Research On Creep Large Deformation Instability Mechanism And Control Technology Of Deep Roadway

Affected by mining environments with three“high”and one“disturbance”,the deep roadways can easily present large deformation and extreme rheological behaviors and are seriously damaged from the supporting structure.So they can not be easily controlled with conventional support methods,such as anchor net spray,the bolt-grouting and anchor net spray plus U-section steels.Therefore,a set of practical and new supporting theory and system need to be put forward for providing important technology support in deep roadway surrounding rock control.Based on the creep large deformation problem on the haulage-dip of Quandian coal mine,failure mechanism of deep roadway and control technology of surrounding rock were studied generally in this dissertation.And by using the field measurement,theoretical analysis,numerical simulation,laboratory tests and industrial tests,a supporting theory of multistage anchoring-bearing stratum was proposed.Then combined with idea of yieldable support and full-face enclosed support,a new coupling yieldable support system of“strong-weak-strong”was established,and the tunnel support parameters and support form were optimized.At last,the final application effects could be confirmed by applying the supporting theory to industrial tests.The results and conclusions in this dissertation were as follows:?1?Based on the aging fracture characteristics of the belt down,the basic mechanics and creep test of sandy mudstone under different confining pressure were carried out and the new one dimensional model of nonlinear viscoelastoplastic creep mechanics was also established which can effectively reflect the creep three stages of sandy mudstone.Then,based on the tensor theory,the three-dimensional expansion form of the nonlinear creep model was derived and the Creep parameters were fitted by nonlinear least square method to verify the accuracy of the model.The creep fracture morphology of specimens under different confining pressures were obtained by SEM scanning and the macroscopic and microscopic creep fracture mechanisms of the sandy mudstone were also revealed.?2?The finite difference method was used to realize the FLAC^3D secondary development of this creep model and the accuracy of simulation results is verified.Based on the"constraint-convergence"method,the creep instability progressive failure process of the belt downhill under different stress release coefficients was researched by numerical simulation and the creep instability mechanism was also summarized.The stress dispersion mechanical model of surrounding rock strengthened by full-length anchoring prestressed bolt is established,and the expression of axial compressive stress of surrounding rock along its bolt body is obtained.The influence of bolt pretension,length and pallet size effect on the stress distribution is analyzed,which provides an important theoretical basis for the support theory.?3?The concept of“multistage anchoring-bearing stratum”was firstly presented and its construction principle,structural feature and key technology were also introduced.The coupling mechanical model of the fully anchored bolt-surrounding rock considering the effect of support density was established and the stress,displacement and plastic zone radius of surrounding rock were deduced.Then,the influence of the bolt low-spacing on the mechanical response of surrounding rock were also analyzed.Meanwhile,the FLAC^3D software was used to study the expansion mechanism of compressive stress zone?maximum principal stress?of surrounding rock under different supporting parameters and forms,and the reasonable suggested values for supporting parameters of the anchor bearing layer were given.?4?Combined with the engineering practice,the new“strong-weak-strong”supporting system was proposed with the theory of“multistage anchoring-bearing stratum”and the relationship between the two methods was also described as well as the supporting form and parameters on the haulage-dip were optimized.The effects of yieldable space and the cross-section of enclosed U-steels on the deformation of surrounding rock were analyzed by FLAC^3D,and the optimal yieldable thickNess and the type of U-steels were determined.Based on the secondary development result of the nonliner viscous-elastic-plastic creep constitutive model in FLAC^3D,the stress and deformation evolution laws of surrounding rock with the excavation time were discussed for verifing the reliability of the support scheme.?5?Applying the research results on the haulage-dip of Quandian coal mine,and the integrated dynamic monitoring on the deformation,fracture range of surrounding rock and axial stress of bolt and U-steels were carried out by using the methods of geological radar,cross stitch and nondestructive testing.The monitoring result show that the“strong-weak-strong”supporting system with“multistage anchoring-bearing stratum”at the core could manage large creep deformation problem of soft rock roadway under deep and high stress and extreme rheological behaviors.There are 154 pictures,28 tables and 190 references in this dissertation.