Research On Characteristics Of Deformation And Surrounding Rock Pressure In Loess Highway Tunnel Based On Centrifugal Model Test

With the key point of research on deformation rule of loess highway tunnel, and bymeans of indoor model test and theoretical analysis, this text deeply analyses the deformationrule of the surface and stratum below caused by the loess tunnel construction, and finds outthe three main factors which influence the deformation characteristics of the loess highwaytunnel and gives susceptibility, and analyses and revises the applicability of peck formula,which is mainly used in tunnel sedimentation trough predicting, on loess highway tunnel, andputs forward a new load calculation formula for surrounding rock design of the loess highwaytunnel. Main research results are as follows:(1) When choosing0.5D of double-hole spacing, it is easy to form stress anddeformation strong influence area between holes, and it is necessary to reinforce the middlesoil; when choosing D spacing, the steady wide-base bearing soil column can form betweenholes; when choosing1.5D spacing, the maximum of each stratum sedimentation trough istransfers to above the vault from the midcourt line of two holes, and sedimentation value ofabove the vault of the anterior hole are greater than the subsequent hole; when choosing2D,two holes excavation has little influence on middle soil column, and stratum sedimentationcurve can be seen as the composition of two single-hole excavation. For closely spacingloess highway tunnel, the reasonable spacing between two holes can be D; for separatedtunnel, the spacing of tunnel two holes can be at least greater than2D.(2) The stratum subsidence and deformation caused by tunnel excavation is a complexprocess, the loess tunnel which the burial depth exceeds certain depth would appear bearingvault. With the increase of double-hole spacing, the distance between the stratum which themaximum value of each working condition sedimentation appears and vault top increases,appearing16-20m stratum separately; it shows that the soil differential settlement formsbearing vault, and its height increases with the increase of double-hole’s spacing.(3) According to the stratum sedimentation trough curve, find the point of inflection andfit the limit of the sliding wedge after the tunnel excavation, by analysis and research, itconfirms that the included angle between the fracture plane caused after the excavation of thismodel test tunnel and the horizontal plane is70°~74°. According to Mair equation K valuecalculation form, a simple method to evaluate the vertical displacement of certain depthstratum below the surface because of the loess tunnel excavation, this method can predict theloess tunnel surface and below the soil settlement. (4) Based on soil mechanics equilibrium condition, a calculation method of shallowburied loess tunnel surrounding rock pressure is deduced. Comparing the results from severaltheory of computation with the field measured value, the result by using the calculationmethod proposed in this text is close to actual measured value, which can provide referencefor the surrounding rock pressure calculation of similar project.