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人为控制性放气是杭州地铁工程施工前防治浅层气地质灾害的必要措施。通过对浅层气藏形成中的水气运移过程分析可知,气藏原始包气带内的水压力和吸力沿厚度呈线性分布,孔隙水压力的大小与其相同位置处的静水压力相当;借助储层土体的室内土-水特征曲线并结合现场勘探资料,能够获得气藏初始饱和度分布。在分析有控放气措施下气藏内部水气运移基础上,利用GDS非饱和应力路径三轴系统地研究了气体释放过程中储气砂土的湿化变形,并给出了气体释放引起的含气地层沉降变形的预测方法。结果表明,在经历了形成过程中的自然脱湿后,储集层砂土被进一步压密,而工程放气措施引起的水浸或再吸湿过程中,单由饱和度或吸力减小所引起的砂土湿化变形量很小,可忽略其工程影响;有控放气措施下,由气体释放引起的浅层含气地层沉降沿气藏厚度自上而下依次递减,总沉降量约为气藏总厚度的1‰～5‰。
Man-made deflation is a necessary measure to prevent shallow gas geological disasters before the construction of Hangzhou Metro. Through the analysis of the process of water and gas migration during the formation of shallow gas reservoirs, it can be seen that the water pressure and suction in the original gas pack are linearly distributed along the thickness, and the pore water pressure is equal to the hydrostatic pressure at the same position. The soil-water characteristic curve of the reservoir soil combined with the field exploration data can obtain the initial saturation distribution of the gas reservoir. Based on the analysis of the water vapor transport inside the gas reservoir under controlled aeration, the wet deformation of the gas sands during gas release was studied by the three-axis GDS unsaturated stress path. The gas release was also given Prediction method of settlement deformation of gas-bearing strata. The results show that after natural desorption during formation, the reservoir sand is further compacted, while saturation or suction reduction is caused by flooding or reabsorption caused by engineering gassing measures Of the sand soil wet deformation is small, can ignore the impact of its project; controlled gassing measures, caused by the gas release of shallow gas-bearing strata from top to bottom down the thickness of the settlement, the total settlement is about The total thickness of the reservoir 1 ‰ ~ 5 ‰.