STUDY OF WATER AND EARTH PRESSURE MODES ON SHIELD TUNNELS IN WATER-RICH DIORITE STRATA
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摘要: 迄今,在复杂的地质环境下,盾构隧道所受的水土压力尚难以精确计算。以济南地铁R2线为依托工程,选取2个代表性断面上实测的作用在衬砌结构上的水土压力,分析处于不同地质环境下掘进施工时盾构隧道管片水土压力的变化规律和分布特征。结果表明:1)在软硬不均的复合地层中,由于各土层物理力学性能的差异,盾构掘进约20环管片的距离后,测点处的水土压力才能基本稳定;2)对于正常固结的软黏土或粉质黏土,当覆土厚度大于2.5D(D为管片外径)时,已经产生土拱效应,采用Terzaghi松动土压力法计算较为合理。而对于覆土厚度小于1.5D的隧道来说,采用全土柱法较为合适;3)在上软下硬土层中,盾构隧道衬砌结构两侧的荷载并不对称,修正惯用法的荷载模式夸大了基底反力;4)不同埋深的两处断面的实测水压力值与理论静止水压力值基本相近。Abstract: In the complex geological environment, it is difficult to accurately calculate the water and earth pressure on shield tunnels. Based on the Jinan Metro line R2 as research basis, two representative sections were selected to measure the water and earth pressure on the lining structure, the evolution and distribution characteristics of water and earth pressure on the shield tunnel segments in different geological environments were analyzed. The results showed:1) In soft and hard nonuniform composite strata, due to differences in the physical and mechanical properties between strata, the water and earth pressure on measured sections would gradually kept it stable after being tunnelled about 20 shield segments away. 2) For normal consolidated soft clay or silty clay, when the thickness of the overlaying soil was greater than 2.5D (D was the outer diameter of the segmenting), the soil arching effect had already occurred, and the calculation method for loose earth pressure proposed by Terzaghi was more reasonable. For a tunnel with a thickness of less than 1.5D, the full soil column method was more appropriate.3) In a stratum with softer uppersoil and harder subsoil, the loads on both sides of the shield tunnel were asymmetrical, and the calculation mode of loads by the conventional correction method exaggerated the base reaction. 4) The measured water pressure on the two sections was generally close to the theoretical static water pressure.
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Key words:
- shield tunnel /
- complex stratum /
- field measurement /
- water and soil pressure
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