tailieunhanh - ELSEVIER GEO-ENGINEERING BOOK SERIES VOLUME 5 Part 8

Các sự kiện địa chấn kết thúc trong vỡ đá chỉ có 5% của tất cả các sự kiện được ghi lại và năng lượng địa chấn thứ tự của 105-108 1b ft. được phát hành trong vụ nổ. Nếu không, trong 95% còn lại trong các trường hợp, năng lượng phát hành là tâm điểm của sự thất bại bạo lực, tuyên truyền hướng tới khai quật có thể hấp thụ trong sự biến dạng của khu vực trước đây bị gãy của khối đá | 390 Tunnelling in weak rocks poor management condition affected tunnelling rate more adversely than poor rock mass condition. The third factor pertains to the breakdowns or hold ups during various operations in tunnelling cycle. These hold ups cause delays which are random in nature. Based on the data collected from many projects Chauhan 1982 proposed a classification for realistic assessment of rate of tunnelling presented in the following sections. CLASSIFICATION OF GROUND JOB CONDITIONS FOR RATE OF TUNNELLING The rate of tunnelling is seriously affected by the ground conditions. The factors under the ground condition affecting the rate of tunnelling are Terzaghi 1946 Bieniawski 1973 1974 Barton et al. 1974 . i Geology such as type of rock RQD joint system dip and strike of strata presence of major fault or thrust zones and their frequencies and type and rock mass properties ii Method of excavation including blast pattern and drilling arrangement iii Type of support system and its capacity iv Inflow of water v Presence of inflammable gases vi Size and shape of tunnel vii Construction adits whether horizontal or inclined their grade size and length and viii High temperature in very deep tunnels H 1000 m . On the basis of the above factors affecting the rate of tunnelling the ground conditions are classified into three categories - good fair and poor Table . It means that for the good ground conditions the rate of tunnelling will be higher and for the poor ground conditions the rate of tunnelling will be lower. The job ground conditions in Table are presented in order of their weightage to the rate of tunnelling. CLASSIFICATION OF MANAGEMENT CONDITIONS FOR RATE OF TUNNELLING The rate of tunnelling may vary in the same ground condition depending upon management quality. The factors affecting management conditions are i Overall job planning including selection of equipment and decision-making process ii Training of personnel iii Equipment .