Study On Mechanical Influene Factors Of Double-row Stabilizing Piles

The occurrence of large landslides that threaten the life and poverty of people are becoming more and more frequent as the economic development and climate changing. As a result, the double-row stabilizing piles which can provide larger sliding resistance are widely used in the landslide-control projects. However the study of mechanism of double-row stabilizing pile is in appears of the application of the double-row stabilizing pile, many application cases of double-row stabilizing piles are based on the design experience of single-row stabilizing piles. In this thesis, based on the data of Hongyan landslide project and utilizing the theoretical and numerical methods, a theoretical model in which the "shadow effect" is considered is established. Influences of different scenarios of embedded length of the double-row stabilizing piles on the internal force, the deflection, the sliding resistance and the soil pressure around the piles are studied. Constructional time delay is also introduced in computational model of double-row stabilizing piles. A theoretical method used to predict crack initiation in stabilizing piles is established based on the head displacement data of stabilizing piles. Application of vertical pre-stressing force in the stabilizing piles is systematically studied and validated. The main research contents are:(1). Combined with elastic foundation beam theory, a computational model of double-row stabilizing pile is established by assuming that the displacement of sliding mass is uniformly distributed with depth. In the model, a concept of soil displacement ratio, which is defined as the soil displacement ratio around the rear stabilizing pile to the front stabilizing pile, is introduced. The computational process of the theoretical model is realized by MATLAB. Feasibility of the model is validated by comparing the results between the model and FLAC3D model.(2). Influences of different scenarios of embedded length on the deflection, internal force, sliding resistance and soil pressure are studied using three-dimensional numerical method.(3). Based on the elastic foundation beam theory, a computational model in which the constructional time delay is considered is established. Influences of constructional time delay on the internal force and deflection of double-row stabilizing piles are discussed based on the data of Hongyan landslide project.(4). Based on concrete theory and head displacement of stabilizing piles, a theoretical method used to predict crack initiation in stabilizing is established. The time and position of crack initiation can be determined by this method. The method is validated by data of Hongyan landslide.(5). Based on the researches on vertical pre-stressing force done by the former researchers, specific applied process of pre-stressing force according to head displacement of stabilizing piles is proposed, during which dynamic control of crack can be realized. The feasibility of vertical pre-stress force applied in practical engineering is verified.Some innovative conclusions are drawn through above mentioned researches:(1).The "shadow effect" can be properly considered in the computational method based on displacement of sliding mass. Analytical solution of the method based on the displacement of sliding mass is more convenient to be obtained than that of the method based on soil pressure.(2). Embedded length obviously affects the deflection, internal force, sliding resistance and soil pressure around the stabilizing piles. This kind of influence is dependent on the magnitude of the boundary displacement applied on sliding mass.(3). Construction time delay obviously affects the deflection and internal force of the double-row stabilizing piles, especially for the rear stabilizing pile which is installed earlier. The constructional time delay is optimized based on the principle that the maximum tensile stress in the front and rear stabilizing piles are approximate to each other and the sum of maximum bending moments are the smallest. (4). The time and position of the crack initiation of the stabilizing piles in Honayan landslide are determined by the crack discriminant proposed in this thesis. The results are validated by the stress data of the reinforcement bar, and the feasibility and accuracy are also verified at the same time.(5). Dynamic control of cracks can be realized by applying pre-stressing force according to the head displacement of stabilizing pile.