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Published on: November 20, 2014
Performance Analysis of Pipe-Jacking Waste Soils Solidified with Quick Lime and Fly Ash under Balanced Earth Pressure
Youjun Xu1,2, Zhenyu Li1,2, Zhigang Chen3
1School of Civil Engineering, Inner Mongolia University of Science and Technology, Baotou, Inner Mongolia 014010, China.
Abstract:
With its advantages of high cross-sectional utilization, shallow depth, and uninterrupted surface road traffic, the pipe-jacking method has been widely used in underground passages, metro stations, and other projects. However, this leads to a large volume of pipe-jacking waste soils that must be processed. Pipe-jacking waste soils are different from shield-tunneling waste soils. Therefore, it is not appropriate to simply use the same treatment method for shield-tunneling waste soils in the treatment of pipe-jacking waste soils. In this study, pipe-jacking waste soil samples were improved with 7% polyacrylamide (PAM) and 12% sodium-based bentonite solutions, with good performance being achieved. Based on this, quick lime and fly ash were used in the solidification of pipe-jacking waste soils, and experiments with different solution concentrations and solidification material additions were conducted, involving tests of compression, freeze-thaw cycling, wet-dry cycling, and microstructure. The results indicate that within the ranges of PAM and sodium-based bentonite addition ratios applied in this study, the solidification effects of quick lime and fly ash will not be significantly reduced during the improvement processes of pipe-jacking waste soils under balanced earth pressure conditions. Instead, it was found that there was an increase of up to 16% in the strength of pipe-jacking waste soils. Structural compactness can be primarily enhanced by gelatinous PAM, while sodium-based bentonite can promote the formation of hydrated colloids (such as C-S-H) and fill soil pores with hydrated gelatinous bentonite particles, thereby enhancing soil stability.
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