陕北两种筑坝土料渗透破坏机理的对比试验研究
发布时间：2018-11-07 06:52
【摘要】：为了解决陕北淤地坝渗透破坏的问题,本次试验以陕北地区淤地坝中粉质壤土和砂质壤土两种常用筑坝土料为研究对象,通过自制渗透变形仪模拟渗透破坏发展过程,计算临界水力坡降,运用激光粒度仪、电子显微镜等仪器探究渗透破坏的微观的发生发展过程,对渗透破坏机理进行研究,为现场筑坝及损坏坝的修复提供理论支持与依据。本论文主要的结论有:(1)筑坝土料试样渗透破坏的临界水力坡降与破坏过程的结论1)根据室内渗透变形试验得出,中粉质壤土在压实度为1.50g/cm3、1.55g/cm3和1.60g/cm3的临界水力坡降分别为3.28、4.68和6.78;砂质壤土在压实度为1.50g/cm3、1.55g/cm3和1.60g/cm3的临界水力坡降分别为2.28、3.38和4.18;2)在相同的压实度下,中粉质壤土的临界水力坡降高于砂质壤土,但渗流排水效果远差于砂质壤土,颗粒级配上中粉质壤土的连续性好于砂质壤土,渗透破坏的时间上砂质壤土远大于中粉质壤土;3)对于同种筑坝土样,临界水力坡降和渗流速度与压实度均成线性相关关系,压实度越大,临界水力坡降越大,抗渗性能越好。(2)试验土样分层探求渗透破坏发展规律结论对于中粉质壤土试验土样中,第三层土样即整体的中下游位置及第四层土样即整体试样的下游位置最容易发生渗透破坏变形。对于砂质壤土而言,第四层土样即下游处容易出现断层,发生渗透破坏。(3)渗透破坏试样的微观研究结论1)在同种压实度下,中粉质壤土的颗粒平均直径与孔隙率整体均大幅度小于砂质壤土;孔隙平均直径略小于同压实度下的砂质壤土;粒径圆度与砂质壤土差别不大;2)在同种筑坝土料试验中,压实度1.60g/cm3下的试样孔隙率和孔隙平均直径均小于压实度1.50g/cm3的试样,但颗粒平均直径和颗粒圆度相比差别不大;3)在同种筑坝土料同压实度情况下,中粉质壤土其土柱由下至上层土样的颗粒平均直径与孔隙率均呈现递减趋势,但10-15cm层小于15-20cm层;孔隙平均直径均呈现增大趋势。砂质壤土其土柱由下至上层土样的颗粒平均直径和孔隙率均呈现递减趋势;孔隙平均直径均呈现增大趋势。两种土料的粒径圆度的变化趋势均不明显。(4)渗透破坏泥沙颗粒组成结构分析结论1)对于同一种筑坝土料,在不同的压实度下,渗透破坏产生的渗流泥沙的颗粒级配变化不大;2)对于在相同压实度下两种筑坝土料的渗透破坏产生的渗流泥沙对比,中粉质壤土试样中渗流泥沙的颗粒级配中小颗粒组成比例大于砂质壤土;3)对于同种土料渗透破坏过程中产生的渗流泥沙前中期后期的对比,中粉质壤土试样随着渗透破坏的发生,渗流泥沙的粒径组成由小逐渐向大的趋势发展;砂质壤土在渗透破坏的过程中前期以小颗粒为主,中期与后期颗粒级配与粒径比例差别不大。
[Abstract]:In order to solve the problem of seepage failure of silt dam in northern Shaanxi, this experiment takes silty loam and sandy loam in silt dam as the research object, simulates the process of seepage destruction through self-made osmotic deformator. In order to provide theoretical support and basis for site damming and damage dam repair, the critical hydraulic gradient is calculated, and the microscopic development process of seepage failure is explored by means of laser particle size meter and electron microscope, and the mechanism of seepage failure is studied. The main conclusions of this paper are as follows: (1) the conclusion of critical hydraulic slope and failure process of seepage failure of damming soil sample. 1) according to the indoor seepage deformation test, The critical hydraulic gradient of medium silty loam with compaction of 1.50 g / cm ~ 3 and 1.60g/cm3 of 1.55 g / cm ~ 3 and 1.60g/cm3 is 3.284.68 and 6.78, respectively. The critical hydraulic slope of sandy loam with compaction of 1.50 g / cm ~ 3 and 1.60g/cm3 of 1.55 g / cm ~ 3 and 1.60g/cm3 is 2.28 ~ 3.38 and 4.18, respectively. 2) under the same compaction degree, the critical hydraulic gradient of medium silty loam is higher than that of sandy loam, but the effect of seepage drainage is much worse than that of sandy loam, and the continuity of medium silty loam with grain gradation is better than that of sandy loam. The infiltration time of sandy loam is much larger than that of medium silt loam. 3) for the same kind of dam soil samples, the critical hydraulic gradient and seepage velocity have linear correlation with compaction degree. The greater the compaction degree, the greater the critical hydraulic gradient. The better the impermeability is. (2) the delamination of soil samples and the development of seepage failure conclusion for the test soil samples of medium silty loam, The third layer of soil sample is the middle and lower reaches of the whole and the fourth layer of soil sample is the downstream position of the whole sample. For sandy loam soil, the fourth layer of soil sample, that is, the lower reaches of the fault prone to occur permeability damage. (3) the microscopic study of permeability failure specimen conclusion 1) under the same compaction degree, The average particle diameter and porosity of medium silty loam are smaller than those of sandy loam. The average pore diameter is slightly smaller than that of sandy loam under the same compaction, and the diameter roundness is not different from that of sandy loam. 2) in the same dam soil test, the porosity and average pore diameter under compaction degree 1.60g/cm3 are smaller than those with compactness 1.50g/cm3, but the difference between particle average diameter and particle roundness is not significant; 3) under the same compaction degree of the same dam soil, the average particle diameter and porosity of the soil column of the medium silty loam soil from the bottom to the upper layer show a decreasing trend, but the 10-15cm layer is smaller than the 15-20cm layer, and the average pore diameter of the medium silty loam soil tends to increase. In sandy loam, the average particle diameter and porosity of the soil column from the bottom to the upper layer are decreasing, while the average pore diameter is increasing. The variation trend of particle diameter roundness of the two kinds of soil materials is not obvious. (4) the structure analysis of permeable destruction sediment particles. 1) for the same kind of damming soil material, under different compaction degree, The particle gradation of seepage sediment caused by seepage failure has little change. 2) for the comparison of seepage and sediment produced by seepage failure of two kinds of damming soil under the same compaction degree, the proportion of particle gradation of medium silty loam is larger than that of sandy loam. 3) for the comparison of the seepage sediment produced in the same soil material during the process of seepage destruction, the particle size composition of the medium silt loam developed gradually from small to large with the occurrence of seepage failure. In the early stage of permeation failure of sandy loam soil, the small particles are dominant, and the difference of particle gradation and particle size ratio between the middle and late stages is not significant.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV41
本文编号：2315551
[Abstract]:In order to solve the problem of seepage failure of silt dam in northern Shaanxi, this experiment takes silty loam and sandy loam in silt dam as the research object, simulates the process of seepage destruction through self-made osmotic deformator. In order to provide theoretical support and basis for site damming and damage dam repair, the critical hydraulic gradient is calculated, and the microscopic development process of seepage failure is explored by means of laser particle size meter and electron microscope, and the mechanism of seepage failure is studied. The main conclusions of this paper are as follows: (1) the conclusion of critical hydraulic slope and failure process of seepage failure of damming soil sample. 1) according to the indoor seepage deformation test, The critical hydraulic gradient of medium silty loam with compaction of 1.50 g / cm ~ 3 and 1.60g/cm3 of 1.55 g / cm ~ 3 and 1.60g/cm3 is 3.284.68 and 6.78, respectively. The critical hydraulic slope of sandy loam with compaction of 1.50 g / cm ~ 3 and 1.60g/cm3 of 1.55 g / cm ~ 3 and 1.60g/cm3 is 2.28 ~ 3.38 and 4.18, respectively. 2) under the same compaction degree, the critical hydraulic gradient of medium silty loam is higher than that of sandy loam, but the effect of seepage drainage is much worse than that of sandy loam, and the continuity of medium silty loam with grain gradation is better than that of sandy loam. The infiltration time of sandy loam is much larger than that of medium silt loam. 3) for the same kind of dam soil samples, the critical hydraulic gradient and seepage velocity have linear correlation with compaction degree. The greater the compaction degree, the greater the critical hydraulic gradient. The better the impermeability is. (2) the delamination of soil samples and the development of seepage failure conclusion for the test soil samples of medium silty loam, The third layer of soil sample is the middle and lower reaches of the whole and the fourth layer of soil sample is the downstream position of the whole sample. For sandy loam soil, the fourth layer of soil sample, that is, the lower reaches of the fault prone to occur permeability damage. (3) the microscopic study of permeability failure specimen conclusion 1) under the same compaction degree, The average particle diameter and porosity of medium silty loam are smaller than those of sandy loam. The average pore diameter is slightly smaller than that of sandy loam under the same compaction, and the diameter roundness is not different from that of sandy loam. 2) in the same dam soil test, the porosity and average pore diameter under compaction degree 1.60g/cm3 are smaller than those with compactness 1.50g/cm3, but the difference between particle average diameter and particle roundness is not significant; 3) under the same compaction degree of the same dam soil, the average particle diameter and porosity of the soil column of the medium silty loam soil from the bottom to the upper layer show a decreasing trend, but the 10-15cm layer is smaller than the 15-20cm layer, and the average pore diameter of the medium silty loam soil tends to increase. In sandy loam, the average particle diameter and porosity of the soil column from the bottom to the upper layer are decreasing, while the average pore diameter is increasing. The variation trend of particle diameter roundness of the two kinds of soil materials is not obvious. (4) the structure analysis of permeable destruction sediment particles. 1) for the same kind of damming soil material, under different compaction degree, The particle gradation of seepage sediment caused by seepage failure has little change. 2) for the comparison of seepage and sediment produced by seepage failure of two kinds of damming soil under the same compaction degree, the proportion of particle gradation of medium silty loam is larger than that of sandy loam. 3) for the comparison of the seepage sediment produced in the same soil material during the process of seepage destruction, the particle size composition of the medium silt loam developed gradually from small to large with the occurrence of seepage failure. In the early stage of permeation failure of sandy loam soil, the small particles are dominant, and the difference of particle gradation and particle size ratio between the middle and late stages is not significant.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV41
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