High geo-stress distribution and high geo-stress concentration area models for eastern margin of Qinghai-Tibet plateau

Abstract

High geo-stress and its engineering problems have severely affected the development of civil infrastructures in western China. The problems include high rock slope instabilities, rock burst, gas explosion and large-scale soft rock deformation in deep tunnels. This paper investigates the distribution of the high geo-stresses and the models of the stress concentration areas in the eastern margin of Qinghai-Tibet plateau so that a solid foundation can be formed to address the problems. The investigation is based on a comprehensive analysis of the previous research data of the eastern margin and uses remote sensing techniques, geophysics, geochemistry, and large scale geological surveying methods. The investigation has found that some special tectonic zones have high geo-stresses. The high geo-stresses are located at (1) the convergent boundary areas between two fault blocks with large strength differences, (2) the tectonic necks in front of active fault blocks, and (3) the intersection and/or termination areas of faults within the fault blocks. An example for (1) is the north Qilian high geo-stress area. Another example for (2) is the Minshan high geo-stress area in the northwest Sichuan. Furthermore, the investigation has summarized six basic models to characterize the high geo-stress concentration areas. The first one is the convergent stress concentration model at the boundary of two fault blocks. The other five stress concentration modes are oblique fissures or intersecting areas, areas without lower velocity layer in the crust, areas of compression induced tensile cracking, tectonic wedge areas, and tectonic neck areas, respectively.