Abstract Abstract It is difficult to evaluate and predict the geostress state of a construction area if no sufficient relative documents are available. Geostress is measured in three boreholes using the hydraulic fracturing method at a hydropower station in Pakistan. The characteristics of shallow geostress are obtained, and deep geostress is predicted using a variation law of lateral pressure coefficients. The test results show that: geostress increases with the depth of overburden within a range of 123~346 m, with the maximum horizontal principal stress being 4.28~13.86 MPa, and the minimum horizontal principal stress being 3.02~8.19 MPa; and the horizontal principal stress reaches 40 MPa at the maximum depth, indicating that horizontal stress is dominant at the construction site. The stress state at the construction area is evaluated by using the strength-stress ratio and Hoek-Brown rockmass strength estimaton method. The results show that the geostress of the construction site is high; the predominant direction of the maximum horizontal principal stress is NEE, which is in agreement with that of previous research work; and the current tectonic stress of the construction site has a close relationship with the collision between the India and Eurasia plates. Based on the measured geostress and predicted geostress, it is determined that large deformation of surrounding rock will occur if the overburden exceeds 300 m, and severe squeezing-induced deformation will occur if the overbuden exceeds 800 m.
Abstract：
Abstract It is difficult to evaluate and predict the geostress state of a construction area if no sufficient relative documents are available. Geostress is measured in three boreholes using the hydraulic fracturing method at a hydropower station in Pakistan. The characteristics of shallow geostress are obtained, and deep geostress is predicted using a variation law of lateral pressure coefficients. The test results show that: geostress increases with the depth of overburden within a range of 123~346 m, with the maximum horizontal principal stress being 4.28~13.86 MPa, and the minimum horizontal principal stress being 3.02~8.19 MPa; and the horizontal principal stress reaches 40 MPa at the maximum depth, indicating that horizontal stress is dominant at the construction site. The stress state at the construction area is evaluated by using the strength-stress ratio and Hoek-Brown rockmass strength estimaton method. The results show that the geostress of the construction site is high; the predominant direction of the maximum horizontal principal stress is NEE, which is in agreement with that of previous research work; and the current tectonic stress of the construction site has a close relationship with the collision between the India and Eurasia plates. Based on the measured geostress and predicted geostress, it is determined that large deformation of surrounding rock will occur if the overburden exceeds 300 m, and severe squeezing-induced deformation will occur if the overbuden exceeds 800 m.
BAO Lin-Hai,
WANG Cheng-Hu,
GUO Qi-Liang etc
.Research on the Geostress State and Large-Rock Deformation of a Water Conveyance Tunnel in Pakistan[J] MODERN TUNNELLING TECHNOLOGY, 2015,V52(1): 38-44
2015, Vol. 52 