loose structure to a soft soil, the stiffness of which then gradually increases under additional load. Consolidation is caused by the self-weight of the soil and, while the sediment is soft, is accompanied by large strains. To predict magnitudes and rates of movement, the physical processes must be understood and used as the basis of a theoretical model. This Paper describes laboratory experiments on the development and consolidation of a soft soil in settling columns, with measurement of density (using an accurate, non-destructive X-ray technique), total stress, pore pressure and settlement. The results are compared with an earlier theoretical model. Modifications made to the model in the light of observed experimental features allow it to be used to predict the laboratory consolidation. Le sol est déposé par sédimentation à travers l'eau; il a d'abord la forme d'une suspension soutenue par un fluide, puis d'une structure sans cohésion et, enfin, d'un sol mou dont la rigidité s'accroit progressivement en fonction de la charge. La consolidation est entraînée par le poids intrinsèque du sol et, tant que le sédiment reste mou, ce processus de consolidation s'accompagne d'importantes déformations. Afin de pouvoir prédire l'ampleur et les taux de déplacement, il faut comprendre la nature des processus physiques qui ont lieu et en faire les base d'un modèle théorique. Le présent article décrit certaines expériences en laboratoire relatives à la formation et à la consolidation d'un sol mou dans des colonnes de sédimentation ainsi que les mesures de densité (à l'aide d'une technique faisant appel à des sondages précis par rayons X non destructifs), la contrainte globale, la pression interstitielle et la sédimentation. Les résultats sont comparés à ceux d'un modèle théorique précédent. Les modifications apportées au modèle en conséquence des phénomènes expérimentaux observés lui permettent de servir à prédire le processus de consolidation en laboratoire.