| China's pearl river delta region has a large number of soft soil layers,most of which are silt or silty soil with a depth of 20-60 meters,with multiple layers and uneven thickness,various types and complex causes.Due to the developed economy and active market in these soft soil areas,a large number of infrastructure projects are under construction to meet the demand.The characteristics of soft soil,such as high water content,large pore ratio and high compressibility,result in low carrying capacity,poor engineering properties and long consolidation time,which are not conducive to the development of engineering projects.In view of some engineering problems existing in deep soft soil foundation under existing buildings,such as too large settlement and insufficient bearing capacity,the treatment method of strengthe ning deep silt foundation should be put forward according to local conditions.Core pile is composed of core pile with high strength and cement-soil pile body.The increase of lateral friction resistance and end friction resistance of composite pile is realized by the large area on the side and bottom of cement-soil pile bo dy,and the pile core with high strength can make up for the lack of strength of cement pile body.It is characterized by low cost,little pollution,no soil squeezing effect,little influence on existing buildings and underground pipelines,flexible and convenient construction of machinery and tools.In this paper,based on an energy chemical industry plant rock fill deep soft soil foundation reinforcement project,based on the deep soft soil under existing buildings rockfill subgrade settlement is too large disasters cause the upper structure of the structure of the problem,this paper adopts theoretical analysis,numerical simulation,the static load test and field monitoring means of the combination of high pressure jet grouting under the vertical load micro steel tube pile foundation of plain concrete pile bearing characteristics and deformation mechanism were studied.The main research contents are as follows:(1)Under the vertical load,the site static load test was carried out for the micro-pipe-filled concrete piles with different core insert depths.The distribution rules of load-settlement and lateral friction of pile under vertical load are studied.The results show that it is necessary to select the proper depth of steel tube insertion when the bearing capacity is satisfied.(2)Finite element analysis software Midas is adopted to carry out simulation calculation and analysis of micro-concrete filled steel tube piles with high-pressure rotary jet grouting(different insertion depths of steel tubes,thickness of rotary jet grouting piles and elastic modulus of rotary jet grouting piles),so as to determine that choosing a reasonable insertion depth under the premise of meeting the bearing capacity is conducive to saving economic benefits;The change of elastic modulus has little effect on the settlement of pile tip.The diameter of the rotary jet pile should be 400 mm.The comparison and analysis of the numerical simulation and the measured results verify the scientific rationality of the finite element numerical simulation,reveal the load transfer mechanism of the core inserted composite pile,and determine its failure mode under the action of load.(3)By changing the insertion depth of core-inserted composite piles,the influence of various parameters on the vertical bearing characteristics of core-inserted composite piles is studied;Based on the research results of the new composite pile,the formula for calculating its compressive bearing capacity is proposed.(4)Establish the finite element model of composite pile reinforcement in the area where the pipe gallery is located,calculate and analyze the overall settlement and deformation law of the foundation after reinforcement,obtain the simplified calculation formula of settlement and deformation,and conduct preliminary post-construction settlement prediction analysis based on this. |
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