Dynamic Loading of Soil-Cement for Flexible Pavement Design
Stabilised soil-cement has been used in road pavements for considerable time. Certain design criteria concerning the properties of the material have been established. However, there is little knowledge of the material's behaviour under dynamic loading conditions simulating traffic loads. The aim of this research was to develop an understanding of the response of soil-cement to dynamic loading representing traffic stresses in compression, flexure, tension and tension-compression. Studies on the material have shown that a large number of factors affect the soil-cement properties. To obtain consistent results and to reduce the variables, pulverised Red Marl was used as the soil in this research. All specimens were prepared to constant density and moisture content, and cured at constant temperature and relative humidity. Variables such as cement content and curing time have been selected to study their effects on the static and fatigue characteristics of the soil-cement. Regression analyses were carried out on all results. Generalised relationships for parameters such as the unconfined compressive strength, stress-strain characteristics, Elastic and Dynamic Moduli have been developed for a wide range of cement contents and curing times as input variables for pavement design. Fatigue relationships in the form of number of load cycles to failure related to applied stress, based on experimental results, have also been developed for use as input for soil-cement pavement design. The static and dynamic flexure test results show a substantial drop in strength due to the fatigue effect in flexure. This is caused by the development of tension cracks at the underside of the beam specimen. The techniques of deformation measurement have been investigated, and a transducer system of high accuracy LVDT's developed. This system can meet most of the testing requirements such as reliability, accuracy at high frequency, ease of preparation and assembling. The finite element method was used to analyse three models of pavement structures. The Program for Automatic Finite Element Calculations (PAFEC) was used to predict the response of the layered pavement system and to quantify the traffic-induced displacements and stresses.
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