Meshless Method On Seepage In Fractured Rock Mass In Xiaowan Dam Site With 3D Network Computational Simulating Technique For Random Discontinuous

Groundwater is commonly existed in the rock mass, The hydraulic head is a keyfactor in the bodily sliding-proof stability judgment. To ensure the safety of aconstruction project, and to conduct a good prediction of the effect that thegeo-environment acts on the project and the project reacts on the geo-environment,we should concern the distribution and the motion of the groundwater in rock mass.And we should have the model of the action and reaction between the groundwaterin the rock mass and the rock mass. In the factor coherent, we should have toknowthe seep way of the groundwater and the force on the rock mass aroused bythe groundwater, in order to judge the bodily sliding-proof stability with rockmechanics.Now, the conceptual models on groundwater flow in the fractured rock mass canbe classified as three basic types: 1. equivalent continuum models, 2. discretefractured network models, 3. conceptual frameworks. The discrete fracturednetwork models are based on the fracture network formed by the location, the dipand the shape of the fractures, and conduct the water head and the motioncharacters of the groundwater with the method of rock mass hydraulics. In the studyof groundwater in the fractured rock mass, some simplified discrete fracturednetwork models are used in the numerical simulation. Not all discontinuities areconsidered in these models. And in the traditional numerical simulation, e.g, DDA,FEM, UDEC, Flac, BEM, a mesh is needed. We can not set the simulation pointsfreely. So we can not use the regular mesh to describe an irregular system ofdiscontinuous. In these numerical simulations, the network is simplified, and thedescriptions of the discontinuous are not enough to get all the information neededfor the coupling calculating of the groundwater head and the stress in the rock mass.A new powerful method is needed.In recent years, the 3D network computational simulating technique for randomdiscontinuous has been developed efficiently. It can give us the distributing state ofthe random discontinuity in 3D space. The 3D network computational simulatingtechnique for random discontinuous provide us a reliable physical basis for study ofgroundwater in the fractured rock mass. The meshless method is based on anapproximation not on an interpolation. It is to calculate the points level by anapproximation with the points value in a compactly supported domain around it. Itis no need of any mesh, instead of that a set of points is needed. These points can beset freely and can be used to describe anything. These are advantages that the DDA,FEM, UDEC, Flac, BEM don't have. It is convenient to conduct a 3D simulationand heterogeneous simulation. These features are fit for conducting a discretefractured network models numerical simulation using the meshless method. In this paper, the fundamentals of various kinds of meshless methods areaddressed. These methods all have the feature of meshless, and are different in theconstruction of the approximation functions and the discrete ways of the governingequations. The advantage of the meshless method can be described as:1. In the numerical simulation of the meshless method, only points should be set and the locations and the parameters of the points should be known. So the 3D problem and the problem with complex structure can be solved by numerical simulation of the meshless method easily.2. The simulation functions are independence of the characters of any mesh, location, shape or the relationship between points and meshs.3. The coefficients matrix is sparse matrix and is banded. It is easy to solve the liner system of function.4. Any kind function can be used as the primary function, so the meshles method can solve any kinds problem. Now, several efficient meshless methods are developed. They have theiradvantages and disadvantages. These are from the differents in the construction ofthe approximation functions and the discrete ways of governing equations. In thesepaper, several kinds of the way to construct the approximation functions and todiscrete governing equations are discussed. Their features are addressed. And theadvantages and disadvantages of every kinds of meshless methods are discused byanalyzing their way to construct the approximation functions and to discretegoverning equations. Then a good way to construct the approximation functions anda good way to discrete governing equations which are fit for a discrete fracturednetwork models is used to form a MATLAB program. This is a new way forconstructing the meshless method. For a Lapalace equation, a meshless method of using the moving least squaremethod to construct the approximation functions and using the moving least squaremethod to discrete governing equations is fit. In this paper, this method is used toconstruct a numerical discrete fractured network models to simulate the water headand de seepage velocity. The way of discrete governing equations by the movingleast square method is improved in this paper, and the way to construct the primaryfunction and the way to construct the weight function are also improved. With the3D network computational simulating technique to form the discontinuous network,we get a 2D network of the crossing section of the 3D model and the meshlessmethod above to form a numerical simulation, a 2D practical numerical model ispresent. This model can calculate the water head and seepage velocity in fracturedrock mass efficiently. For practice, a way to set points should be developed. In thispaper, two schemes of setting points fit for numerical discrete fractured networkmodels are present. Set points both on the discontinuous and the rock, and setpoints only on the discontinuous. With example testing, the simulation in thesecond way can give a correct conclusion in 2D simulation. But the first simulationway will provide a widely usage. In this paper, several simple discontinuousnetworks are present as the examples to test the meshless method used. And apractical example in Xiaowan Dam Site is present as example too. With the testingresult, the meshless method using in the discrete fractured network model can givea correct distribution of water head and seepage velocity in the discontinuous. Sowe can get the pressure on the rock by the groundwater and can get the seepagepath. The main works in this paper: 1. Addressed several kinds of the meshless method, a meshless method of using the moving least square method to construct the approximation functions and using the moving least square method to discrete governing equations is conducted. 2. Improved the meshless method above for the fractured rock mass, and construct a new meshless method for the discrete fractured network model. 3. Improved the weight function, choused the single-order expression primary...