| The loess is the accumulation of aeolian deposits in the Quaternary period,and many typical loess-paleosol profile have been formed in the northwestern of China after millions years of deposition.With the implementation of the strategy for the rise of western China,the highway construction has been greatly developed in these regions,the high fill embankments and deep cutting slop also appeared,which involves the physical and mechanical properties of deep loess and ancient soil,such as strength and deformation.At present,there are few studies on the profile characteristics of loess-paleosols sequences,and its regular pattern is difficult to grasp.Based on this,it is of practical significance to research the physical and mechanical properties of the serial sections of loess-paleosol profile.Base on typical loess-paleosol profile in Shijiazhuang in Luochuan,this paper studied the grain-size composition and compression characteristics of each soil layer systematically by means of routine soil test,particle analysis test and consolidation test.And compared the compression characteristics of loess-paleosol profile in Wutian in Weinan and Kongjiayuan in Xifeng.The main contributions are as follows:(1)In terms of particle composition,the grain size of each layer is mainly coarse silt,the clay and fine particles are followed,the content of fine sand is the least.The particle content of layers is also different,the content of clay and fine particles of loess layer is smaller than that in paleosol,and the content of coarse silt is greater than it.The optimum moisture content of the section is near 13%,the average maximum dry density is 1.91g/cm~3,both fluctuate along the depth of the profile.(2)Base on the Fractal theory,the particle sizes of each layer have a good fractal characteristic with the cumulative throughput of limit size,the fractal dimension D is between2.4214 and 2.7715.D is positively correlated with the content of clay and fine particles,and negatively correlated with the content of coarse silt and fine sand.In addition,The specific surface area of soil increases with D,the median diameter decreases with D.Both the non-uniform coefficient and the curvature coefficient tend to increase first and then decrease with the change of the fractal dimension D,and reach the maximum when D is about 2.6.(3)Through the consolidation test,it was found that the compression modulus fluctuates along the depth of the profile,and its crest appears mainly in the paleosol S;The compression modulus increases with the degree of compaction,and compressibility decreases with the compaction.In addition,the compressibility and compressive modulus of soil samples have different change with the degree of compaction at different moisture contents.When the moisture content exceeds the optimum moisture content,the change is significant.And the moisture content has the greatest impact on the compression characteristics,the compaction degree is the smallest.(4)Comparing with the compression characteristics of profile in the Luochuan,the Weinan,and the Xifeng,it was found that the compressive modulus in Luochuan is the smallest,and the largest in Xifeng for the loess layer L,and the compressive modulus decreases from south to north and increases from east to west.For the paleosol layer,the compression modulus in Weinan is the smallest,and the largest in Kongjiayuan,and it increases from south to north and from east to west.But the difference of compressive modulus for the three regions is little in the same geological period. |
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