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Mechanical properties of rock at high temperature are of importance for structure design and safety assessment in underground rock engineering. Brazilian disc test, axial compressive test and three-point bending test are adopted to determine the tensile strength σ t , uniaxial compressive strength σ c , elastic modulus E and ModeⅠ fracture toughness KⅠ C of sandstone at high temperature. Test results show that all of these values (σ t , σ c , E and KⅠ C ) are linearly increased with the increasing temperature below a certain temperature, 200 ℃ or 250 ℃, and decreased above this temperature. The linear equations are σ t =0.010 9T+2.322, σ c = 0.181 9T+63.138, E=0.004 9T+10.498 and KⅠ C =0.003 1T+0.60, respectively. Mineral compositions and microstructures of natural rock material have great influences on its mechanical properities at high temperature. Dominance of drying or microcracking would lead to the improvement or degradation of mechanical properities of rock.

Based on mineral component and in-situ vane shear strength of deep-sea sediment, four kinds of simulative soils were prepared by mixing different bentonites with water in order to find the best simulative soil for the deep-sea sediment collected from the Pacific C-C area. Shear creep characteristics of the simulative soil were studied by shear creep test and shear creep parameters were determined by Burgers creep model. Research results show that the shear creep curves of the simulative soil can be divided into transient creep, unstable creep and stable creep, where the unstable creep stage is very short due to its high water content. The shear creep parameters increase with compressive stress and change slightly or fluctuate to approach a constant value with shear stress, and thus average creep parameters under the same compressive stress are used as the creep parameters of the simulative soil. Traction of the deep-sea mining machine walking at a constant velocity can be calculated by the shear creep constitutive equation of the deep-sea simulative soil, which provides a theoretical basis for safe operation and optimal design of the deep-sea mining machine.

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