Numerical Test On Influence Of Weak Interbed On Underground Tunnel

According to a large number of underground engineering, stability of surrounding rock mass is dominantly controlled by weak interbed. In this paper, systematic numerical test have been carried out to study the stability of surrounding rock mass with different distribution of Weak interbed, different distance between weak interbed and limit of excavation, different thickness of weak interbed, in the different confining coefficient and representational surrounding rock mass graded II, III, IV. All of the numerical modeling is plain-strain type with elastic-plastic constitutive law and Mohor-Coulomb failure criterion, through the integrated numerical analysis program FINAL. Plentiful numerical test results have been drawn via analyse the deformation, tensile stress region, plastic region of surrounding rock and the stress status of shot-crete. All the results can be utilized by engineers, during the designing and construction. The main conclusions are listed as follows:(1) Based on the shortest line between weak interbed and limit of excavation and the location of point of intersection between limit of excavation, classification of Weak interbed distribution is set up, and the distance of distribution is defined; (2) According to the strength and deformation equivalent principle, influence zone of Weak interbed is introduced, and a new method to simulating the weak interbed with thickness is built; (3) Some quantificational results on influence of Weak interbed respectively at crown, right shoulder and right wall are summarized; (4) Some quantificational results on influence of Weak interbed with the distance between weak interbed and limit of excavation 0.2D, 0.5D, l.OD are gained; (5) Some quantificational results on influence of Weak interbed in the rock mass with confining coefficient 0.38, 1.0,1.5, 2.0, 3.0 are summed up; (6) Some quantificational results are summarized on influence of the underground surrounding rock mass stability with Weak interbed, in the representational surrounding rock mass graded II, III, IV; (7) According to the studying results some advices are suggested on designing of underground engineering.