压力水作用下硬石膏岩膨胀性研究

Influence of pressured water on the swelling of anhydrite rock

针对隧道工程中硬石膏围岩在压力水作用下的膨胀现象,设计加工了多功能膨胀仪。使用该仪器及MTS815岩石力学测试系统,对不同水压条件下硬石膏岩的轴向膨胀应变及侧向膨胀应力进行了测试,对压力水作用后硬石膏岩的含水状态及力学特性进行了测试。结果表明:水压越大,硬石膏岩的最大轴向膨胀应变及最大侧向膨胀应力越大,膨胀起始时间越短;随水压的增大,硬石膏岩的吸水率增大,结晶水率逐渐增大并趋于吸水率,而自由水率逐渐减小并趋于0;硬石膏岩的弹性模量和峰值强度随水压的增大而增大。这些说明水压能影响其含水状态,增强硬石膏岩的膨胀性,促进其膨胀的激活,提高其力学性能。基于试验结果,建立了压力水作用下的硬石膏岩吸水状态方程,并改进了湿度场理论体系中的膨胀本构模型。

With respect to the swelling of anhydrite rock surrounding the tunnel under the effect of pressured water, a multifunctional swelling test apparatus was designed and manufactured. Axial swelling strains and the lateral swelling stresses of anhydrite samples under different hydraulic pressures were tested by this test apparatus and the MTS815 rock mechanics testing system. Then the water-bearing state and mechanical performance of these samples were tested. The test results showed that when the hydraulic pressure became higher, the maximal axial swelling strain and lateral swelling stress became higher, meanwhile the activation time of swelling became shorter. With the increase of hydraulic pressure, water absorption by anhydrite increased, and the water in crystalline anhydrite phase gradually increased to maximum water absorption, while the free water gradually decreased and finally dropped to near zero. The elasticity modulus and peak strength increased with the increase of water hydraulic pressure. These indicated that the hydraulic pressure was able to increase the swelling behavior, promote the activation of swelling, influence the water conditions, and strengthen the mechanical performance. Based on the test results, the water absorption function with consideration of pressured water was established, and the swelling constitutive model in humidity stress field theory was improved.