Experiment And Technology Research Of Carbonized Composite Pile Based On Permeable Pipe Pile

The disadvantage of cement as soil solidifying material is that it produces a large amount of carbon emissions.Reactive MgO can achieve good curing effect after carbonization,and realization of carbon cycle,which has high environmental benefits.Therefore,it is an effective cement substitute.Based on the existing research results of MgO carbonization method from Institute of Geotechnical Engineering,Southeast University,the technology of carbonized composite pile based on permeable pipe pile was first put forward.Laboratory unit cell test,model test and field single-point test were carried out.The feasibility of this method is verified.The main contents and conclusions were drawn as follows:?1?The permeability characteristics of reactive MgO-carbonized silt and silty clay were systematically studied by using the triaxial flexible wall chamber permeability test.It was found that the permeability coefficient of the soil after carbonization was in the order of magnitude of10^-510^-6cm/s.The permeability coefficient of reactive MgO-stabilized soils decreases with the increase of MgO content.It is in the same order of magnitude compared with PC-treated soil with the same curing agent content.The permeability coefficient of carbonated silt is obviously larger than that of carbonated silty clay.When both the MgO-stabilized silt and silty clay are carbonized for 6.0 hours,the corresponding permeability coefficient could reach the minimum(10^-6cm/s).Ventilation pressure has little effect on the permeability coefficient of carbonated reactive MgO-stabilized soils.?2?Through the laboratory test,it is proved that the carbonization method of the permeable pipe pile can achieve the carbonization effect basically similar to that of the three-axis closed carbonization.Within the effective influence range of the permeable pipe pile,the carbonation effect of soil stirred at different distances is basically the same.With short carbonation time or small carbonation ventilation pressure,near carbonation effect is better.The carbonization process is beneficial to the strength growth of the permeable pipe pile.After 6 hours,it can reach 1.6 times of the initial strength.?3?The application of carbonization method of permeable pipe pile in silt and silty soil was studied through laboratory model test.The carbonization effect was evaluated by temperature,physical and mechanical properties.The results show that sufficient time for MgO to be hydrated before carbonization should be guaranteed.The carbonization effect using permeable pipe pile on mixed soil at different depths is basically the same.Due to soil particles,moisture and the uncertainty of gas movement direction,there are effective and maximum carbonization distances in this method.In this research,the effective carbonization distance can reach at least 40 cm under the ventilation pressure of 200 kPa.?4?Based on the laboratory test and field single point test,the characteristics of different reaction stages of carbonization method of permeable pipe pile are summarized.The site construction technology of carbonization method of permeable pipe pile is put forward preliminarily.