渠基土室内换填冻胀试验

Experimental Study on Frost Heaving of Channel Foundation Soil by Indoor Replacement Filling

渠基土换填法是目前有效减小渠道冻胀破坏的方法之一,选取合理换填材料与换填深度是有效控制渠道冻胀破坏的关键。目前换填法研究更多的是采用有限元软件对渠基土换填进行分析,而相关的室内试验较少。以沈阳市浑浦灌区粉质黏土为研究对象,选取砂砾料和粉细沙作为换填材料,对渠基土进行30,50,70,90,110mm 5种深度换填,进行室内单向冻结试验。在初始温度相同条件下,观测不同换填条件下土样的冻胀变形量、内部温度和冻结速率等变化特点。结果表明:相同土柱高度时,换填前后土样内部各点温度随时间关系曲线均呈“S”型分布,换填砂砾料与粉细砂分别使土样的起始冻结时间提前2.0h和1.3h,均会缩短土样冻结历时,分别缩短4.0h和2.0h,降低土样冻胀量,不同材料相同换填深度时,砂砾料削减冻胀量效果好于粉细沙,换填70mm时,2种换填材料冻胀量削减率分别为70.44%和59.85%,同种材料不同换填深度时,冻胀量削减随着换填深度增加。对2种换填材料冻胀量与换填深度关系曲线进行拟合,得出满足防冻胀规范设计标准砂砾料与粉细沙的换填深度分别为81.625mm和111.326mm。在相同冻结历时情况下,对换填深度与冻结深度、渠基土冻结厚度进行拟合分析,结果表明:换填2种材料均会不同程度上增加冻结深度,换填70mm时,2种换填土样的冻结深度分别为16.7457cm和15.2001cm,由于粉细沙的物理性质较砂砾料相比更接近渠基土,故砂砾料对冻深的影响较大;单一从换填后2种换填材料对渠基土冻结厚度方面考虑,换填粉细沙后渠基土冻结厚度要小于砂砾料,削减冻胀量效果好于砂砾料。但由于砂砾料对冻胀量的削减效果好于粉细沙,故2种换填材料对渠基土冻结厚度影响较冻胀量削减对降低渠道冻胀破坏的作用较小。针对渠基土进行换填研究,给出不同换填情况下对渠道冻胀的影响情况,各工程可根据灌区渠基土冻胀特点与实际工程需要采取合理的换填方案。

The replacement method of channel foundation soil is one of the effective methods to reduce the channel frost heaving damage.The key to effectively control the channel frost heaving is to select reasonable replacement materials and replacement depth.At present,the finite element software is used to analyze the replacement method of canal foundation soil,but there are few relevant laboratory tests.In this paper,silty clay in Hunpu Irrigation District of Shenyang was taken as the research object.Sand and gravel materials and silty sand were selected as replacement materials to fill the tunnel foundation soil at 5 depths of 30,50,70,90 and 110mm,and one-way indoor freezing test was conducted.Under the same initial temperature,the changes of frost heaving deformation,internal temperature and freezing rate of soil samples under different refilling conditions were observed.The results showed that:when the height of soil column was the same,the relation curve of temperature at each point in the soil sample before and after filling presented an"S"-shaped distribution with time.The filling of sand and gravel material and fine sand could advance the initial freezing time of the soil sample by 2.0h and 1.3h,which shortens the freezing duration of the soil sample by 4.0h and 2.0h,and reduce the amount of frost heave of the soil sample.When the filling depth of different materials was the same,the effect of sand and gravel material on reducing frost heave was better than that of fine sand.When the filling was changed for 70mm,the reduction rates of frost heave of the two kinds of filling materials was 70.44%and 59.85%.When the filling depths were different for the same material,the reduction of frost heave increases with the filling depth.By fitting the relation curve between the frost heaving amount and the filling depth of two kinds of filling materials,it is concluded that the filling depths of sand and fine sand meeting the design standard of anti-frost heaving were 81.625mm and 111.326mm.In the case of the same freezing duration,the fitting analysis of filling depth,freezing depth and freezing thickness of channel foundation soil was carried out,and the results showed that:When filling 70mm,the freezing depths of the two filling samples was 16.7457cm and 15.2001cm.Since the physical properties of fine sand are closer to the channel foundation soil than that of sand and gravel,the influence of sand and gravel on freezing depth is greater.Considering the freezing thickness of channel foundation soil by the two filling materials,the freezing thickness of channel foundation soil was less than that of sand and gravel,and the effect of reducing frost heave was better than that of sand and gravel.However,the effect of sand and gravel on frost heave reduction was better than that of fine sand,so the effect of two kinds of filling materials on the freezing thickness of channel foundation soil was less than that of frost heave reduction on reducing frost heave damage of channel.Based on the study of replacement of channel foundation soil,the influence of different replacement on channel frost heave was given,and reasonable replacement scheme could be adopted for each project according to the characteristics of canal foundation soil frost heave in irrigation area and actual engineering needs.