高压沼气对浅部砂质粉土工程性质的影响

以长江口越江通道的盾构法施工隧道工程为背景 ,结合非饱和土双变量强度理论 ,研究在越江通道 (隧道 )施工过程中遇到的浅层 (砂性土层 )高压沼气地质灾害问题 .试验采用GDS系统 (geotechnicaldigitalsystems,岩土数字系统 ) ,进行非饱和土三轴试验 ,模拟含高压沼气地层中气体的分带特征与高压沼气释放后气压力的变化对土体强度的影响 ,以及沼气释放后破坏轴应力的变化 .实验结果表明砂性土土体强度随着气体压力的升高而升高 ,到达某一气压时 ,强度达到峰值 ,然后土体强度随气压升高而下降 ,土体具有很强的流动性 .同时研究了高压沼气从砂性土层中缓慢释放和强烈喷发这 2种形式对砂性土层结构和强度的影响

Research on Influence of High-pressure Marsh Gas on Sandy Silt Engineering

This paper researches geologic disaster of shallow strata (sandy soil strata) marsh gas of high pressure emerging in construction of Chongming tunnel through the Yangtze River using two-factor shear strength theory.Unsaturated soil tests with geotechnical digital systems are made to simulate store-in-zone characteristics of high-pressure marsh gas and influence of pressure change on soil strength as well as change of ultimate axial stress after gas releasing.The result of tests indicates that strength of the sandy soil increases with gas pressure rising and reaches ultimate strength with a certain gas pressure,then the soil strength reduces with gas pressure rising.Furthermore,soil with high-pressure marsh gas act as fluid.Influence on structure and strength of sandy soil aroused by slow gas releasing and intensive gas releasing is researched.