Study On Load-bearing Deformation Characteristics Of Composite Foundation With Bamboo-reinforced Grid-sleeve Stone Column

The bearing capacity of crushed stone piles is highly correlated with the strength of the soil around the pile.When a crushed stone pile composite foundation is used to treat weak soil,the pile body is prone to bulge and deformation due to insufficient lateral restraint force under vertical load,leading to the failure of the composite foundation damage and thus endangering the safety of the superstructure.For this reason,scholars have proposed to set reinforcing materials on the outside of the crushed stone pile to provide additional lateral restraint and limit its bulging deformation,which can significantly improve the pile stiffness and foundation bearing capacity on the basis of retaining the pile friction characteristics and accelerating the soil drainage consolidation.However,traditional reinforcing materials are mainly geosynthetics,which are made of polymer,and the cost is high and the production process will cause some pollution to the environment.In order to respond to the national "double carbon" development strategy and promote the development of the construction industry in the direction of low carbon and sustainability,it is of great theoretical and environmental significance to seek new reinforcing materials with lower cost and green environmental protection.In this paper,we propose to use natural bamboo reinforcement materials to replace traditional geosynthetic materials in the field of soft ground reinforcement,and focus on the load-bearing and deformation characteristics of composite foundations with bamboo reinforcement grid sleeve and reinforced gravel pile through indoor model tests and theoretical calculations,as follows:Firstly,based on the introduction of the distribution law of bamboo and its structure,the tensile properties of bamboo reinforcement are verified to meet the requirements of the code for reinforcing materials of gravel piles when combined with indoor mechanical performance tests,and then the influence of different factors on the tensile properties of bamboo reinforcement is discussed and its applicability to the field of soft foundation treatment is analyzed.Secondly,through the indoor model test,the bamboo reinforced grating sleeve reinforced gravel pile composite foundation is studied in four aspects: load-settlement change law,pile-soil stress distribution law,pile stress transfer law and pile damage mode,and compared with unreinforced and geogrid sleeve reinforced gravel pile,and then explored the feasibility of bamboo reinforced grating in improving the bearing capacity of gravel pile and reducing the settlement of composite foundation.The feasibility of bamboo reinforced grids in improving the bearing capacity of gravel piles and reducing the settlement of composite foundations was investigated.On this basis,the effects of the length(full-length and half-length)and foundation type(single pile and group pile)on the test are further investigated to obtain the optimum reinforcement length of the bamboo reinforcement grids and the reinforcement effect of different foundation types on the rubble piles.Thirdly,from the bearing mechanism and damage mode of the composite foundation of bamboo reinforced lattice sleeve reinforced gravel pile,the calculation method of its monopile ultimate bearing capacity is discussed,and combined with the calculation method of the ultimate bearing capacity of the composite foundation and the test results of this paper,the calculated values of the ultimate bearing capacity of the composite foundation of unreinforced gravel pile,bamboo reinforced lattice sleeve full-length and half-length reinforced gravel pile are checked to verify the reasonableness of the obtained calculation method.Finally,citing an engineering example,using the single pile ultimate bearing capacity calculation method proposed in the previous paper,comparing the changes of the ultimate bearing capacity of gravel pile before and after reinforcement,further studying the influence law of tensile strength,reinforcement length and pile diameter of bamboo reinforcement grids on the ultimate bearing capacity of pile body.