Understanding of undrained shear behavior of cement admixed clay is of utmost importance for strength and deformation analyses in composite soft clay under short-term condition. From the critical analysis, the distinct difference in the responses of the same clay at uncemented and induced cemented states is brought out. The undrained shear behavior of uncemented clay is mainly dependent upon the clay fabric. The dismembering of the clay clusters in the fabric brings about the interlocking when the clay is in overconsolidated state. For the cement admixed clay, the clay is in meta-stable state. Hence, the strength and deformation characteristics are controlled by the clay fabric and cementation. The shear resistance is the sum of the shear resistance due to cementation \Iq\db\N and due to fabric \Iq\df\N. The term \Iq\db\N is practically constant with the increase in effective confining pressure at preyield state. The contribution from the clay fabric to the shear resistance \Iq\df\N comes into the picture at postyield state.

Undrained Shear Behavior of Cement Admixed Clay at High Water Content

A realistic assessment of the whole life cost of rail track foundations requires analysis of the effects of the repeated loadings applied by trains. This paper reports the effects of principal stress rotation (PSR) during cyclic loading on the permanent deformations measured in a series of hollow cylinder tests. The tests were carried out on a number of reconstituted soils selected in order to simulate foundation materials on an existing heavy haul railway line. Typical loadings and track geometry together with dynamic finite-element analyses were used to define representative stress changes to be applied to these soils, which were then tested with and without principal stress rotation during loading. It is shown that principal stress rotation has a significant and deleterious impact on permanent deformation of some materials. Therefore, it is concluded that cyclic triaxial testing, which cannot impose principal stress rotation, will not necessarily give good estimates of the long-term performance of rail track foundations. As PSR cannot be ignored when evaluating permanent displacements of rail track foundations, the use of more appropriate (realistic) testing methods such as the cyclic hollow cylinder or the cyclic simple shear apparatus is required.

Effects of Principal Stress Rotation on Permanent Deformation in Rail Track Foundations

The objective of this paper is to discuss the effect of grain shape and angularity on the undrained behaviour of sands. Four fine to medium (D50 = 0.15–0.29 mm) and uniform sands were examined. The...

Effect of grain shape and angularity on the undrained response of fine sands

Change in undrained shear strength characteristics of saturated remolded clay due to swelling

This paper presents the results of a detailed investigation into the ground deformations that occur under a railway line during the passage of a train. Four horizontal boreholes were installed at different depths below a ballasted railway track. Ground deformations were measured using geophones at set distances from the centreline of the track within each borehole. The results show vertical displacements reducing with depth, from a maximum at the sleeper. Sleeper displacements are dominated by pairs of bogies at the ends of adjacent wagons (which have a frequency of loading 1 Hz), although the effects of individual bogies (2 Hz) and axles (6 Hz) are also apparent. Higher loading frequencies attenuate with depth so that at a depth of 0·780 m below the sleeper soffit no axles are visible within the displacement data and by a depth of 1·98 m only the combined effect of pairs of adjacent bogies is apparent. In contrast, longitudinal horizontal motion is greatest at a depth of 0·78 m below the sleeper soffit, ...

Measurements of transient ground movements below a ballasted railway line

Formulation of a rational design methodology for laying or upgrading tracks for heavier and faster trains requires investigation of the effect of various track parameters on overall track responses...

Parametric study of resilient response of tracks with a sub-ballast layer

A rational method for design of railroad track foundation

Important geotechnical structures constructed on compacted cohesive soils often involve compaction either around or on the wet side of optimum water content. In general, at these water content values, water voids are continuous and air voids are occluded, and the soil may be assumed to be in a state termed as quasi-saturated. This paper evaluates the effective stress behavior of such quasi-saturated compacted specimens of Gangetic silt and Canyon dam clay in the broad framework of the conventional modified Cam-clay model. The initial state of quasi-saturated compacted specimens is shown to lie on the recompression line in w versus ln(p') space. The actual recompression line on which the specimen state would lie, and the corresponding equivalent past maximum pressure, are found to depend only on the amount of compaction energy and the soil structure, and are independent of the molding water content or initial dry density. It is observed that, at low effective confining stresses, quasi-saturated compacted soils behave like overconsolidated soils and the effective stress paths during undrained shear lie on the Hvorslev surface. However, at confining stresses greater than the past maximum pressure, these soils behave like normally consolidated soils and the effective stress paths move practically along the Roscoe surface toward the critical state line.

Effective stress behavior of quasi-saturated compacted cohesive soils. technical note

Transportation routes that are constructed on soft and problematic soils and subjected to heavy axle loads and traffic density give frequent maintenance problems. The subgrade soils on which formations are laid should be better accounted for during design and construction of transportation routes. For this purpose, there are two requirements. First, a simple but accurate test methodology simulating actual field conditions is needed. Second, data obtained from this test methodology should be properly correlated with observed changes in the field and with required design parameters. In this paper, a simple test methodology, consisting of undrained tests on unconfined cyclic and unconfined cyclic softened samples, is proposed for evaluating the behaviour of soils under transportation routes. The observed significant degradation of the subgrade soil under conditions when water is freely available and the mud-pumping problems encountered by railways have been explained by examining the softened state of test s...

A simple test methodology for soils under transportation routes

Important geotechnical structures constructed on compacted cohesive soils often involve compaction either around or on the wet side of optimum water content. In general, at these water content values, water voids are continuous and air voids are occluded, and the soil may be assumed to be in a state termed as “quasi-saturated.” This paper evaluates the effective stress behavior of such quasi-saturated compacted specimens of Gangetic silt and Canyon dam clay in the broad framework of the conventional modified Cam-clay model. The initial state of quasi-saturated compacted specimens is shown to lie on the recompression line in w versus ln (\ip′) space. The actual recompression line on which the specimen state would lie, and the corresponding equivalent past maximum pressure, are found to depend only on the amount of compaction energy and the soil structure, and are independent of the molding water content or initial dry density. It is observed that, at low effective confining stresses, quasi-saturated compacted soils behave like overconsolidated soils and the effective stress paths during undrained shear lie on the Hvorslev surface. However, at confining stresses greater than the past maximum pressure, these soils behave like normally consolidated soils and the effective stress paths move practically along the Roscoe surface toward the critical state line.

Yudhbir

Papers

Parametric study of resilient response of tracks with a sub-ballast layer

A rational method for design of railroad track foundation

Effective stress behavior of quasi-saturated compacted cohesive soils. technical note

A simple test methodology for soils under transportation routes

Effective stress behavior of quasi-saturated compacted cohesive soils