Feasibility Study Of Pipe-jacking In Deep Rock Mass Of Coal Mine

With the development of coal industry,deeper coal mining makes roadway excavation get involved into deep and complex mining environment.Coal mine industrial facility and auxiliary roadway,like high drainage roadway,have to face deep rock stratum.Some scholars summarized the deep mining environment characteristics as high geostress,high geothermal and high karst hydraulic,and traditional excavation methods,like drilling and blasting,is time-consuming,which is unsafe for workers in gaseous and complex coal mine strata conditions.It is necessary to find a miniaturized,mechanized,automated,intelligent and infomatized technique for roadway excavating in deep rock stratum.For this demand,this paper will carry out research in tunnel long-term deformation and pipe jacking correction technique,shown as following:(1)Basing Burgers model,this paper calculates the radial displacement of tunnel edge.According to the result,deformation stages of radial displacement can be divided into instantaneous deformation stage,creep decaying stage and creep stabilization stage.For long-term construction of pipe jacking project and particularity of pipe jacking technique,it can be considered that radial displacement increases continuously in the whole pipe jacking construction period.Basing characteristics of long-term radial displacement of tunnel edge,this paper put forward theory for pipe section lock prevention,and with certain rock parameter,jacking speed and design length,this paper propose suggestion for over excavation selection.This paper also builds numerical model for theory verification.Radial displacement of tunnel edge in deep rock stratum is shown in numerical model and simulated result is similar to the theoretical result,which verifies the credibility of the theory.(2)For long distance pipe jacking project,this paper assumes travel curve shows many "S" type waveforms under repeated correction.With same initial deviation,correction angle and similar initial declination of each waveforms,each waveforms of travel curve can be assumed as same,and mathematical expression for each waveforms can be got.Different shape of travel curve will surely affect pipe jacking resistance,and this paper put forward theory to describe this kind of effect.With this theory,this paper also provides correction factor for resistance calculation in non-linear jacking.Basin the theory,it is also clear that bigger correction angle makes resistance increase,while smaller angle makes deviation maximum of each correction curve bigger,which makes travel curve deviate from design center axis easier.Therefore,it need to choose proper correction angle in actual pipe jacking project.