Engineering Behavior Of Cement-Soil-Fill Material Of High Speed Railway Subgrade

At present, development of high-speed railway demands a subgrade that possessessuch engineering properties as higher strength, greater rigidity, more stable and durable,lower strain and homogenous in longitudinal. Usually, subgrade-filling meets abovedemand cannot be easily obtained along the railway. Therefore, it's an effective method ofusing cement to improve the in-place filling and it has been applied in railwayconstruction, but construction quality of this kind of subgrate can't be easily controlledbecause of many factors. So it is important to develop a quick, simple and reliablenon-destructive method to explore the subgrade. To solve the problem, followingresearches have been done.First, a lot of laboratory experiments are made and the results show that main factorsaffecting the compression strength and elastic wave velocity of cement-soil are curing age,soil type, ratio of cement to soil and water content.Further, take into account these factors, correlation between elastic wave velocity andstrength is investigated. Results show that correlation between shear wave velocity andstrength is better than the one between longitudinal wave velocity and strength. As a result,it's more reliable if shear wave velocity is used to calculate the strength. The researchfinding supplies theory basis for non-destructive method.BP neural network model between elastic wave velocity, soil type, curing age andcompression strength, ratio of cement to soil of cement-soil is established. And this modelcan estimate engineering properties of cement-soil.Laboratory experiments are made to investigate the influence of environmentchanging to properties of cement-soil. The results show that if some large grained fillingsare added into the cement-soil, rigid skeleton will form in the cement-soil, which makesthe deformation in dry and humid environment and the influence to mechanical propertyof cement-soil decrease.