Study On Construction Technology For Highway Tunnel With Swelling Mudstone

Liangjiashan Tunnel mainly crossing swelling mudstone is the controlling engineering ofTianshui Transit Line of Lianhuo Highway. The in-situ cast two-pass lining had been adoptedas the tunnel structure, but during the construction of this lining, large deformation ofsecondary lining and even the collapse of tunnel have occurred due to thegroundwater-induced expansive effect of mudstone. Hence, closely combined with theconstruction practice in swelling mudstone of Liangjiashan Tunnel, this research will studythe engineering geological properties and grading of swelling mudstone and proposecorresponding calculating parameters. Then by comparison the results from in-situ monitoringand numerical simulations, the construction technology more suitable to the geologicalcharacteristics of this project will be developed and suggested.The following researches were conducted with the backing of the swelling mudstonetunnel of Tianshui Transit Line of Lianhuo Highway:(1) The geochemistrical and mineral constituents of mudstone were obtained through thelaboratory tests where all the samples were taken from the typical sections in tunnel duringconstruction. The microstructure of mudstone was studied by using image processingsoftware. Referred to the empirical method and theoretical calculation of similar stratum bothhome and overseas, the calculating physical and mechanical parameters for the mudstone inLiangjiashan Tunnel were determined.(2) The physical, water-related and mechanical properties of mudstone in LiangjiashanTunnel were gained through laboratory tests. The swelling mechanism of swellinggeomaterials and the existing assessing methods of swelling rocks were comprehensivelyanalyzed. Then a new method was put forward that can quantitatively assess and grade theswelling rocks. The swelling of mudstone in Liangjiashan Tunnel was graded by using thisnew method and the tested data of the mudstone from Liangjiashan Tunnel.(3) The deformation and stress characteristics of swelling surrounding rock, primarysupport, secondary lining and steel arch centering were obtained through in-situ monitoring inLiangjiashan Tunnel. The monitoring data were processed through the theoretical analysis inorder to verify the reasonableness of the data. The results from both in-situ monitoring andtheoretical analysis indicated that the tunnel structure produced by using the constructionmethod of NATM （New Austria Tunnelling Method）was stable.(4) The numerical simulations were conducted by using the code of MIDAS/GTS wherethe input calculating physical and mechanical parameters were determined from tested data.The swelling effect of mudstone was considered by shear dilation angle. The comparativestudies with and without consideration of shear dilation angle presented the stress variationsof tunnel constructed by NATM. (5) By using the numerical simulations, the stress and deformation characteristics ofsurrounding rock and tunnel structure constructed with the method of both two-pass liningand composite support were compared. It was concluded that the more suitable supportstructure for Liangjiashan Tunnel with mudstone should be composite support, which not onlycan meet the requirements of the deformation of surrounding rock and stress in supportstructures, but also have an advantage in degree of construction difficulty, safety andeconomy.In all, this thesis chose the actual engineering as study objective, suggested the relatedtechnical measures through the comprehensive study on engineering geological properties ofswelling mudstone and with the combination of in-situ monitoring and numerical simulations.The results have been applied to the engineering practice and yielded good economic benefitsand social benefits, which not only can enrich the research contents of engineering geologicalproperty of mudstone, but also can provid the valuable consultation for similar engneering.