| Soil creep is one of the main causes of post-construction settlement.Peat soil has high moisture content,high organic matter,large pore ratio,low strength and permeability,which makes the creep characteristics of peat soil different from that of general soft clay.Although there are some studies on the rheological properties of organic soil at home and abroad,due to the differences of sedimentary environment,geographical environment and climatic conditions of peat soil,peat soil has a strong regional,so it is necessary to study and analyze the creep characteristics of lake sedimentary peat soil.The sediments of Dianchi Lake are thick and multi-layered.Completed Because of the creep characteristics of peat soil,the post-construction settlement is too large and the building can not be used normally,so there are serious safety risks.The peat soil under different buried depth in the site of Dianchi Convention and Exhibition Center and Jinhui Center in the area near Dianchi Lake Kunming was studied.the nonlinear creep model and compressive consolidation characteristics of peat soil were systematically analyzed by sampling analysis,indoor geotechnical test,microstructure test(SEM)and energy spectrum test(EDS)of peat soil.The main research contents are as follows:(1)Based on the collected geological prospecting data and related literatures,the characteristics of peat soil which is different from ordinary soft clay are analyzed from the formation reason,necessary condition and deposition process of peat soil,and the variation law of basic physical and mechanical properties index with soil depth is analyzed.The stress history of peat soil has great influence on the compression characteristics of peat soil.The pre-consolidation pressure and ln pressure of peat soil were analyzed from peat soil e-logp、ln(1e)-lgp and ln(1e)-(1p)the effect of stress history on the compression properties of soil.(2)Compression index,consolidation coefficient and consolidation degree of five layers of peat soil with different buried depth were obtained from the compression curve and S-lgt curve.Compression and consolidation characteristics ofolded soil and undisturbed soil was compared and analyzed,and the difference of microstructure of same layer peat soil was compared.(3)The time-history curves and equal-time curves of stress and strain were obtained according to the creep tests of peat soil under different site standards Line,e-lgt curve,lnε-lnt curve to analyze the creep characteristics of peat soil.The creep process characteristics of peat soil were analyzed from stress-strain time-history curve,the variation law of sub-solid node,sub-consolidation coefficient,stress,strain and pore ratio of peat soil was analyzed by single-logarithmic curve and double-logic curve.(4)A nonlinear creep constitutive model of peat soil was established at macroscopic level to analyze the creep characteristics of peat soil.The theoretical model is carried out by introducing the nonlinear instantaneous elastic modulus of soil nonlinear correction,so that the linear theoretical model can consider the nonlinear characteristics of soil.By analyzing the functional relationship between theoretical model parameters and stress σ,the constitutive equation of strain,stress and time of peat soil is established.(5)The nonlinear creep characteristics of soil are well described.In order to consider the time-effect hardening model,an empirical model of the time-effect nonlinear power function is established based on the creep data of peat soil.The creep behavior of peat soil is related to its stress,from the power function empirical model parameters and stress The relationship analysis shows that there is a functional relationship between the parameter a0、m and the stress σ,so the empirical model of power function about stress,strain and time is obtained. |
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