| Peat soil(collectively known as peat and peaty soil)is a special soft soil formed in rivers,lakes,sedimentary plains and mountain valleys by the long-term geological processes and complex biochemical processes of plant residues in a specific environment.The geological soil layer of yunnan kunming lake and Dali lake belongs to the typical plateau lacustrine peat soil and is one of the few cities with deep peat soil in the urban area.At present,the research on typical peaty soil dynamic characteristics in yunnan is less,is now a few scholars of yunnan kunming dianchi lake region of peat soil to study the dynamic characteristics,due to the geotechnical engineering has a strong regional,so show the regionalization research focus,geotechnical engineering research of yunnan Dali erhai lake region typical plateau lake facies peat soil dynamic characteristics research has important significance.GDS dynamic triaxial instrument was used in this paper to study the dynamic characteristics of test soil samples.The main work and conclusions of this paper are as follows:(1)Under various control conditions(confining pressure,consolidation ratio and frequency)and under progressive loading,the hysteretic loop is relatively closed,with narrow two segments presenting a sharp leaf shape and a "long fusiform"overall.The change characteristics of quantitative parameters such as the slope,center offset and area of the long axis are mapped from the evolution law of the hysteretic loop;(2)Under various control conditions(confining pressure,consolidation ratio(within the range of critical consolidation ratio)and frequency),as the amplitude of dynamic stress under progressive loading increases,the approximate logarithmic function of slope declinates continuously,and the approximate exponential function of center offset and area increases.The higher the confining pressure and consolidation ratio is,the higher the slope is.The influence of frequency on slope is relatively complex.In general,the lower the frequency is,the faster the overall attenuation rate of slope is,that is,the faster the attenuation rate of stiffness and elastic property is.The larger the confining pressure and frequency are,the smaller the center offset is,the smaller the residual plastic deformation and mesoscopic damage are;conversely,the larger the consolidation ratio is,the larger the center offset is,the larger the residual plastic deformation and mesoscopic damage are.The larger the confining pressure,consolidation ratio and frequency are,the smaller the area value is;(3)Dynamic strain and dynamic stress show a nonlinear growth relationship.The larger the confining pressure and consolidation ratio(within the range of critical consolidation ratio),the greater the dynamic strength of soil and the greater the stiffness,the smaller the deformation of soil and the smaller the dynamic deformation of soil.The lower the frequency is,the more complex the change is due to the rate effect;(4)Dynamic elastic modulus and dynamic strain show a nonlinear attenuation relationship,and the attenuation rate of dynamic elastic modulus changes from rapid to relatively gentle to relatively stable.The higher the confining pressure,consolidation ratio(within the critical consolidation ratio range)and frequency,the greater the dynamic elastic modulus,indicating that peat has a stronger ability to resist elastic deformation;(5)The normalized fitting of dynamic elastic modulus presents a linear relationship,indicating that peaty soil is suitable for the"H-D"model for the fitting.The larger the confining pressure,consolidation ratio(within the critical consolidation ratio range)and frequency,the smaller the dynamic constitutive parameters are,that is,the smaller the linear intercept is,indicating the larger the maximum dynamic elastic modulus is.Similarly,the smaller the dynamic constitutive parameters are,that is,the smaller the linear slope is,indicating the greater the maximum dynamic stress is,the regression fitting equation of maximum dynamic elastic modulus,confining pressure and consolidation ratio is established:(6)Dynamic shear modulus and dynamic shear strain show a nonlinear attenuation relationship,that is,with the increase of dynamic shear strain,the dynamic shear modulus decreases.The larger the confining pressure and consolidation ratio(within the critical consolidation ratio),the larger the dynamic shear modulus.The effect of frequency on the dynamic shear modulus of peat soil is relatively complex and the effect of rate effect is relatively complex;(7)The ratio of dynamic shear modulus decreases with the increase of dynamic strain,the distribution of fitting points is relatively concentrated and discrete,and the fitted normalized curve is relatively good,indicating that peaty soil is suitable for the fitting of hardin-drnevich hyperbola model.However,with the increase of confining pressure and consolidation ratio(within the critical consolidation ratio range),the trend of dynamic shear modulus ratio increasing is relatively insignificant,and the influence of frequency on dynamic shear modulus ratio is relatively complex.It indicates that the confining pressure,consolidation ratio and frequency have no obvious tendency to attenuate the dynamic shear modulus ratio,that is,the dynamic shear modulus ratio is relatively less sensitive to the variation of confining pressure,consolidation ratio and frequency;(8)The damping ratio and the dynamic shear strain show a nonlinear growth relationship,and the influence of confining pressure on the damping ratio is relatively complex.As the confining pressure increases,the damping ratio first decreases and then increases.The damping ratio increases with the consolidation ratio(within the critical consolidation ratio range).Frequency has a tendency to affect the damping ratio,and its sensitivity is obviously stronger than the confining pressure and consolidation ratio.The lower the frequency is,the greater the damping ratio is,indicating that peat soil is very sensitive to the rate effect in the process of progressive loading. |
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