| Jurassic weak and hard interbedded strata in Three Gorges Reservoir area has unique geological structure and lithology characters,is the key area of prevention of landslide in the Three Gorges Reservoir area.The conventional stabilizing pile design calculation for landslide treatment always consider the bedrock are homogeneous rock,ignoring the impact of geological structure and lithology characters on deformation of stabilizing pile.On the basis of field investigation,previous research and developed pile–landslide physical model device,the paper detailed studies the influence of orthogonal joints linear density on strength degradation degree of the weak and hard interbedded strata and embedded mechanism of stabilizing pile by the method of indoor model test and numerical simulation experiments.The strength degradation of weak and hard interbedded strata with developed various linear density orthogonal joint is studied,and the correction coefficient of the embedded depth of the stabilizing pile is proposed under various line density orthogonal joint.The main results are as follows:(1)Choosing the Guizhou town Zigui County in southwest Jurassic strata as study area,a field investigation is carry out in this area to acknowledge development features of Jurassic strata.To investigate orthogonal joints development features in weak and hard interbedded strata,the measurement rock structural surface distribution characteristics is conducted including structural plane dip angle,dip direction,trace length,endpoint type,gap width,filling type and so on.The indoor rock mechanics test is carried out to obtain the physical and mechanical parameters of typical rock in Jurassic.By using the indoor rock ultrasonic test,the influence of orthogonal joints linear density on physical and mechanical parameters of rock is studied.The results show that the orthogonal joints seriously decrease the strength of rock mass.This strength degradation degree is obviously at the first orthogonal joints generate and gradually become weak with the increase of orthogonal joints linear density.(2)On the basis of the field investigation,indoor test and developed pile–landslide physical model device,the paper studies the influence of upper hard and lower weak bedrock developed with various orthogonal joints linear density on embedded mechanism of stabilizing pile by the method of simple variable method.Through the analysis of the collection and comparison of pile strain data,the results show that the different orthogonal joint linear density has a greater difference on the deformation of stabilizing pile.The strength of rock mass directly decreases with the content of bedrock orthogonal joints.As the increase of bedrock orthogonal joints linear density,the bedrock is divided into a series of block and it is harder for the part of the stabilizing pile below the slip surface to receive resistance from the bedrock.Under this case,the overall of stabilizing pile is more obvious,it is not conducive to the stability of landslide.(3)In order to verify the accuracy of physical model experiment,the paper carried out three groups of same condition 3DEC numerical simulation test by enlarging physical model size at the principle of similarity.The pile bending moment and displacement of stabilizing pile at the same position is collected for comparison analysis.The comparison results show that the deformation characteristics of the landslide and stabilizing pile in numerical test has consistent with physical model test.To study the influence of 2D orthogonal joints linear density on embedded mechanism of pile,many cases of numerical simulations is conducted.The results show the displacement at pile head is gradient growth with increase of joints linear density along pile width.(4)Taking the Majiagou landslide as geological model and combining field GPS displacement monitoring results,three-dimensional discrete element numerical model is established to study the deformation and moment of a stabilizing pile embedded in bedrock developed with orthogonal joints by using the method of parameters reversal.The relationship between various orthogonal joints linear density and minimum embedded depth of stabilizing pile under the principle of certain deformation is discussed in detail.The modification coefficient of minimum embedded depth of stabilizing pile under various orthogonal joints linear density is proposed by using orthogonal test.The results show that the relationship between the minimum embedded depth of stabilizing pile and orthogonal joint linear density is exponential function;when the line density is too large,the embedded depth of stabilizing pile is not the main factor affecting the deformation of stabilizing pile,i.e.,the influence degree of embedded depth on pile deformation has a limit state. |
