| Peat soil(general designation of peat and peaty soil)mainly includes undecomposed fiber,semi-decomposed fiber,humus and minerals,which are formed under natural sedimentation.Due to the influence of sedimentation,the arrangement of the material components has obvious direction and shows the characteristic of anisotropy.The accuracy and rationality of engineering calculations need to consider the influence of anisotropy.At present,the study on the anisotropy of peat soil at home and abroad is mostly directed to the low-decomposing peat soil,and there are few studies on the engineering properties of high-decomposing peat soil.The peat soils in the Yunnan Plateau are mostly high-decomposing peat soils,which contain a small amount of residual fibers.It is necessary to carry out special study on the anisotropic properties and mechanism of the engineering properties.In this paper,the high-decomposing peat soil in the Dianchi Lake area of Yunnan Plateau is taken as the study object,and its organic matter content,material composition and microstructure characteristics are measured.It is studied by compression test,direct shear test and permeability test.The inherent anisotropy characteristics are discussed from the perspective of analyzing the special components of peat soil.The inherent anisotropy law and mechanism of the engineering properties of plateau peat soil are obtained.The specific study contents and conclusions are as follows:(1)Peat undisturbed soil is taken from typical engineering sites in Kunming where the organic matter content is low,medium and high,and the basic physical properties is determined,and the mineral composition and the microstructure characteristics of soil samples are analyzed by X-ray technique and electron microscopy analysis.The results show that the peat soil has high organic matter content,and most of them belong to high-decomposing peat soil.The basic structural unit is mainly the overhead structure formed by residual fiber and humus-cohes aggregate.(2)The undisturbed peat soil of the plateau lacustrine is sampled at the horizontal,45°,and vertical directions of the sedimentary surface,and a one-dimensional consolidation test is performed using a conventional consolidationinstrument.The test results show that the compressibility of the high-decomposing peat soil in the 45 direction to the deposition surface is higher than that in the horizontal and vertical directions under lower consolidation pressure.However,with the increase of consolidation pressure,the anisotropy of compression deformation caused by different cutting angles gradually disappears.(3)The shear strength of peat soil in different sampling directions is measured by direct shear test,and the anisotropy of shear strength of peat soil was analyzed.The results show that the shear strength of high-decomposition peat soil in vertical direction is higher than that in horizontal direction,and the strength in the 45 direction is greater than that in horizontal direction,and the strength anisotropy is weaker.The effect is mainly reflect in cohesion,the effect of internal friction angle is small,and the degree of anisotropy of shear strength is related to the content of organic matter.(4)The permeability coefficient of peat soil at three angles is measured by permeation instrument.The results show that the permeability coefficient of high-decomposition peat soil has a certain correlation with the cutting angle,showing a law that the permeability coefficient increases with the increasing of cutting angle.When the organic matter content is "moderate",the permeability anisotropy is most obvious.(5)The arrangement and regularity of components in the formation process of peat soil is analyzed.The results show that the anisotropy mechanism of peat soil is complex,and the mineral soil particles,humus and residual fibers have different effects in terms of anisotropic effect. |
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