水布垭地下洞室燧石灰岩卸荷蠕变特性研究

Study on the Unloading Creep Properties of Strontium Limestone in Shuibuya Underground Cavern

为了解决水布垭水电站地下洞室发生不协调的卸荷蠕变破坏的问题,揭示分级卸荷对燧石灰岩蠕变特性的影响,在恒轴压分级卸围压的应力路径下,开展了燧石灰岩的三轴卸荷蠕变试验,研究结果表明:(1)在轴压恒定时,在分级卸荷条件下,燧石灰岩的轴向变形比侧向变形更明显;(2)随着分级卸荷量的减小,燧石灰岩发生蠕变破坏时的围压越小,燧石灰岩发生蠕变破坏需要的级数越多,同时需要的试验时间逐渐延长,分级卸荷量越小,燧石灰岩的蠕变应变越小;(3)在两种卸荷量应力路径下,侧向蠕变速率明显比轴向蠕变速率大,出现了明显的侧向扩容现象,而且加速阶段,出现蠕变速率陡然增大的现象;(4)在恒轴压分级卸荷应力路径下,燧石灰岩破坏形态主要以剪切破坏为主。

In order to solve the problem of uncoordinated unloading creep damage in the underground caverns of Shuibuya Hydropower Station,and to reveal the influence of staged unloading on the creep characteristics of strontium limestone,under the stress path of constant axial pressure staged unloading confining pressure,the triaxial unloading creep test of limestone was carried out.The research results shows that:(1)When the axial pressure is constant,under the condition of staged unloading,the axial deformation of strontium limestone is more obvious than the lateral deformation.(2)With the staged unloading,the smaller the confining pressure when the strontium limestone undergoes creep failure,the more stages are required for the creep failure of the strontium limestone,and the required test time gradually increases.The smaller the grading unloading amount,the creep strain is smaller.(3)Under the two stress paths of unloading amount,the lateral creep rate is obviously larger than the axial creep rate,and there is obvious lateral expansion phenomenon,and the creep rate appears in the acceleration stage.The phenomenon of abrupt increase.(4)Under the constant axial pressure step unloading stress path,the failure mode of flint limestone is mainly shear failure.