Research On Macroscopic Deformation Properties Of Jointed Rock Masses And Its Engineering Application

Structural planes control the deformation and stability of the rock foundation, slope and underground caverns, which are the root of the complex mechanics properties of rock masses. Due to the intensive and uneven spatial distribution of fractures, the deformation characteristics of jointed rock masses show heterogeneity, anisotropy, scale effect and uncertain randomness strongly. In-depth research of the deformation properties of jointed rock masses is of great significance in theory and engineering practice, such as making the rock masses utilized fully and reinforcing them targeted.The key issue for evaluating the deformation properties is to obtain the equivalent deformation parameters. Lots of job have been produced by domestic and foreign scholars adopting different approaches, including empirical methods, in-situ tests, analytical methods and numerical experiments. However, limitations are still existed which can not meet the needs of great engineering practice as follows:(a) Analytical methods can well explain the deformation mechanism of regular and persistent joints, but can not provide reasonable simulation for non-penetrating joints; (b) Since modeling the 3-D rock discontinuity network is quite difficult, only a few explorations have been done based on the 3-D rock discontinuity networks and stochastic analyses of equivalent parameters are even more scarce; (c) Numerical experiments are the most operational and efficient way to explore the mechanical parameters of jointed rock masses, but there is a lack of reliability evaluation compared with in-situ tests; (d) Few researches have been conducted about the influence of deformation anisotropy on hydraulic structures, especially for the high arch-dam. To solve these issues, a series of studies on deformation mechanism of jointed rock masses have been carried out by combining with the above four methods. The main contents of the dissertation are as follows:(1) Research on the anisotropy deformation of jointed rock masses. Firstly, the equivalent elastic constitutive equation is proposed based on the principle of strain superposition. Anisotropy of kinds of simplified persistent joint sets are analyzed, which show that the deformation characteristics of the layered rock mass are symmetrical about normal direction of joints, the columnar jointed rock and the rock masses with three sets of orthogonal and continuous joints are symmetrical about flat. Then an accurate numerical simulation of non-penetrating joints has been done, which verifies that the rock bridge play an important role in shear resistance as pins. Lastly, in terms of four basic principles of strain superposition, stress consistency, stress sharing and strain consistency, the concept of influence of rock bridge is introduced, and the equivalent constitutive model is deduced systematically.(2) Research on the stochastic effect of deformation of jointed rock masses. In this thesis, the representative rock discontinuity networks are generated by using the Monte Carlo method, and a numerical testing method is developed to estimate the three-dimensional elastic compliance tensor based on the composite element method. Taking the jointed rock masses in the SW hydropower station as the research object, statistical analyses on each component of the elastic compliance matrix are carried out to explore the stochastic properties of jointed rock masses. As a result, different rock discontinuity network has different elastic compliance matrix, but the same components in different rock discontinuity networks are subject to a certain statistical law. The compliance tensor of weakly weathered jointed rock masses in the left bank of the SW hydropower station is closest to obey the lognormal distribution.(3) Back analysis of deformation parameters for joints from in-situ tests and prediction the compliance matrix of the regional rock masses. The numerical experiment based on the rock discontinuity networks is adopted to inverse the deformation parameters of joints, which taking normal stiffness and shear stiffness as the main control, combining the results of in-situ tests, geological surveys statistics and laboratory experiments. And these inversion results can be used to obtain the compliance tensor near the in-situ tests points and predict the parameters of the regional rock masses. The reliability of inversion results is verified by accurate numerical simulation of the rigid bearing plate test.(4) The numerical analysis model of the arch dam-foundation system considering multiple-scale structures. This model combines both implicit and explicit approachs, and it enables faults even stochastic joints can still be successfully simulated. The dam-foundation system of QBT hydropower station is studied to present the details of the process. From the analysis, a new recognition has been carried out. When the anisotropic characteristics caused by stochastic joints are considered, the displacement distribution of the arch dam and dam abutment rock will be changed. The river-along displacement of the dam abutment reduces and the angle between displacement vector and flow at the end of arch ring increases, which is beneficial to the stability condition of dam abutment. Nevertheless, the shape of the arch dam gets flattening and the stress condition turns worse, which should be paid attention to.The achievement obtained in this work may provide some references for studying deformation properties, obtaining rational parameters of jointed rock masses and evaluating the stability of hydraulic structure.