基于盾构掘进效果的富水砾砂地层渣土改良试验研究

为解决土压平衡盾构在富水砾砂地层中掘进时螺旋输送机出口易发生喷涌的难题，依托昆明地铁4号线盾构隧道工程，开展富水砾砂地层渣土改良研究。首先通过大型渗透试验评价地层的渗透性，然后对试验段内每环的渣土进行坍落度试验，分析渣土改良对盾构掘进参数的影响，检验并评价渣土改良的实际效果，进而给出昆明地区富水砾砂地层的合理改良建议。研究结果表明： 1）昆明地区砾砂土的坍落度与含水率呈明显的正相关关系，而其渗透系数随测试时间的增加而降低，在2 h后减小为0； 2）塑流性较好的渣土对应着较低的刀盘转矩、推力和较高的掘进速度； 3）通过对掘进参数的分析可知，坍落度达到5~10 cm即可满足施工要求。

Research on Soil Conditioning of Water Rich Sandy GravelStrata Based on Shield Tunneling Effect

In earth pressure balance (EPB) shield tunnels in water rich sandy gravel strata, water is easily spewed from screw conveyors. Hence, a soil conditioning test is conducted on water rich sandy gravel strata based on the shield tunnel project of Kunming Metro Line 4. First, the soil permeability is evaluated by conducting a laboratory test. Second, a slump test is conducted on the site, and the effect of slump values on the tunneling parameters is analyzed. Finally, the surface subsidence is monitored to evaluate the effect of soil conditioning. Accordingly, guidance on soil conditioning of water rich sandy gravel strata in Kunming is presented. The following results are obtained. (1) There is a positive relationship between the slump value of sandy gravel strata in Kunming and its water content, and the permeability parameter decreases with time, attaining a value of zero after 2 h. (2) The cutterhead torque and thrust are small, and the tunneling speed is high in soils with a good plastic flow. (3) According to the analysis of the tunneling parameters, the slump of soil between 5 and 10 cm can satisfy the construction requirements for water rich sandy gravel strata.