The inversion methods of ground temperature field and ground temperature gradient field based on three-dimensional static heat conduction theory are presented with the influence from those minor factors such as heat convection and geology tectonics and so on. It can be used to simulate the three-dimensional ground temperature field in rock mass and to forecast the geothermal resources quantity of hot dry rock(HDR) on large scale. The paper analyzed the features and the mechanisms of ground temperature field and ground temperature gradient field of Rehai geothermal field in Tengchong，Yunnan province，China. Then the quantity of HDR geothermal resources was forecasted，and the results achieved from the presented simulation and forecast method of HDR geothermal resources of Rehai geothermal field can provide a reference to the geothermal exploitations.

According to the Carrol-Holt¢s hypothesis，the brittle porous material was simplified to be a hollow sphere. A three-dimensional discrete meso-element method (DEM3) developed in this laboratory is applied to simulate the process of void collapse for the brittle porous material with various pore volumes. The results show that the void collapse process can be successfully simulated and the conclusion is reached that the pore volume controls the process of void collapse. Since the real flaws in materials are mainly the pores and cracks，the investigations of brittle materials with various pores and cracks volume subjected to shock loading，whose total volume is 10.5%，are conducted to analyze the effects of pores and cracks on void collapse. It shows that the cracks decrease the critical pressure of void collapse，while the volume shrinkage results from the pore volume.