V. A. Sawant

Dynamic analysis of rigid pavement with vehicle–pavement interaction

Study of the dynamic response of pavements due to moving loads such as vehicles and aircraft has received significant attention in recent years because of its relevance to the design of pavements and airport runways. This paper presents an improved solution algorithm based on the finite-element method to analyse rigid pavements under moving vehicular or aircraft loads. The concrete pavement is discretised by thick plate elements that account for the transverse shear deformation and bending. The underlying soil medium is modelled by elastic spring and dashpot systems. The dynamic interaction between the moving load and the pavement is considered by modelling the vehicle by spring–dashpot unit. Graphical results are presented to demonstrate the significance of the dynamic interaction between the pavement and the vehicle on pavement response. Results indicated that slab thickness, soil modulus and velocity of aircraft had a significant effect on the response of the pavement.

3D Finite-Element Dynamic Analysis of Rigid Pavement Using Infinite Elements

A solution algorithm based on three-dimensional (3D) finite-element analysis is presented to study the dynamic response of concrete pavements subjected to moving loads. The pavement is discretized by 20-node isoparametric brick elements. The supporting soil medium is idealized by the elastic continuum model. Kelvin elements are attached to the transmitting boundary separating the near field and far field of the infinite soil medium in the vertical and longitudinal directions. Three-dimensional, 16-node infinite elements are attached to the transmitting boundary in the longitudinal direction to simulate the infinite soil medium in vehicle traverse direction. The moving vehicle is modeled by a mass supported by a linear spring and dashpot assembly simulating the vehicle suspension system. The vehicle-pavement interaction force is modeled with a Dirac-delta function. The dynamic equilibrium equation is solved by applying the Newmark-Beta integration scheme. The effects of vehicle-pavement interaction, pavement thickness, and soil parameters on the dynamic response of pavement are investigated by conducting a parametric study. It has been observed that the dynamic interaction between the moving load and the pavement has a significant effect on pavement response.

Experimental And Numerical Simulation Of Contaminant Transport Through Layered Soil

Abstract In this study, the solute transport through saturated multi-layer soils was studied in the laboratory using the soil column experiment. Sodium chloride was used as a conservative chemical and sodium fluoride as a reactive chemical in the experiment. During the experiment, a pulse-type boundary condition was used. An implicit finite-difference numerical analysis was also carried out to get the numerical solution of advective–dispersive transport including equilibrium sorption and first-order degradation constant for the multi-layered soil. The results of experimental breakthrough curves (BTCs) showed that the order in which the soil layers were stratified in a water-saturated profile did not influence the effluent solute concentration distribution. The results also show the effect of column Peclet number, retardation factor, and first-order degradation coefficient on BTCs for the solute transport in multi-layered soils.

Numerical and Experimental Investigations of Granular Anchor Piles in Loose Sandy Soil Subjected to Uplift Loading

AbstractThe granular anchor pile (GAP) system is one of the relatively new innovative ground-improvement techniques used to sustain the tensile loads. This paper presents the behavior of a GAP system in a loose sandy soil. The small-scale laboratory tests were conducted on a loose dry sand to investigate the effect of embedded length of pile on the uplift capacity of the GAP system. The results were compared with the numerical analysis using a three-dimesional finite-element analysis software. In the detailed numerical study, the effects of key parameters, such as length (L) and diameter (D) of pile and the elastic modulus of surrounding soil, on the uplift capacity of the GAP were examined. The load-displacement response of the GAP was also analyzed and is reported in this paper. For a constant diameter of the GAP, its ultimate uplift capacity increases as the L/D ratio increases. However, for L/D ratios greater than 10, further increase in the L/D ratio does not contribute to the load sharing significan...

Effect of Edge Distance from the Slope Crest on the Response of a Laterally Loaded Pile in Sloping Ground

Abstract Compared to the field tests, the numerical modelling is an economical way to analyze the response of laterally loaded piles in sloping grounds. This paper presents a three-dimensional finite element analysis to investigate the effect of edge distance from the slope crest of a laterally loaded pile embedded in the sloping ground for different slope angles and pile lengths. The results show that the pile top displacement and the bending moment in the pile decrease with an increase in the edge distance, whereas they increase as the slope angle is increased. The response of the pile in sloping ground is compared with its response in the level ground. The comparison is used to develop a simple methodology for estimating the pile top displacement and the maximum bending moment for any edge distance from the slope crest considering their values for level ground.

Finite element analysis of rigid pavement on a nonlinear two parameter foundation model

Abstract A numerical iterative procedure based on finite element method has been presented for analyzing the dynamic response of pavement to moving load resting on a nonlinear subgrade. The pavement is descretized by finite and infinite beam elements. The foundation is modeled by Pasternaks two parameter soil medium. The nonlinear stress-strain relationship in the soil is considered. The dynamic vehicle-pavement interaction (VPI) effects are incorporated in the analysis. The effect of the material nonlinearity of the supporting soil medium on the pavement response is investigated by conducting a parametric study.

Effects of fines on compaction characteristics of poorly graded sands

Abstract For preliminary design and assessment, various researchers have correlated the compaction characteristics with different soil properties. In this study, an effort is made to correlate the compaction characteristics of poorly graded sand with the percentage of fines present in it. Plastic and non plastic fines are added to poorly graded sands in varying quantities and the changes in maximum dry unit weight and optimum moisture content are studied. It has been found from the studies that the addition of fines up to a certain amount increases the maximum dry unit weight of poorly graded sands and the amount of increase depends on the uniformity coefficient value of the sand.

Dynamic Pavement-Vehicle Interaction of Rigid Pavement Resting on Two-Parameter Soil Medium

An improved solution algorithm based on Finite Element Method is adopted to analyze rigid pavements under moving vehicular or aircraft loads. Analysis is based on the classical theory of thick plates resting on two-parameter elastic soil medium. The pavement is discretized by four node thick plate elements that account for the transverse shear deformation and bending. The underlying soil medium is modeled by Pasternak shear layer and linear elastic spring and dashpot systems. The dynamic interaction between the moving load and the pavement is considered by modeling the vehicle by spring-dashpot unit. The pavement-vehicle interaction force is modeled with Dirac-delta function. It has been observed that the dynamic interaction between the moving load and the pavement has significant effect on pavement response.

Insight into pile set-up and load carrying capacity of driven piles

Abstract Pile set-up and pile relaxation refer to the time dependent increase and decrease in the load carrying capacity of driven piles respectively. These two phenomena are governed mainly by the dissipation of excess pore pressure. In the case of pile set-up, the initially induced positive pore pressure within the soil mass becomes almost zero after some time, resulting in an increase in effective stress, whereas in the case of pile relaxation, the reduction of initially induced negative pore pressure causes a decrease in effective stress with time. For the safe and economical design of driven piles, a reliable prediction of the variation in pile capacity is essential. The researchers have tried to understand set-up and relaxation in the past, and attempted to predict the variation in pile capacity. This paper presents an insight into the pile set-up and the time dependent increase in load carrying capacity of driven piles along with some details of pile relaxation through a critical review of experimental and mathematical studies reported until recently. The review shows that the most studies are related to the set-up of driven piles because the driven piles are generally used in loose sandy and soft clayey grounds where set-up phenomenon is often observed. Some empirical relationships have been reported to predict set-up, and demonstrated reasonable success in a number of studies. A number of exploration phase field tests offering potential value in predicting set-up have been identified. A possibility of estimating pile set-up during design stage with the help of relevant subsurface exploration program is also discussed.

Effect of vehicle–pavement interaction on dynamic response of rigid pavements

In the present paper, dynamic response of rigid pavements subjected to moving vehicular loads is presented using an analytical procedure based on the finite element method. The vehicle–pavement interaction effects are taken into account while developing the solution algorithm. The concrete pavement is discretized by finite and infinite beam elements. Infinite elements are helpful in appropriate modeling of end conditions. The main purpose of the development of infinite elements is to model the unbounded domain. The underlying soil medium is modeled by Pasternak model which assumes the existence of shear interaction between the spring elements. The moving vehicle is represented by a mass supported by a spring-dashpot system. The vehicle -pavement interaction force is modeled with Dirac-delta function. Dynamic equilibrium equation is solved with Newmark-Beta integration scheme. It has been observed that the dynamic interaction between the moving load and the pavement has significant effect on pavement response. Parametric study is carried out to investigate the effect of vehicle–pavement interaction (VPI) and soil parameters on the response of pavement.