Study On Engineering Characteristics And Similar Materials Of Peaty Soil Deposited In Plateau Lake Facies

The lake area of the Yunnan Plateau is rich in peat soil.To understand the engineering characteristics of peat soil in Dianchi Basin more comprehensively and profoundly and improve the safety of deep foundation pit engineering in the peat soil stratum,it is necessary to carry out targeted experimental research on its physical and mechanical properties.In addition,the model test research method can intuitively observe the displacement and internal force of rock,soil,and structures.It has been widely used in the research of foundation pit engineering,and an essential part of the similar model test is to find similar suitable materials.So far,the research work on similar materials at home and abroad is mainly aimed at rocks.In contrast,there is little research on developing similar materials,especially for peat soil similar materials.There are almost no mature research results for reference.Based on this,this paper summarizes peat soil’s physical and mechanical indexes by consulting many kinds of literature and carries out consolidation-permeability tests and static lateral pressure coefficient tests for permeability coefficient and static lateral pressure coefficient to further improve the physical and mechanical properties of peat soil.At the same time,combined with the essential physical and mechanical characteristics of peat soil in Dianchi Basin,the ratio test of peat soil similar to materials was carried out by orthogonal test design.The sensitivity and significance of the main indexes in the orthogonal test results were analyzed using the range and variance methods.Combined with the comprehensive balance method,the components and reasonable blending ratio of raw materials of similar peat materials were preliminarily proposed.The main research contents and conclusions are as follows.（1）Through literature research,the variation range of physical and mechanical indexes of peat soil in Dianchi Basin is summarized,and the indexes needed in this paper are summarized.The density is concentrated in 0.90 to 1.61g/cm³,the range of cohesion is 6.70 to 25.83k Pa,and the range of internal friction angle is 4.10 to 17.90°.（2）The consolidation-permeability test of peat soil in Dianchi Basin was carried out by using a single lever consolidation instrument.The test results show that the permeability coefficient of peat soil is greatly affected by the consolidation pressure,that is,it decreases first and then stabilizes with the increase of consolidation pressure,and decreases exponentially with the compression modulus,but the relationship with the compression coefficient is not obvious.The variation range of the permeability coefficient of peat soil is 6.81×10^-5 to 2.79×10^-4cm/s,and it is found that the permeability coefficient of peat soil can be calculated by lg（1+e）-lgk_v permeability model,and it has high applicability,which further deepens the understanding of peat soil in Dianchi Basin.（3）The static lateral pressure coefficient test of peat soil in Dianchi Basin was carried out by the K₀ consolidation instrument.The test results show that the static lateral pressure coefficient of peat soil decreases exponentially with the void ratio,increases linearly with the specific gravity,and decreases linearly with the organic matter content.The static lateral pressure coefficient of peat soil varies from 0.46 to 0.68.（4）Raw materials were fly ash,bentonite,ash calcium powder,lignin,and water.An orthogonal test design was carried out with fly ash,bentonite,ash calcium powder,and ash calcium powder lignin as the primary control factors.Four factors and levels were designed,and16 proportioning schemes were designed.Each group was tested for specific gravity,density,permeability coefficient,static lateral pressure coefficient,and shear strength.The test results show that the physical and mechanical properties of peat soil similar to materials under different mix ratios can meet the requirements of peat soil similar to materials.The range method carried out the sensitivity analysis of the physical and mechanical properties of the orthogonal test results.The results showed that the amount of lime calcium powder and lignin greatly influenced the specific gravity and density index.The mixing amount of bentonite and lime calcium powder significantly influences the static side pressure coefficient;the blending amount of lignin and fly ash significantly regulates the compression coefficient,compression modulus,permeability coefficient,and cohesion.The amount of lignin and bentonite is the most influential factor on the internal friction angle.Through the analysis of variance of the influence degree of each factor,the primary and secondary order of the influencing factors of peat soil similar materials is lignin（D）,fly ash（A）,bentonite（B）,lime-calcium powder（C）.（5）According to the results of the primary and secondary factors,a reasonable ratio analysis is carried out with the comprehensive balance method.The reasonable combination scheme of peat soil similar materials is A₂B₂C₁D₄.The reasonable mixing ratio is 12%of fly ash,8%of lime calcium powder,5%of bentonite,and 30%of lignin.Through the verification and analysis of the reasonable ratio scheme of peat soil similar materials,the measured physical performance index and mechanical performance index meet the range required by each physical and mechanical index of peat soil,and the reasonable reliability of the ratio scheme is verified.According to this verification result,the reasonable ratio of peat soil to similar materials can be improved appropriately.