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Abstract In order to study the strength and deformation characteristics of the weak structural plane(zone) with high stress and high pore water pressure，a series of triaxial tests coupling water and rock for two weak structural planes(zones) from a large hydraulic engineering are realized on MTS815 Flex Test GT rock mechanics test system. The results show that：the variation of the intensity parameter f of the weak structural planes(zones) is very little following the change of pore water pressure，while strength parameter c decreases rapidly with the increase of pore water pressure，and with a pore water pressure more than 2 MPa，c can disappear entirely；the shear strength of the weak structural plane(zone) lessen with the increase of pore water pressure，and the shear strength of the weak structural plane(zone) with 4 MPa pore water pressure will be reduced by more than 30% under 10 MPa normal stress. The deformation properties of the weak structural plane(zone) weakened dramatically when pore water pressure increases，and the deformation modulus E of the weak structural plane(zone) with 4 MPa pore water pressure reduces 34.2% under 10 MPa confining pressure. The research results show that：we should consider the influence of pore water pressure after the completion of the project when we select the value of the mechanical characters of weak structural plane(zone) in rock. For general engineering，the shear strength of weak structural plane(zone) can be forecasted with effective stress principle；for large engineering with high water head，we should make it with the undisturbed sample test.
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Received: 16 April 2012
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2012, Vol. 31 
