Laboratory Model Test Of RHS Pile On Inclined Bedrock Under Horizontal Vibration Load

With the continuous development and innovation of industry and science and technology,geotechnical engineering construction projects are gradually increasing,and pile foundation is more and more widely used.Many projects need to choose sites with poor engineering geological conditions.For example,some LNG storage station construction projects have to be selected on the site with large undulating surface of bedrock.Under such engineering geological conditions,unequal length rock socketed pile group foundation needs to be designed and applied.The pile end of the foundation pile needs to pass through the overburden and be embedded into the bedrock.The pile length in the pile group is short and relatively constrained by the bedrock,and the stress concentration is easy to occur at the rock socketed end of the foundation pile.In the case of earthquake,the horizontal deformation capacity of short pile is weaker than that of long pile,which will lead to the disharmony of the overall horizontal deformation of pile group under seismic load and the early failure of short pile.In this case,there is an existing design to reduce the horizontal constraint of bedrock,which is called RHS(reducing horizontal stiffness)pile for short.In this paper,the indoor model of unequal length rock socketed pile group is established according to the similarity theory.By designing different comparative test schemes,the horizontal deformation and bearing characteristics of ordinary rock socketed pile group with different bedrock inclination angle and the short pile of rock socketed pile group with a certain reduced restraint section under the action of horizontal dynamic load are studied,and for RHS piles with a certain inclination angle of bedrock,different lengths of restrained sections are designed.The main contents of this paper are as follows:The first part summarizes the current research status of rock socketed pile,indoor model test of pile foundation and pile foundation under load at home and abroad from the aspects of model test and theoretical research,collects and arranges relevant data,and summarizes the relevant research contents of this paper.The second part calculates the geometric similarity ratio of relevant components of the model test according to the relevant theorems of the similarity theory,and selects the relevant test materials in the test model according to the selection principle of similar materials in the model test.The relevant bearing capacity of single pile in the model test is simply estimated,and the appropriate loading system is established.The bedrock embedded section and unequal length model pile group foundation in the model test are designed according to the design idea and construction process of reduced restraint RHS pile in the actual project.In the third part,according to the research content,three groups of comparative model test schemes under horizontal dynamic load are designed,and the test data and results are studied and analyzed.The first group of model tests show that different bedrock inclination angles have different effects on the horizontal deformation and bearing characteristics of rock socketed piles.It is concluded that when the bedrock inclination angle is small,the overall horizontal deformation of rock socketed piles is more coordinated,and the bearing performance of pile foundation is relatively good;The second group of model tests shows that the design of a certain length of restraint reducing section for the rock socketed end of short pile in rock socketed pile groups with different bedrock inclination angles can improve the horizontal deformation capacity of short pile,promote its coordination with the horizontal deformation of long pile,and improve the bearing capacity of pile groups;The third group of model tests shows that the design of different lengths of restraint reducing sections for RHS piles with the same bedrock inclination angle has different effects on the overall horizontal deformation and bearing capacity of pile groups.It is concluded that the design of restraint reducing length of rock socketed section of short piles in rock socketed pile groups must be within a certain reasonable range.The design length of restraint reducing section is too large,resulting in too small restraint of foundation pile,easy sliding of rock socketed end,resulting in too large horizontal deformation of short piles,Cause negative effects.