High Pressure Jet Grouting Method To Deal With Soft Foundation

With combination of actual examples of Xuan-Da Expressway and Jing-Qin Expressway this article gives a systematic illustration on the application of gyratory spray mud pumping (or high pressure sprayed pumping) during treatment for soft and subsided subgrade of expressways.The difference between the concept of weak subgrade and soft soil subgrade is presented. And the former is divided into three types according to formation causes, namely mountainous type, plain type and coastal type. Xuan-Da Expressway belongs to mountainous type and Jing-Qin Expressway belongs to plain type. Based on the engineering geological survey of these two expressways the physical dynamics character indices and the standard bearing forces of each soil layers as well as the total settlement of the ground soil were determined and worked out. Studies show that subgrade bearing forces of some sections from both expressways could not meet design requirement. The general settlement and difference settlement form greater hazards and need treatment.The characteristics of high pressure gyratory sprayed pumping discusses is presented, which is applicable in wide range of scope and ground layers, convenient for construction, long durability, wide source of materials. Mechanism for subgrade strengthening: complex foundation of cement solid and earth between piles was formed by pulsant load of flowing pressure and spraying flow, water wallop, cavitation phenomenon, water wedge effect, extrusion force and air flow agitation etc so as to enhance foundation bearing force and reduce settlement and deformation. Reliability: combined with actual examples of gyratory sprayed piles and complex foundation piles this chapter describes selection of gyratory sprayed pumping, scope, spraying materials, determination of gyratory spraying parameters, quality inspection and detailed construction process. Based on the results the article summarizes settlement laws through analysis of ground base settlement observation materials and this shows that after treatment ground base settlement was reduced greatly and the method is effective.Through a comparison between several treatment methods such as drainage consolidation, powder spraying, pressure mud pumping, gyratory spray pumping etc, the result shows that under suitable condition the application of gyratory spray pumping has some advantages such as short construction period, high ground base bearing force after treatment and less compressibility. It can guarantee structures to be built in due time and safety after completion. Those results show that gyrayory spray pumping technology has good practicality inengineering.