APPLICATION OF SMALL-THICKNESS CEMENT-MIXED SAND IN THE SUB-BASE COURSE AND ITS INFLUENCE ON THE VERTICAL PERMANENT DEFORMATION OF ROAD PAVEMENT

Abstract

The application of weak soils in the road pavement base leads to various settlements and instability that still need to be addressed. One common type of these settlements, which is a long-term serious concern for flexible pavements on weak soil, is permanent vertical deformation. In this research, a cyclic loading-testing model was developed to investigate the vertical permanent deformation behavior of pavements. Specifically, a typical road pavement consisting of a cement-mixed sand sub-base and a crushed stone varying base over a weak sand subgrade was investigated. The varying thicknesses of the base ranged from 0.10 m to 0.30 m, while the thickness of the cement-mixed soil subbase was 15 cm. The model pavement structure was constructed in a large testing tank measuring 1.0 x 1.0 x 0.8 m. A circular steel plate was subjected to cyclic trapezoidal load pulses to simulate traffic loading through an actuator assembly. Displacement transducers were employed at various positions and levels to monitor the pavement deformations. Three thousand cycles of cyclic load with varying loading stages ranging from 100 kPa to 550 kPa were applied. The experimental results revealed that applying a thin cement-mixed sand subbase on weak soil can reduce the pavement section’s permanent vertical deformation by 2 to 6 times, as well as reduce the vertical subgrade deformation by 3.62 to 44.1 times. Furthermore, it reduced the vertical stress at midspan by up to two times and did not show any negative effect on deformation, while reducing the thickness of the base course lying on the stabilized subbase from 30 cm to 10 cm.