Based on equivalent energy theory, the anisotropy damage constitutive model of jointed rock mass is set up with joint surface closing and friction considered, the flexibility tensor and its increments are deduced. The model is applied to analyze the stability of permanent high ship-lock slopes of Three Gorges, and the numerical results show that the model is fit for simulating damage evolution and progressive failure of surrounding rock mass of the project during excavation and support.
Joints not only have effect on mechanical properties and distribution of stress in rock mass, but also influence seepage trajectory and failure modes of rock mass. Damage evolution of joints depends on loading history and distribution of joints. Many simplified mechanical model have been set up to study mechanical properties of rock mass (Budiansky & O'Connell(1976), law & Broekenbrough (1987), Fanella & Krajoinovic (1988), Hudson (1983), Oda (1982)). But in these achievements, the influence of joint closing and joint surface friction still haven't been taken into consideration. In this paper, the anisotropy damage constitutive model is established with joint surface closing and joint friction considered.
The new established mechanical model of rock mass is applied to analyze the stability of surrounding rock mass of high ship lock slopes of Three Gorges. The rock mass at the flight lock area consists of amphibole plagioclase granites of ante Sinian System. The axial direction of the lock chamber segment of the permanent flight lock is 110"58' 08". Because some joint sets cross the lock chamber axis with a large angle. Only two joint sets with strike of NE-NEE(B) and NWW(A) are taken into consideration. The two sets have an average joint spacing of 1.2m and 1.85m respectively. The mechanical properties of the two sets are shown in table 2. 3. 1 In situ stress It is considered that initial horizontal stress is generally very low in the shallow and soft stratum because of stress relaxation effect, which is verified by in situ monitoring. Therefore, the initial stress in the completely, intensively weathered stratum is taken as that caused only by the dead weight. 3.2 Anchoring indexes Three kinds of anchoring method are designed in the slopes: systematic bolts, prestressed bolts and prestressed cables. The anchoring parameters are shown in table 3. 4. CONCLUSION New mechanical model with joint closing and friction considered is applied to analyze the stability of high ship lock slopes in three Gorges, and leads to some useful conclusion:
The new established model is fit for analysis stability and damage evolution of joints in hard rock during excavation and support.
With two joint sets considered in numerical simulation, the results show that some joints around excavation boundary are propagated. In general meaning, surrounding rock mass of ship lock slopes are stable.
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