西宁至成都铁路某隧道高压CO_2气体研究及地质选线探析

Study on High Pressure Carbon Dioxide and Geological Alignment of a Tunnel on Xi′ning-Chengdu Railway

西宁至成都铁路定测阶段XCDCSZ-3-1号深孔突发高压CO_2气体,具有压力大、持续喷发时间长的特点。文章在收集和调查该区域地质背景的基础上,通过物探、钻探、气体取样、化验等综合勘察手段,研究了气体产生的原因、分布特征及运移、存储特征;在分析高压气体对工程影响的基础上,从地质角度研究其选线原则。结果表明:高压CO_2气体为无机成因,由基底大理岩受热分解产生,运移通道主要为古风化壳,主要聚集在基底鼻状隆起构造;高压CO_2气体分布与基底地层岩性、埋深、基底构造、盖层岩性、盖层断裂有着密切的联系,通过绕避其相关地质因素,可达到优化线路方案的目的。

Carbon dioxide gas,bursting in the deep drill hole of XCDCSZ-3-1 during the final survey of Xi′ning-Chengdu Railway,is characterized by high pressure and long duration of eruption.The genesis,distribution,migration and storage characteristics of CO2 gas were studied based on a survey of regional geological background and by means of comprehensive adoption of geophysical technology,drilling,gas sampling and chemical test.The alignment principles were also studied by analyzing effect of high pressure gas on tunnel in a perspective of geology.The results indicate that high pressure CO2 gas is of inorganic and caused by thermal decomposition of basal marble,the migration channel is mainly palaeo weathered crust which mainly accumulates in the snout-like bulging structure of baserock;distribution of high pressure CO2 gas is closely related to lithology,depth,structure of baserock,lithology of overlying strata and superficial fault,route scheme optimization can be achieved by bypassing relevant geological factors.