Effects of Jet Mixing on Adjacent Soils of an Excavation

摘要

Jet mixing is often used in soft ground to improve the stability of an excavation. However, the process of jetting and mixing may induce outward lateral displacement of the diaphragm wall, agitate pore water pressure and change the adjacent soil's properties. In this study, a basement excavation case in Taipei using the JMM technique was investigated. Besides regular instrumentation, additional inclinometers and piezometers were installed in the soil adjacent to the jet-mixed piles. In-situ and laboratory tests on the adjacent soils were also conducted both before and after the jetting. Results showed that: (1) Maximum lateral soil displacement recorded adjacent to the jet-mixed piles was about 65 mm. (2) Pore pressure in the adjacent soil showed drastic increase when the jetting was proceeded to the vicinity of the piezometer. (3) Jet-mixing also induced significant outward diaphragm wall displacement. Preloading the appropriate region of soils affected can simulate this effect.