Abstract
The deformation of Muzhailing deep tunnel is about 2.3 m in the process of construction, which is difficult to be controlled by the traditional “anchor-grouting integration” support system. This paper deeply analyzes the geological characteristics, rock mechanics characteristics, and surrounding rock failure characteristics of Muzhailing tunnel. The deformation mechanism and the failure of the support system are analyzed through the numerical simulation, theoretical analysis, and field test. The authors propose support measures suitable for Muzhailing tunnel based on the analysis results. The maximum buried depth is 600 m, and the engineering rock mass at the depth has nonlinear physical and mechanical phenomenon. The maximum principal stress of Muzhailing tunnel is 25.7 MPa, which belongs to high-stress joint swelling soft rock tunnel. The NPR cable can achieve large deformation under the condition of constant support resistance. The authors put forward the coupling support mode of “NPR cable + steel arch frame + concrete,” which is based on the idea of transforming the composite deformation mechanism to a single type. The stress concentration appears in the range of 12 m in the surrounding rock circle, and the lateral and vertical stress distributions are relatively symmetrical after the improved support. The circumferential strain of the surrounding rock is greatly reduced, and the range of strain is reduced by 10%. The field monitoring results show that the new support system can well control the large soft rock deformation of Muzhailing tunnel (0.5 m). The support strategy proposed can effectively control the large deformation and promote the formation of new support concept for deep tunnel.
Highlights
With the rapid development of the world economy and society, tunnel engineering and underground engineering have set off a wave of great development
Zhang et al studied the stress field distribution and deformation law during the excavation of soft rock large deformation tunnels through theoretical analysis, numerical simulation, and field monitoring [17]. e results show that the short-step construction method can effectively control the deformation and plastic zone of surrounding rock. e effects of tunnel depth, tunnel diameter, and lateral pressure coefficient of original rock stress on the stress and deformation of surrounding rock of tunnel under the condition of sandstone are studied by means of finite difference software FLAC3D [18]
Sun thinks that the soft rock deformation support structure should have the characteristics of high flexibility and resistance increasing, so as to control the large deformation of tunnel [21]. e best range of soft rock tunnel surrounding rock support is within the loose zone of the tunnel. e large deformation can be well solved by bolting and shotcreting within the loose zone [22]
Summary
With the rapid development of the world economy and society, tunnel engineering and underground engineering have set off a wave of great development. Large deformation of weak surrounding rock leads to geological disasters, which brings about a series of Advances in Civil Engineering special problems to the design and construction of tunnels and other related underground projects [7,8,9,10,11,12] He et al divide the large deformation into the elastic large deformation and the plastic large deformation and divide the soft rock into the stress dilatancy type, the physical and chemical expansion type, and the structural deformation type, and they divide them into four grades according to the severity [13, 14]. An improved “NPR cable + steel arch frame + concrete” support mode is put forward, which can control the deformation of surrounding rock and get good effect
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