Study On Deformation Of Collapsed Loess In Metro Construction By Shielding

XiAn metro construction is first metro engineering in collapsed loess in the world, in that there are many questions to be solved such as "many studies,much difficulties, little parameters and no data ",which could be risk resource of metro engineering in crossing under old wall,tower and river directly,so that the "study on deformation of collapsed loess in metro construction by shielding" is put forward here.Firstly,the collapsed loess is studied by information,and put forward the dualistic structure of collapsed loess for shielding in loess.Based it,the law of loess settlement in shielding was found out by analysis of data of shielding settlement by supervision and demonstrated by digitally in theory.After study on deformation of loess by shielding,innovation achievements have been gotten as the following.1.Against metro influence in other cities,there is special properties of metro in Q₃,Q₄,collapsible loess of XiAn city.With change of water content w and saturation degree S_r,there is differences of physical and mechanical properties of Q₃,Q₄ collapsible loess,and therefore the dualistic structure of loess are formed naturally. After analysis of loess,theory of dualistic structure of collapsed loess is gotten.The above block of unsaturated loess in the structure has relationship with water content w and degree of saturation S_r,and the other one,saturated loess under water,does properties of general weak clay with collapsible loess.There is coincidence of deformation in dualistic structure.when one dualistic body is forced,the above block delivers the action to under one,in coincidence the deformation of under block is plastic deformation,making the above settlement in elastic along fissure.2.Settlement when shielding in above block of dualistic structure,the are 5 phrases in settlement under construction,in which the loss of clay by shielding and collapsed loess after jetting are two main factors,loss of body for 15²3 mm,collapsed loess for 9¹5 mm and consolidation for 2⁵ mm.Based deformation from shielding, the improved formula Peck is gotten in,kis synthetic to contain factors,k = 1.30～1.45.3.When shielding under block of dualistic structure,against shielding in above block,the settlement curve is flatter more,there is one factor impacting deformation-loss of clay.Maximum settlement by the loss is 16.88～30.71 mm,and one pressure arch appears in above block,which restrains deformation of under block.4.Stability of clay face and shielding knife face pressure,after analysis of stability of clay face,get the critical pressure of shielding face,which has influences in 10～30% of diameter of face.The shielding is kept on stability by the financial pressure.