Experimental study on the strength behavior of EHP

An improved soil-cement mixing pile construction method was developed to solve the issues such as uneven distribution of pile strength and poor pile quality obtained by using the traditional mixing-while-drilling method. Based on the new method, an Environmental-Friendly and Homogeneous Plastic (EHP) pile was formed following the procedure that cement-soil slurry mixture was blended outside the drilling hole before being mixing while drilling, which enables the operation to be controllable and adjustable. In this study, a series of unconfined compression tests were conducted on cement-soil samples prepared in the laboratory and field to evaluate the strength characteristics of EHP piles with various cement contents. The quantitative relationships between the unconfined compressive strength and different shapes were established. The strength reduction coefficient was employed to analyze the reduction in the unconfined compressive strength for in-situ EHP piles. Results indicate that the uniformity and strength of EHP plies are better than those constructed using the traditional construction technology. The improved construction technology can reinforce soft ground within greater depth. Compared with the samples made in laboratory and cured under standard conditions, a reduction in unconfined compressive strength of cement-soil mixing pile was found. The reduction coefficient R_P of strength was introduced to evaluate the reduction in the strength of EHP piles. Results show that the value of R_P decreases with the increasing cement content and R_P is in the range of (0.55, 0.75). Compared with the pile constructed using the traditional method, the reduction in unconfined compressive strength for EHP pile is relatively small, indicating a better bearing capacity.