Interactions between water and rocks are the main factors affecting the deformation of rock masses on sloped banks by reservoir impoundment. The technology used in laboratory tests of water-rock interaction mechanisms cannot simulate the coupling of water, the rock structure and the initial stress environment. In this work, we develop an in situ hydromechanical true triaxial rock compression tester and apply it to investigate the coupling response of reservoir bank rocks to changing groundwater levels. The tester is composed of a sealed chamber, loader, reactor, and device for measuring deformation, which are all capable of withstanding high water pressures, and a high-precision servo controller. The maximum axial load, lateral load and water pressure are 12 000 kN, 3 000 kN and 3 MPa, respectively. The dimensions of the test specimens are 310 mm×310 mm×620 mm. The test specimens are grey-black basalts with well-developed cracks from the Xiluodu reservoir area. The results show that increasing water pressure promotes axial compression and lateral expansion, while decreasing water pressure causes axial expansion and lateral compression. A water pressure coefficient, K, is introduced as a measure of the hydromechanical coupling effect (expansion or compression) with changing groundwater level. A mechanical tester can be used to perform accurate field tests of the response of wet rocks to hydromechanical coupling. The test results provide new information about the deformation patterns of rock slopes in areas surrounding high dams and reservoirs.

Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

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