川西某水电工程气垫调压室原地应力及相关岩体特性参数的测量与应用分析

MEASUREMENTS AND APPLICATION OF IN-SITU STRESS AND RELATED ROCK MECHANICAL PARAMETERS OF SURROUNDING ROCK OF AIR-CUSHION SURGE TANK AT A HYDROELECTRIC PROJECT IN WEST SICHUAN

为论证某水电工程高压洞室的方案设计,采用水压致裂技术对高压洞室的原地应力及相关岩体力学参数进行细致的测试。测量结果表明,测点洞段围岩的最小主应力值为5.6～7.9 MPa,最小主应力状态为近水平;测点洞段围岩的抗劈裂强度一般为6.0～8.0 MPa,围岩自身具有较强的承载能力;在7.0 MPa高压下洞壁围岩的透水率大多小于1.0 Lu。因此,该洞段岩体具备较为理想的岩体力学特性,是修建高压力洞室的较好位置。但在规模庞大的高压洞室岩体内的极个别张性裂隙带,由于其承载能力弱,串通性强,高压下漏水严重,是无衬砌高压洞室工程建设的一大隐患。对此进行卓有成效的高压灌浆处理,显著提高围岩结构的完整性,增强其高压封闭功能,这是工程建设成败的关键。

In order to demonstrate the design scheme of the air-cushion surge tank for a hydroelectric project, the hydraulic fracturing technology is adopted to define the in-situ stress and related rock mechanical parameters of rock mass surrounding the high pressure cavern. The measurement results show that the minor principal stress in the rock mass around the high-pressure cavern is 5.6-7.9 MPa and nearly horizontal, the jacking strength is about 6.0-8.0 MPa, and the permeability under pressure of 7.0 MPa is less than 1.0 Lu. Therefore, the rock mass for the cavern is of good rock mechanical performance and a good pressure-cavern place. But there exist some tensile fissures in the rock mass of high-pressure cavern, which have poor bearing capacity, good connectivity and severe water permeability, and are a huge hidden trouble for the non-supported high-pressure cavern construction. The effective high-pressure grouting measures can improve the integrity of rock mass structures and enhance the high-pressure sealing function, which is the key for the construction of the project.