New Method for Shear Strength Determination of Unfilled, Unweathered Rock Joint

Rock Mechanics and Rock Engineering - Tập 48 - Trang 1515-1534 - 2014
Hyun-Sic Jang1, Bo-An Jang1
1Department of Geophysics, Kangwon National University, Chuncheon, Republic of Korea

Tóm tắt

Replicas were produced of 20 natural rock joints with different roughness. Factors affecting shear strength were examined and direct shear tests were performed using the replica joints to determine their quantitative shear strength characteristics. Results from the shear tests were best fitted by the power law equation, τ = Aσ n , where τ is the shear strength and σ n is the normal stress, and regression coefficients A and B were determined. The coefficient A (equal to τ when σ n is 1 MPa) is defined as the friction angle, and B, which determines the curvature of the plot of shear versus normal strength, is a factor that reduces the shear strength. The physical and mechanical properties of the coefficients A and B were defined, and the relationship between these coefficients and the factors affecting shear strength, such as roughness and joint wall strength, were analyzed quantitatively. A new equation, τ = σ n tan[ϕ b + ϕ J + s n], was suggested to measure and predict shear strength accurately based on results from these analyses, where ϕ b is the basic friction angle, ϕ J is the joint roughness angle, and s n is the shear component. Although the new shear strength equation is nonlinear, it is as simple to use as a linear equation and the shear strength can be estimated using only three easily measurable parameters (ϕ b , ϕ J , and σ j , the joint wall compressive strength). The failure envelope estimated using the new shear strength equation not only closely matches the measured shear strength, but also reflects the nonlinear relationship between the normal stress and shear strength.

Tài liệu tham khảo

Cottrell B (2009) Updates to the GG-shear strength criterion. Dissertation, University of Toronto

Cox BL, Wang JSY (1993) Fractal surfaces: measurement and applications in the earth sciences. Fractals 1:87–115

Fardin N, Jing L, Stephansson O (2001) Heterogeneity and anisotropy of roughness of rock joints. In: Sarkka P, Eloranta P (eds) Proceedings of the ISRM regional symposium, EUROCK 2001. Balkema, Espoo, pp 223–227

Hassani FP (1981) A study of the physical and mechanical properties of rocks and their discontinuities. Dissertation, University of Nottingham

Jang BA, Cho JS (1999) A study on shearing characteristics of joint model. J Eng Geol 9(1):69–82 (in Korean)

Jang HS, Kang SS, Jang BA (2014) Determination of joint roughness coefficients using roughness parameters. Rock Mech Rock Eng. doi:10.1007/s00603-013-0535-z

Kim DY, Lee HS (2009) Quantification of rock joint roughness and development of analyzing system. In: Kulatilake PHSW (ed) Proceedings of the international conference on rock joints and jointed rock masses. Tucson, paper 1019

Ladanyi B, Archambault G (1970) Simulation of shear behaviour of a jointed rock mass. In: Somerton WH (ed) Proceedings of the 11th symposium on rock mech. AIME, Berkeley, pp 105–125

Lee CH, Jeong GC (2002) Anisotropy of shear strength according to roughness in joint surface. J Eng Geol 12(4):421–437 (in Korean)

Patton FD (1966) Multiple modes of shear failure in rock and related material. Dissertation, University of Illinois