| With the all-round promotion of high-quality development,China’s demand for transportation is increasing,and the requirements are getting higher,and the problem of reconstruction and expansion of existing roads has become a hot topic of research.Mountain roads are constrained by the geographical environment,often need to be widened by the side of the mountain,which may form an extremely high cut slope of hundreds of meters,and its instability and damage will cause great disasters.Based on the highway project of Shuicheng,this thesis actively carries out the stability research of the excavation process of extremely high cut slope through theoretical calculation and numerical simulation,which provides a certain reference basis for the construction of highway engineering in mountainous areas,and the main research contents and conclusions are as follows:By means of theoretical analysis and numerical simulation,this thesis systematically analyzes the ultimate design height of subgrade between piers of undercrossing highway and the mechanical response results of soil pier structure of undercrossing subgrade affected by different factors.The main study contents and conclusions of this thesis are as follows:(1)During the in-situ excavation of extremely high slope cutting,the slope safety factor first increases and then decreases,among which the slope top inclination angle determines the increase of the slope safety factor,and the larger the slope top inclination,the smaller the increase of the slope safety factor.This shows that if the overall stability of the original cut slope is good before excavation,it is only necessary to consider the influence of the gradual increase of the new cut slope on the overall stability of the rock mass.(2)The change law of the decrease of the safety factor of the new cut slope can be divided into the height control area,the controllable area and the easy control area,and the safety factor decreases linearly with the increase of height after the slope height reaches the easy control area.When the height of the slope remains unchanged,the safety factor decreases linearly with the increase of slope inclination,and the reduction amplitude increases from the height strict control area to the easy control area,and there is no change after the easy control area.(3)The local stability depends on whether the yield plastic zone is penetrated or void,and the degree of failure depends on the load on the penetration surface.Specifically,the original plastic zone of soil and soft loose rock slope can be ignored,while the residual new slope surface of the original plastic zone of hard rock and complex rock slope causes spalling or collapse and the remaining excavated part penetrates at both ends to lead to landslide.(4)The medicine package in the excavation hole of the conventional step should be detonated from top to bottom,and the optimal differential time is moderate;The explosion between the holes should be detonated from left to right,the optimal differential time is large,and the complete explosion time of a single burst hole should be taken.Working conditions with strict requirements for crushed flying stones can be activated at the same time between the burst holes.(5)The pre-reinforcement of the original cut slope should adopt the basic idea of "first use,then treatment";The permanent reinforcement of new cut slopes should be considered comprehensively from the aspects of overall stability and partial stability.The trend of reducing the safety factor of graded support and unsupported slope is basically the same,and the controllable area index can be used to calculate conservatively when unsupported.(6)Drawing on the VCR blasting method of mining engineering,the rock mass with plastic penetration in the excavation can be blasted,and the original plastic zone is used to detonate from bottom to top with large crushing area and small slope displacement.Both safety and blasting are superior to conventional methods. |
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