Study On Vertical Bearing Characteristics Of I-Shaped Concrete Core Composite Cement-Soil Pile

Concrete core composite cement soil pile is composed of precast concrete core pile and cement soil pile.Due to the existence of concrete core pile has changed the cement soil pile bearing capacity is low,settlement is large shortcomings,give full play to the advantages of the two kinds of materials,in recent years has been widely concerned by the engineering community.Based on the concrete core soil-cement pile,changing the section shape of the core pile and taking I-shaped precast concrete pile as the core pile,this paper proposes a new type of pile-I-shaped concrete core composite soil-cement pile,so as to increase the bending rigidity of the pile.For the further study of I-section composite concrete core cement-soil pile vertical bearing features,design different I-section core pile section size and length of I-section composite concrete core indoor model test of cement-soil pile and combined with numerical simulation analysis,discusses the different influence factors of the vertical bearing capacity of pile type features,through the research of this paper has made the results of the following several aspects:1)soil-cement performance: with different water cement ratio and different ages,different cement mixing ratio to compressive strength without side limit of soil water,research analysis of the cement mixing ratio of water and soil unconfined compressive strength and elastic modulus,the relationship between unconfined compressive strength of cement-treated soil and cement mixing ratio of approximate a single exponential function relation,elastic modulus of cement-treated soil and cement mixing ratio of approximate linear function relation.2)vertical bearing characteristics of I-shaped concrete core composite cement-soil pile: the vertical bearing capacity of I-shaped concrete core composite cement-soil pile,the axial force of I-shaped concrete core pile and cement-soil pile and the variation rule of lateral resistance of pile are studied and analyzed through the design of model piles with different core length ratio and core content.The results show that the vertical ultimate bearing capacity of I-shaped concrete core composite soil-cement pile is 2~2.5 times higher than that of soil-cement pile.With the increase of core length ratio and core content,the vertical ultimate bearing capacity of I-shaped concrete core composite soil-cement pile increases.Due to the existence of core pile,the axial force of composite pile is abrupt at the interface at the bottom of core pile,and the lateral resistance of pile increases first and then decreases in the composite section,and then increases suddenly at the interface between composite section and non-composite section.3)the numerical analysis model of pile and soil is established,and the "coupling" constraint is set at the pile head to ensure that the I-shaped concrete core pile and soil-cement pile share the load.The test results are basically consistent with the numerical simulation,which verifies the rationality of the selection of relevant parameters.4)the influence of different core length ratio,core content,soil-cement elastic modulus and other parameters on the vertical bearing characteristics of I-shaped concrete core composite soil-cement pile is analyzed.The results show that the load ratio of I-shaped concrete core pile to soil-cement pile is related to the ratio of core length and ratio of core.The coefficients ?1,?2,which are related to core length ratio n and core content m,are introduced to improve the calculation method of load ratio of I-shaped concrete core pile ?1.When the soil-cement elastic modulus increases by a certain value,the settlement of pile tip tends to be gentle.5)the vertical bearing characteristics of square pile and circular pile with the same cross section area of i-shaped core pile are compared and analyzed.The results show that under the same load,when the I-shaped shaped pile is the core pile,the pile top settlement is the minimum,and the I-shaped concrete core composite soil-cement pile has certain bearing advantages.6)on the basis of the existing calculation method of bearing capacity of concrete core composite cement-soil pile,the relevant parameters are modified,and the calculation method of bearing capacity of single pile of I-shaped composite cement-soil pile is proposed,so as to guide the engineering practice.