Abstract
The coefficient of tunnel broken zone combined with the max thickness is used to descript the loosening zone distribution after excavation, which defined to the ratio of broken zone area to tunnel cross section. With 16 operation modes designed by Orthogonal test, coefficient of the broken zone can be obtained with numerical methods. The findings suggest that the order of each factor is: surrounding rock grades, ratio of depth to span, side pressure coefficient, buried depth, span length. Gonghe tunnel of Yu-Xiang highway is used to introduce the basic flow of tunnel broken zone coefficient test. Results show that the broken zone coefficient is closely related to geological conditions and excavation methods and the scope of broken zone can effectively reduce by selecting suitable ratio of depth to span and excavation method.
Highlights
Influencing factors of tunnel loosening zone include three aspects, geological conditions, section structures and disturbance influence
Five influencing factors (Liu and Song, 2003; Jing et al, 1999; Zhao et al, 2004), surrounding rock grades (Wang et al, 2007), depth, span length, ratio of depth to span (Chen et al, 2011) and side pressure coefficient are considered in this study, with 16 operation modes designed by orthogonal test (Fang and Changxin, 2001), thickness and coefficient of the loosen zone can be obtained by numerical methods (Wu, 2005)
The findings suggest that the order of each factor is: surrounding rock grades, ratio of depth to span, side pressure coefficient, buried depth, span length
Summary
Influencing factors of tunnel loosening zone include three aspects, geological conditions, section structures and disturbance influence. Five influencing factors (Liu and Song, 2003; Jing et al, 1999; Zhao et al, 2004), surrounding rock grades (Wang et al, 2007), depth, span length, ratio of depth to span (Chen et al, 2011) and side pressure coefficient are considered in this study, with 16 operation modes designed by orthogonal test (Fang and Changxin, 2001), thickness and coefficient of the loosen zone can be obtained by numerical methods (Wu, 2005). Measurement data at home and abroad shows that, the Analysis of influence factors: Orthogonal test design: Five influencing factors, surrounding rock grades T, depth H, span length D, ratio of depth to span S1 and side pressure coefficient S2 are considered in this study. The surrounding rock is isotropic and homogeneous, section shape is Threecentered circular (Fig. 3), the boundary of model is 5 times bigger than the span length of tunnel, failure
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