Study On Grouting Uplifting Law And Control Method Of Surrounding Rock On Urban Shallow Tunnel

In recent years,China's economic construction has developed rapidly and the process of urbanization has entered an accelerated development stage.The rapid increase in population has led to the continuous expansion of cities.At present,space has become one of the important factors constraining urban development.The development of city and scarcity of living space makes the development and utilization of underground space become an inevitable trend.The construction of underground projects will inevitably affect the existing surface and underground facilities in the city.In particular,the municipal tunnel project has a great influence on the existing facilities in the city due to its long planning line and shallow depth.If it is not properly constructed,it can easily cause adverse consequences such as road collapse and buildings collapse,which will affect the normal operation of the city.The engineering practice shows that improving the stability of the formation through grouting is an important method to reduce the influence of shallow underground engineering construction on the surrounding environment.However,it is difficult to control the construction process of grouting,shallow grouting can easily cause surface bulge,resulting in the ground road operation interruption,building tilt and other adverse consequences.In view of the surface uplift caused by the grouting construction of shallow underground in cities,the influence laws of compaction grouting and fracturing grouting on surface lift were studied respectively through the theoretical derivation,laboratory tests,numerical simulations.And the relationship of ground surface lift displacement between uplift displacement,surface soil properties,grouting depth,and other factors was established.Based on the random medium theory,the theoretical prediction method for surface uplift displacement under grouting action was proposed,and was verified through indoor experiments and actual engineering.The specific research results are as follows:(1)Based on the random medium theory,the ideal spherical compaction grouting uplift model and the horizontal fracturing grouting uplift model were established.Based on the two surface uplift models,the corresponding surface uplift displacement prediction algorithm was proposed and the relationship of surface uplift displacement between the grouting depth,grouting diffusion radius and other factors was quantitatively analyzed.On this basis,based on the principle of linear superposition,the prediction formula for surface uplift displacement under double-hole grouting conditions was deduced.(2)The model test system for grouting uplift mechanism was designed.The grouting uplift test under the conditions of compaction grouting and fracturing grouting was carried out respectively.The law of surface uplift displacement during grouting was systematically studied.And based on the test results,the grouting uplift coefficient y was proposed,and the expression of lift coefficient was deduced.(3)Based on the discrete particle flow method,PFC software was used to simulate the grouting process,and the grouting pressure was applied through the servo mechanism.The comprehensive physics of the injected soil in the grouting process and the surface elevation were studied,and the low of Surface uplift caused by ideal sphere compaction grouting was analyzed.(4)Apply the research results obtained in this paper to the surrounding rock grouting reinforcement project of the Yuhan Road tunnel in Jinan,optimize the parameters such as grouting depth,grouting rate and grouting pressure to ensure the effect of grouting reinforcement.At the same time,an effective control of the surface lift displacement is achieved and the normal passage of the surface road is ensured.