Study On Tunnel Model Test And Support Structure Optimization Of Carbonaceous Phyllite

In the construction of mountain tunnels in the western Sichuan region of China,soft rock tunnels with typical phyllite rock tunnels are often encountered.Due to the influence of historical earthquakes in western Sichuan,especially under the influence of the Wenchuan earthquake,there are generally hidden damages in the interior of the rock mass.The rock rock integrity is further reduced and the water permeability is further enhanced.During the tunnel excavation process,The soft rock mass generally shows obvious characteristics of broken and loose,making the construction of these soft rock tunnels more difficult and frequent construction problems.At present,one of the main contradictions encountered in the above-mentioned soft rock tunnels is that the design Parameters of the support structure corresponding to the classification criteria of the existing road tunnel surrounding rock are difficult to effectively control the deformation of the surrounding rock during actual construction,and the large deformation of the soft rock tunnel is Local landslides and other issues not only seriously affect the construction progress and construction safety,but also increase the investment in construction.Therefore,in-depth study of the physico-mechanical properties of tunnel soft rock and the characteristics and laws of surrounding rock deformation in construction are the basis for obtaining large-scale deformation control technology of surrounding rocks.Based on this,the optimization of support structure is studied,which is a soft rock tunnel.Support structure optimization provides theoretical basis.Based on the engineering background of the Mima Highway No.3 tunnel in Mia Luo,the field investigation,monitoring and measurement,theoretical analysis,indoor physical and mechanical tests,numerical simulation and similar model tests were applied to the study of carbonaceous phylloid rock masses.The traits,characteristics of tunnel deformation and the mechanism of large deformation of tunnels were thoroughly analyzed,,and optimize the construction support system for soft rock tunnels.The following main results were obtained:First,on the basis of a thorough investigation of the geological conditions of the Miyaluo 3 tunnel project,the existing support Parameters and deformation monitoring data of the surrounding rock of the carbonaceous phyllite section are used to analyze the deformation characteristics and supporting deformation characteristics of the surrounding rock of the phyllite section.The basic physical and mechanical Parameters and mechanical properties of phyllite derived from indoor physical and mechanical tests.According to the genesis mechanism,the large deformation of the surrounding rock is divided into three types: lithologic control type,rock structure control type,and structural fracture zone control type.The main influencing factors of deformation of carbonaceous phyllite surrounding rocks are obtained:: 1.Carbonaceous phyllite rock lithology soft,and it is significantly softened with water;2.Groundwater development in the local tunnel section of the tunnel;3.The structural plane of the tunnel is relatively developed;4.Affected by the Miyaluo fault,the surrounding rock mass is broken;5.Failure to strengthen support measures in a timely manner;6.Excavation face deformation blasting more frequent.Secondly,after the study of the carbonaceous phyllolitic lithology and the influencing factors of large deformation,the preliminary support structure optimization plan and ideas were developed using finite difference software,and the calculation model was established based on the geological conditions of the actual tunnel size.The effect of strengthening the Parameters of the main supporting structure of the tunnel on the control of deformation.The results show that the optimization of anchor bolts has less effect on the control of deformation,and the optimization of the initial thickness,steel arch sPacing,and the thickness of the second liner is more important.The optimization of the support structure in the physical simulation test is mainly aimed at the latter three.Finally,according to the similarity principle,the model materials such as surrounding rock,steel arch,shotcrete,and secondary lining were selected through experiments,and the model test chamber and measurement system were independently designed to carry out the optimization design of the tunnel support.The results show that the thickness of shotcrete is increased from 24 cm to 30 cm,and the distance between steel arches decreases from 80 to 64 cm.This can better enhance the stability of the surrounding rock.The thickness of the second liner increases from 48 cm to 64 cm and can better withstand the continuation of the later period of the surrounding rock.Deformation,with sufficient safety reserves also has good economics and feasibility.The optimized supporting measures can make the supporting structure have a good ability to control the deformation of the surrounding rock,and it can make the supporting structure moderate in force,which is a more reasonable solution.