Study On The Current Crustal Stress Field In The Rockmass

Measurements demonstrate that the regional tectonic setting apparently does not control the features of the current crustal stress field, the direction of the major principal stress in the current crustal stress field is not consistent with the direction of the crushing stress regional tectonics borne during the last tectonic movement. The evolving degree of the regional geomorphology evidently affects on the features of the current crustal stress field. So the crustal stress fields change from the self-weight stress field to the horizontal stress field with the changing of the eroding degree of the regional geomorphology from valley area to hilly country to flat country.Depending on how the ground surface is denuded, the feature of the current crustal stress field and rock stress environment can be calculated analyzing the result in this paper: By analyzing the recovering feature of the elastic deformation of the rockmass in unload-stage under various pressures, it has been found there is close relationship between the recovering degree of the elastic deformation of the rockmass and the unloading degree of the pressure The direction of the major principal stress in the crustal stress field is not consistent with the direction of the crushing stress regional tectonics borne during the last tectonic movement.The evolving degree of the regional geomorphology evidently affects the current crustal stress field, which changes from the self-weight stress field to the horizontal stress field, with the changing of the eroding degree of the regional geomorphology ranging from valley area to hilly country to flat country.In valley area, where there is two stress belts, the bankslope stress belt and the self-weight stress belt within the mountain. The direction of the major principal stress is nearly parallel to the ground surface and inclines towards the valley in the bankslope stress belt. It is nearly vertical in the self-weight stress belt. According to the degree in which the original ground surface has been denuded, the magnitude and the angle of inclination of the major principal stress can be calculated (such as the magnitude of the intermediate principal stress). In hilly country and flat country, the direction of the major principal stress is nearly horizontal and parallel to the orientation of the major axis of the basin or the flowing direction of the regional eroding river nearby. The magnitude of the major principal stress can be calculated, according to the degree in which the original ground surface is denuded.On the whole, the results of studying the characteristics of the current crustal stress field and rock stress environment according to the regional geomorphology features are consistent with the results of stress measurement, are helpful for designing underground powerhouses and pressure tunnel of large-scale hydroelectric projects.