Study On Traffic-load-induced Settlement Of Road On Soft Subsoil At Yellow River Delta

Because of land contradiction and the large subgrade settlement due to high embankment, the low-embankment is adopted for the high-grade highway design in the most domestic cities. The traffic-load-induced cumulated settlement of the soft subsoil is very serious when low embankment highway is constructed on soft subsoil. Yellow River Delta is widely distributed by sedimentary soil which contains low liquid-limit clay, sandy subclay, and silty soil, and these types of soil have poor engineering properties, some of which are under consolidated. The settlement of road on these types of soil is especially serious; however, this has not been studied yet. As Yellow River Delta economic development zone of ecological efficiency is carried out, the study on traffic-load-induced cumulated settlement is necessary.This project was comprehensively developed by laboratory and field tests and numerical and theoretical analyses. Designed traffic load simulation system was used to study the evolution and influence of cumulative settlement and pore pressure and residual stress and so on according to the frequency of traffic load. In this simulation system, the drop of the hammer can be adjusted to simulate the different traffic load. It was found that the traffic load has a great influence on the cumulative settlement of foundation soil. In addition, though the test on lime soil and preloading subsoil, it was found that these two methods can effectively decrease cumulated settlement of the soft subsoil.Chai-Miura Model was used to calculate and analyze the traffic-load-induced permanent deformation of Xinhe-Xinzhuangzi Highway on soft subsoil, in which traffic-load-induced dynamic stress was calculated through dynamic finite difference method. It was found that cumulated settlement development is fast in the initial phase, but as time increased, the deveolpment increase slowly. And cumulated settlement was very impotance to low embankment. When the embankment height was less than 1.5m, cumulated settlement decreased linearly with the increase of the embankment height. So from the point of view cumulated settlement,1.5m was the suggested maximum height of the low embankment. Traffic overload can induce serious cumulated settlement of road on the soft subsoil, so limiting overloaded vehicle is a effective method to reduce the cumulated settlement and to extend road life. Moreover, when the traffic load is less than 40kN, the traffic-load-induced cumulated settlement can be ignored and allowable in the engineering. Compared to cumulated settlement after 10 year, cumulated settlement after 0.1 years was 40 percent, and cumulated settlement after 1 year was 2/3, which declared early cumulated settlement had a large percentage in total cumulated settlement. Through analyzing the cumulated settlement corresponding to different embankemt height and traffic load, the functions on embankment height, traffic load, time and daily traffic volume were used to precisely fit the cumulated settlement. Finally, on account of the settlement-equivalence principle and the vehicle spectrum, the prediction method of cumulated settlement of road on soft subsoil was proposed.