| With the rapid development of China's economy,the large-scale development of northwest China and the implementation of One Belt And One Road,higher requirements are put forward for the operation capacity of railway,especially high-speed railway and other transportation industries.Represented by qinghai of high-speed rail,highways built in saline soil area,the railway running speed is slow,generally don't do special handling in saline soil area,and now the railway speed running ability is higher and higher,also means that the project design and construction difficulty is more and more big,the improvement of operation means that must carry on the corresponding processing in saline soil area,in order to meet the deformation of railway standard.From the perspective of regional geological structure,the railway from xitieshan to north hoboxun salt lake mine in qinghai province has a wide range of sulfuric acid soil and frequent precipitation.The soil is in a state of constant saturation,and the salt-saturated sand soil will have liquefaction effect under the action of earthquake,resulting in roadbed instability,collapse and other engineering disasters.Therefore,it is of great practical significance to study the factors affecting the liquefaction characteristics of saturated sand soil,and to serve the engineering construction.Because of the influence factors of saline soil is more,for the liquefaction characteristics of saturated sandy soil containing salt,soil without a more comprehensive system of research,so this article relying on the solder iron mountain in qinghai province to the north of salt lake mining area railway huo cloth engineering characteristics,through indoor soil test have unearthed basic sample,the optimum moisture content,content of soil salt content.Then the soil samples were remolded to prepare five kinds of saturated sand soils: no soil,10 soil,20%soil,30% soil and 40% soil.And prepare five kinds of saturated sand soil with no salt,3% salt,5% salt,8% salt and 10% salt,and conduct the GDS indoor dynamic triaxial liquefaction test.Is obtained by testing the stress and strain curves of different soil,pore pressure curve,dynamic shear stress ratio curve,dynamic shear stress and strain hysteresis curve,dynamic shear modulus and damping ratio characteristic curve,and finally verified by the data analysis of salt is put forward,including soil saturated sand the correctness of the judgment standard,finally combining with ANSYS numerical simulation software,simulation of different sulfate content and saturated sand under different content of fine grained soil roadbed model,analysis of the settlement and displacement under seismic load Y stress change rule of the main research contents and results are as follows:(1)this paper analyzed the soil,salt saturated sand liquefaction mechanism,with soil,salt saturated sandy soil liquefaction is pointed out that the particularity of,at the same time,through access to information on the existing criteria of salt is put forward,including soil saturated sand epsilon(d)two-way strain amplitude reaches 5% began to liquefaction,and its rationality was verified in subsequent tests.(2)the parameters of excavated samples were obtained through indoor basic geotechnical test,and the dynamic triaxial test was designed.Based on different soil content,salt content dynamic triaxial test for soil samples,stress and strain curve comparison of five kinds of saturated sandy soil in different soil content stress and strain time history curve,get with the increase of clay content,increase the axial stress is not the law of soil and the soil saturated sand damage length is greater than does not contain saturated sand soil.By comparing the stress and strain time-history curves of five saturated sandy soils with different salt content,the length of failure time required for the non-salt saturated sandy soil is obtained,and the failure time required for the salt saturated sandy soil is longer.(3)the pore pressure(a)curve of saturated sandy soil with salt and soil showed that the pore pressure(a)curve had an effect on the pore pressure curve of sandy soil under different contents of sulfate and fine grain soil.Generally speaking,when the pore pressure is stable,the maximum pore pressure of saturated sand soil with soil is higher than that of saturated sand soil without soil.The maximum pore pressure of saturated sandy soil with salt is higher than that of saturated sandy soil without salt.(4)by analyzing the CSR curves of different soils,it is found that the larger the CSR is under the same confining pressure(100kPa),the stronger the anti-liquefaction ability is.By comparing the CSR-vibration N curve of the dynamic shear stress ratio,it is found that the dynamic shear stress ratio increases linearly with the increase of soil and salt content.At the same time,it also shows that the anti-liquefaction performance of two kinds of soils increases under different soil and salt content.Applied to the actual engineering,that is,the liquefaction of the land can be through the above method to improve the anti-liquefaction performance.(5)through the analysis of the shear stress-strain hysteretic curve of the sample,it is found that the area of the hysteretic curve is related to the curve shape.Soil due to the vibration of vibration frequency is less than the initial vibrations is liquefied yes,including sulfate saturated sand and fine grained soils saturated sandy soil liquefaction in the initial stage,lead to the stress and strain curve changes in small scope,when containing sulfate saturated sandy soil,the vibration of the fine grained soil saturated sand began to increase,its up to the two initial liquefaction of soil vibration frequency,the vibration load of formationdamage is more than two kinds of soils,soil liquefaction reaction.So the area of the hysteretic curve increases accordingly.(6)as a result of the fine grained soil content in the soil increased,lead to the shear resistance ability has been increased,so when the process of fine grained soil increases,the maximum shear modulus of soil is increased,so that contains fine grained soil shear modulus maximum value of saturated sand content of the fine grained soils in saturated sandy soil is directly proportional to the relationship.Due to sulfate content in the soil increased from 0 to8%,as the grow in quantity of sulfate content,led to its liquefaction resistance also increase,when continue to add in the soil sulfate content reaches 10%,the shear modulus is less than8% of shear modulus,that result when sulfate content is 8%,reached the maximum shear modulus of soil,the soil and the dynamic shear modulus is not increased with the increase of sulfate content continues to increase(7)build soil,salt in different saturated sandy soil roadbed fill after processing model,impose concentrated on sandy soil roadbed model seismic waves,found that when adding sulfate and fine grained soil,the soil displacement of the two different types of saturated sandy soil subgrade in varying degrees of smaller,and two kinds of saturated sand in the Y direction of the maximum stress also increased in varying degrees,so that when the sulfate is added to the soil,and fine grained soils,the liquefaction resistance of saturated sandy soil than pure sand effect is more apparent,and achieved the effect of resisting earthquake liquefaction. |
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