The Mechanism Research And Numerical Simulation Of Zonal Disintegration Of Surrounding Rock In Deep Tunnel

With the development of underground space， a series of new features inresponse to deep rock engineering which are different from shallow undergroundworkings were encountered. One of the new phenomenon is zonal disintegrationwhich has discovered in deep underground workings both at home and abroad. Zonaldisintegration means fractured zone divided by non-fractured zone(fractured zone-nonfractured zone-fractured zone). It has great theoretical significance andengineering practical value for deep engineering.Zonal disintegration exists in the deep engineering. This paper summarizes thebasic characteristics of the deep rock mass which is difference from shallow rockmass, and zonal disintegration phenomenon found in field observations andlaboratory simulation experiments is discussed; The applicability of strengthcriterion of deep rock mass is analyzed according to the characteristics of eachstrength criteria.The mechanism of zonal disintegration is studied by using the plane strainmodel, and the deep rock failure criterion is applied. It considers the excavation as adynamic process by building shape function of excavation unloading(cosinefunction). The trend function about radius is obtained by Laplace transform to theshape function of excavation unloading and motion equation; The mechanism ofzonal disintegration in deep rock mass is revealed considering the stress field ofrupture zone in deep rock after completion of the localization. The trend function ofrock displacement is used to calculate the radius and the width of the rupture zone inengineering examples，and the results is basically the same to the results when theexcavation unloading function is quadratic function. So the reasonableness isverified, when the excavation unloading function is cosine function.This paper bases on one of the diversion tunnel in Jin ping Hydropower Station,according to the actual engineering geological and hydro geological conditions. Theplane strain finite element model is built by ANSYS to analyze the zonaldisintegration according to the distribution of stress field and the plastic zone. Meanwhile, changing single parameter in the recalculate model, the sensitivity ofeach parameter can be analyzed according to the distribution law of plastic zone. Soit’s very useful to the design and the construction of tunnels in deep rock.At last, the idea of "Weak point strong support" and "differences support" israised according the mechanism of zonal disintegration of tunnels in deep rock. Tocontrol the deformation of surrounding rock, differences bolt support system isdesigned. And the effect of the early support is evaluated from the forcecharacteristics of shot concrete and anchor. The calculation result of a diversiontunnel in Jin ping Hydropower Station shows that this method of "Weak point strongsupport" and "differences support" is a effective way to maintain the security andstability of the deep surrounding rock. It means that this support method isreasonable.