Areas Of Weakly Expanding Rocks (Soils) With Interlayer Structures Subgrade Expansion Deformation Study

Aiming at the quantitative prediction and evaluation of the expansion deformation of the subgrade in the weakly expanding rock(soil)area with interlayer structural characteristics of high-speed railways,two typical remodeling weakly expanded soils and two typical remodelings were studied through indoor dry and wet cycle experiments The expansion deformation law of weakly expanding rock under the dual action of dry and wet cycle and with(without)load was studied through indoor interlayer structure experiment,and the expansion deformation law of weakly expanded rocks with different structural patterns under(without)load was studied,and a model of weakly expanded soil subgrade of interlayer structure was established to study the production of different structures The length of the subgrade when the expansion deformation trend of the weak expansion soil subgrade of the interlayer structure tends to be stable.The results show that:(1)under the action of dry and wet cycle,the sandstone only shows shrinkage deformation,and the trend is the same,that is,after a short and rapid contraction deformation occurs with the water absorption of the sample,its shrinkage deformation slows down and finally reaches a stable state;the mudstone is expanding under no load and low load(less than 22.69 k Pa)and shrinks under high load(greater than 22.69 k Pa);the silty clay is under no load and low load(less than 22.69 k Pa).It is intumetic at 25 k Pa and shrinks at high load(greater than 25 k Pa),while red clay is expansive and high at no load and low load(less than 41.5 k Pa).It is also shrinkage in the loaded(greater than 41.5 k Pa)state.(2)Under the same conditions as the thickness ratio of the sandstone layer and the weakly expanding mudstone layer,the weak expansion rock with the characteristics of the interlayer structure has the largest expansion deformation in the flat layer production structure,and the vertical layer is the smallest in the oblique layer.(3)When the thickness ratio of the sandstone layer to the weakly expanding mudstone layer is greater than 2:1 when the thickness ratio of the sandstone layer to the weakly expanding mudstone layer is greatly reduced when there is no load,the shrinkage deformation of the weak expansion rock with the interlayer structural characteristics is greatly reduced;when the overlying load exceeds the expansion force of the weakly expanding rock with the interlayer structural characteristics,the shrinkage deformation occurs when the weak expansion rock with the interlayer structural characteristics absorbs water,and the greater the thickness ratio between the sandstone layer and the weakly expanding mudstone layer,the smaller the shrinkage deformation.(4)The expansion deformation of the weak expansion soil subgrade of the flat layer interlayer structure is central arched;the expansion deformation of the weak expansion soil subgrade of the oblique interlayer structure is gradually decreased along the direction of the oblique layer;the expansion deformation of the weak expansion soil subgrade of the oblique interlayer structure is jagged(5)When the length of the weak expansive soil subgrade of the flat interbedded structure with the layer thickness ratio of 1:1 reaches more than 70 m,the expansion deformation trend remains stable;When the length of weak expansive soil subgrade of flat layer interbedded structure with layer thickness ratio of 2:1 and layer thickness ratio of 3:1reaches more than 50 m,the expansion deformation trend remains stable.