[This article belongs to Volume - 53, Issue - 05]
Gongcheng Kexue Yu Jishu/Advanced Engineering Science
Journal ID : AES-14-11-2021-91

Title : Centrifugal Model Test on the Influence Mechanism of Pipe Jacking Grouting Pressure on Formation Settlement
MA Xianfeng, ZOU Yuxiang, LI Xianghong, HONG Bin,

Abstract :

Pipe jacking synchronous grouting is an important method to reduce formation disturbance and final settlement. In order to obtain the relationship between the grouting pressure and the final settlement, find out the reasonable grouting pressure and grouting amount in the actual project to reduce the disturbance of the surrounding stratum, and provide theoretical and experimental supports for the improvements of the synchronous grouting technology, the stratum–mud interaction and the mechanism of settlement from the perspective of the structural characteristics of soil particles and bentonite molecules were analyzed, theoretical assumptions for the four stages of settlement were put forward. Then, the geotechnical engineering centrifuges and self-developed pipe jacking projects were used to simulate the pipe jacking under different grouting pressures on-site. Through the comparative analyses of the settlement curves, the conclusions of the theoretical analysis part were verified. Finally, the relevant parameters such as the grouting pressure in the experiment were applied to the pipe jacking project in Suzhou Donghui Park and the settlement measurement points were arranged on-site, further verified the conclusions. Researches showed that the settlement after grouting can be divided into four stages: soil collapse stage, seepage loss stage, mud skin formation stage and grout uplift stage. The soil collapse stage was short and the settlement speed was fast. Seepage loss stage lasted for a long time and the total settlement was large, which was the main part of the formation settlement. At the mud skin formation stage, the bentonite molecules accumulated on the mud–stratum contact surface to form mud skin, and the slurry was not permeated into the stratum and the settlement of the stratum slowed down. Finally, at the grout uplift stage, the grouting pressure of the mud acted on the mud skin to push the overlying soil and produce settlement compensation. The size of grouting pressure and grouting amount had a great influence on the final settlement. Small grouting pressure and grouting amount would increase the settlement caused by soil collapse and seepage loss, while large grouting pressure would cause excessive settlement compensation effect, even could cause surface uplift. Selecting a reasonable grouting pressure and grouting amount was very important and effective for controlling stratum settlement. It could be used in various pipe jacking projects on-site.