The use of synthetic fibres as reinforcement to stabilise expansive soils is gaining momentum. As a contribution towards this growing field of research two different types of synthetic fibres, Fiber Mesh® and Fiber Cast®, were evaluated as a stabilisation alternative for expansive soils in the presence of lime. California bearing ratio (CBR) is chosen as a performance indicator as it is a good pointer towards pavement effectiveness. Variables such as length and amount of the fibres as well as curing period were studied. Both deterministic and probabilistic (or reliability) analyses is presented in this paper. While the deterministic analysis helps in understanding the measured experimental data, the probabilistic approach accounts for the stochastic nature of the experimental data and provides a better rationale for the design methods. The deterministic approach showed that the improvement in CBR increased with higher fibre contents and longer lengths and the effect was prominent when lime was used as a stabiliser. There were some exceptions to this behaviour, which were noted in the paper. The probabilistic analysis showed that the amount and lengths of fibres were important factors in CBR strength. It was also determined that the variation in the target CBR value had a considerable effect on optimising the length and amount of the fibres.

In this paper, an approach for reliability-based design optimization of reinforced concrete cantilever retaining wall is described. A parametric study is conducted to assess the effect of uncertainties in design parameters on the probability of failure of cantilever retaining walls. In total, ten modes of failure are considered, viz. overturning of the wall about its toe, sliding of the wall on its base, eccentricity, bearing capacity failure below the base slab, and shear and moment failure in the toe slab, heel slab, and stem. The analysis is performed by treating backfill and foundation soil properties, geometric properties of wall, and reinforcement and concrete properties as random variables. These results are used to develop a set of reliability-based design charts for different coefficients of variation of friction angle of backfill soil (5 and 10%) and targeting reliability index ( βt ) in the range of 3–3.2 for all failure modes. A comparative study is also presented, which shows that optimized s...

This paper presents the use of pseudodynamic method to compute the rotational displacements of gravity retaining walls under passive condition when subjected to seismic loads. The concept of Newmark sliding block method for computing the rotational displacements under seismic condition and the limit equilibrium analysis have been combined in this paper to evaluate the performance of a gravity retaining walls under seismic conditions. One of the main features of the paper is the adoption of a new procedure to evaluate seismic passive earth pressure considering composite curved rupture surface (which is the combination of arc of a logarithmic spiral and straight line) and the dynamic nature of earthquake loading, which is useful to predict rotational displacements accurately. It also determines the threshold seismic acceleration coefficients for rotation using Newmark’s sliding block method. It is shown that the assumption of planar failure mechanism for rough soil-wall interfaces significantly overestimate...

In this paper, an analytical study considering the effect of uncertainties in the seismic analysis of geosynthetic-reinforced soil (GRS) walls is presented. Using limit equilibrium method and assuming sliding wedge failure mechanism, analysis is conducted to evaluate the external stability of GRS walls when subjected to earthquake loads. Target reliability based approach is used to estimate the probability of failure in three modes of failure, viz., sliding, bearing, and eccentricity failure. The properties of reinforced backfill, retained backfill, foundation soil, and geosynthetic reinforcement are treated as random variables. In addition, the uncertainties associated with horizontal seismic acceleration and surcharge load acting on the wall are considered. The optimum length of reinforcement needed to maintain the stability against three modes of failure by targeting various component and system reliability indices is obtained. Studies have also been made to study the influence of various parameters on...

This paper evaluates the effectiveness of stabilizing expansive soil with two different types of fibers, fiber mesh (FM) and fiber cast (FC), in conjunction with chemical stabilization. The intention of this study is to evaluate the effect of these fibers and lime in stabilizing expansive soil by improving its unconfined compressive strength (UCS) behavior. The effect of varying lengths (6 and 12 mm) and amounts (0.2, 0.4, and 0.6% dosage by weight of soil) of FC and FM fibers and varying curing periods (0, 7, 28, 60, 120, 180, and 360 days) on the UCS and on secant modulus of a semiarid expansive soil, in the presence of lime, was investigated. The main focus of this paper is on the determination of optimum fiber reinforcement parameters (in terms of fiber type, length, and dosage) for the stabilization of expansive soil in terms of UCS, which is of a prime importance in soil stabilization projects for practicing engineers. In deterministic optimization, the uncertainties associated with pavement system subgrade soil are not explicitly taken into account. Hence, resulting optimal solutions may lead to reduced pavement reliability levels. Therefore, this paper also focuses on determining the optimum amounts of reinforcement for desired UCS performance of lime-blended expansive soil using the target reliability approach (TRA). Experimental data were used to develop a parabolic model including factors such as length and dosage of fiber types to predict UCS as a response variable. In addition, it was concluded that TRA can be successfully employed in expansive soil stabilization applications to determine the optimum length and dosage of fiber reinforcements.