băng ghế dự bị một sàn bất thường dẫn đến chi phí vận hành cao cho tải và vận chuyển thiết bị. Tuy nhiên, quá nhiều phụ khoan có thể dẫn đến khoan không cần thiết Persistence nghĩa là mức độ dày đặc hoặc kích thước của một gián đoạn trong một chiếc máy bay. | 344 Civil engineering applications Figure Results of direct shear tests on sheet joints in the granite for Case Study II. mass would promote drainage. However during heavy precipitation events it was likely that high transient water pressures would develop and this was accounted for in design. It was assumed for design that water would accumulate in the tension crack to depth zw and that water forces would be generated both in the tension crack 7 and along the sliding plane U Figure . Earthquakes The site was located in seismically active area and it was assumed that the actual ground motions would be made up of both horizontal and vertical components that could be in phase. These ground motions were incorporated in the design by using both horizontal kH and vertical ky seismic coefficients as follows kH and ky X kH The seismic ground motions were incorporated into the slope design assuming that the acceleration would act as two pseudo-static forces. Stability analysis The nominal static factor of safety of individual blocks sliding on the sheet joints dipping at 25 Figure Cross-section of block used in design to model the assemblage of rock blocks in the slope for Case Study II. was about tan ộ tan Ỷp tan 36 tan 25 . However the shear movement along the sheet joints and the corresponding pattern of tension cracks behind the face shown in Figure indicated that under certain conditions the factor of safety diminished to approximately . Civil engineering applications 345 It was considered that the cause of the movement was a combination of water pressures and ice jacking on the joints seismic ground motions over geologic time and blast damage during construction. Also failure could have been progressive in which movement of one block would drag the adjacent block s and as movement occurred crushing of rock asperities along the sliding surfaces reduced the friction angle. The stability of the sliding blocks
