西部白垩系富水基岩立井冻结压力实测研究

In-situ measurement and study of freezing pressure of shaft in western cretaceous water-rich bedrock

为了解决我国西部白垩系富水基岩冻结法凿井的技术难题,采用振弦式传感器对甘肃某矿风立井基岩冻结压力及界面温度进行实测分析,研究了凿井期白垩系基岩冻结压力的变化规律、成因及不均匀性等。结果表明：凿井期间冻结压力分为快速上升、急速增长、缓慢升高、趋于稳定4个阶段;在同一水平其具有明显的不均匀性,且影响因素较多;其最终稳定值达1.708~2.047MPa,小于西部基岩同深度最大理论经验值,也小于东部冲积层冻结压力上限值pω;两壁界面温度急速上升后快速降低,30 h内各点达最高温42.4~59.4℃,同一点处前后降温差高达51.86~71.3℃,极不利于冻结壁和井壁的安全稳定;沿用东部的设计方法和经验,导致井壁过厚,易因温度应力产生环向裂隙,故西部煤矿立井井壁结构设计和施工仍存在可优化空间。

To solve the technological problems of mine construction by freezing of cretaceous water-rich bedrock in western region, by using the vibrating wire sensors to measure and analyze bedrock＇s freezing pressure and interface temperature of air shaft in a Gansu mine, the change rules, causes and inhomogeneity on freezing pressure of cretaceous bedrock during shaft sinking have been studied. The results show that the freezing pressure contains four stages： rapid growth, dramatic increase, slow rise and gradual steadiness. It has obvious inhomogeneity at the same level and is caused by many factors. Its final stable value reaches 1.708-2.047 MPa, less than the maximal theoretical and empirical value of western bedrock at the same depth, and the upper limit of freezing pressure pω in eastern shock layer. The interface temperature of frozen wall and shaft lining rises sharply and then reduces quickly, with the maximum of each point reaching 42.4-59.4 ℃ within 30 h and the difference values 51.86-71.3 ℃after the temperature decrease, which is extremely unfavorable to the security and stability of the two wall. Following the eastern design methods and experiences tends to cause the wall to become much thicker and produce ringed temperature cracks because of temperature stress, so there still exists an optimized space on structural design and construction of the western mine shaft.