| Aimed at the problem of large deformation of chlorite schist under high groundpressure in Jinping II Hydropower Station, basic experiment, mechanical model andnumerical calculation are conducted. Meanwhile, the mechanical property of chloriteschist is further studied. In sum, innovative achievement and profitable acquirement areconcluded below:1. Shear test and traditional triaxial test are carried out on the completely saturated,completely dry and natural samples, the last of which would be sheared a second time.Several achievement is acquired from shear test that shear strength and shear stiffnessincrease with normal stress and they decrease with water content and the number offracture. The curves after peak and residual stress coefficient are also discussed. Fromtriaxial test of dried and saturated samples some points are obtained that peak strengthand Young’s modulus of dried samples are larger than those of the saturated. Chloriteschist is sensitive to confining pressure and it acts that larger peak strength, Young’smodulus together with softening coefficient are got when confining pressure is higher.2. Fluid flow test is carried on fractured and grouting fractured samples and resultshows that seepage discharge increases at the beginning and decreases linearly.However, seepage discharge of grouting fractured samples decreases in the exponentialform under confining pressure. In sum, confining pressure and grout play an importantrole on reducing rock permeability.3. Uniaxial compression test is carried on dried samples, samples in saturatedAlCl3solution, samples in saturated NaCl solution and saturated samples. Results showsthat compression strength and Young’ modulus rank in the form like: dried samples>samples in saturated AlCl3solution> samples in saturated NaCl solution> saturatedsamples. The history of electrical double layer is reviewed and the thickness ofelectrical double layer is given. Based on the theory above, the thickness of electricaldouble layer of samples under different condition is analysed. Mechanism of influenceon chlorite schist coupled by fluid-chemistry is worked out.4. Based on triaxial compression test, a new internal variable is definedconsidering the influence of stress state on plasticity evolution. According to test results,evolution characteristics of cohesion and friction angle is that cohesion decreases firstlyapproximately linearly and then parabolically, but friction angle always decreasesapproximately parabolically. Meanwhile based on test data, evolution of dilatancy angleis opposite to that of friction angle. Finally, mechanical model of chlorite schist isproposed with hardening-softening and dilatancy characteristics considered, andapplication to simulate the triaxial test shows a good agreement with the test data. Effortof this paper supply a rational mechanical model for engineering safety estimation andan important reference for the mechanical investigation of other similar soft rock.5. The excavation of assisted tunnel of chlorite schist in Jinping II Hydropower Station is simulated with FLAC3D. With excavation sequence, plasticity zone,displacement transformation and principle stress considered, advice is given toengineering construction. |
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