Research And Development Of Micro-disturbance And Low-carbon Deep Mixing Technology For Solidifying Soft Soil

The deformation restriction of existing buildings is one of the key factors for the safe construction of deep mixing pile in the densely built area of city.Conventional deep mixing pile only pays attention to the construction efficiency and pile forming quality during foundation treatment,and the soil disturbance around the pile in the construction area near the existing building is less considered.The existing theoretical research on the interaction between deep mixing pile and soil has not caught up with the practice of urban foundation treatment engineering.The force transfer form of deep mixing pile in soil drilling process still needs to be further studied.Solidified materials are still mainly inorganic cementing materials such as traditional cement,which is inconsistent with the current concept of low-carbon development.In this paper,the micro-disturbed deep mixing pile is taken as the main research object,particle flow numerical simulation,engineering case analysis and research and development of high efficiency and low carbon curing materials are taken as the research content to carry out the research and development of micro-disturbed low carbon soft soil deep mixing and curing technology,which has a positive guiding significance for the foundation treatment with deformation control requirements,carbon peak and neutrality targets.(1)Based on the basic principle of particle flow numerical simulation,the basic hypothesis,force-displacement law,motion law and basic contact model of particle flow in PFC3 D particle flow software are analyzed and explained.Because the meso-component composition of the parallel bond model is similar to the basic physical properties of the actual cohesive soil,the envelope of the molar Coulomb strength simulated by parameter calibration is similar to the actual cohesive soil.The parallel bond model,as the basic contact model of particle flow numerical simulation,provides the hypothesis conditions for the research.(2)By combing the construction technology of deep mixing pile,a double-layer soil foundation model of silty clay and silted powdered clay is established by using PFC3 D particle flow software.The simplified models of single-blade stirring drill body,two-blade stirring drill body and micro-disturbed stirring drill body were established,and the disturbance of three kinds of stirring drill bodies on soil around pile was analyzed in the process of soil moving,and the feasibility of micro-disturbed stirring drill body in soil deformation control was verified.It is found that the velocity and free blade of the stirred drilling body are the key factors affecting the soil disturbance around the pile.In the range of 2.5 times the pile diameter from the pile core,the effect of 0.8m/min on the soil porosity and stress changes around the pile is better.The free blade can effectively fix the displacement of the damaged soil particles,so that the soil particles can be temporarily fixed in the free blade to reduce the disturbance effect on the soil around the pile.(3)The soil displacement in deep soil was observed and recorded by the field test of the micro-disturbed deep mixing pile,and together with the numerical simulation results,the correctness of the particle flow code simulation is demonstrated.In the field test,the variation of construction parameters has a great influence on the soil disturbance around the pile stage,and the soil disturbance caused by construction is generally small,generally within the range of ±2 mm.Conventional inorganic cementing materials,such as cement,do not perform well in the quality of pile formation in engineering cases.New solidifying materials,which are more efficient and conform to the concept of low-carbon development,are needed for deep mixing curing of soft soil.(4)Based on the research and development of deep mixing curing technology of micro-disturbed and low carbon soft soil,the strength recovery of solidified soil becomes the main factor affecting the deformation control after the construction is finished after the cutting and stirring of soil by the micro-disturbed deep stirring drill body.The indoor unconfined compressive strength test of polymer soil-cement solidified with silty clay and silt soil was carried out,and the influence of polymer curing agent on the strength of cement soil-cement was analyzed from the macroscopic point of view.Combined with X-ray diffraction test and electron microscope scanning test,the mechanism of polymer curing agent was revealed from the microscopic point of view.The strength of polymer cement soil is related to soil quality.The content of clay particles in soil particles determines the role of polymeric consolidator.Polymer cement soil can effectively reduce the use of cement on the premise of ensuring the strength of solidified soil,providing a new direction for meeting the conditions such as curing effect and low carbon target.