【作者】 苏涛；

【导师】 张兴昌；

【作者基本信息】 西北农林科技大学 ， 环境科学， 2011， 博士

【摘要】 由于具有独特的地质地貌和气候特征,砒砂岩地区被喻为“世界水土流失之最”。基于探讨该地区边坡侵蚀规律和EN-1加固边坡效果以提高其边坡冲刷稳定性为目的,采用自然边坡冲刷试验、室内土工试验和人工模拟边坡冲刷试验相结合的研究方法,以该地区边坡冲刷稳定性影响因素的研究为前提,分析了EN-1固化剂对砒砂岩风化土工程力学特性和模拟边坡抗冲性的影响,优选出适用该地区固化边坡的EN-1掺量、养护龄期、压实度和土壤含水量。获得以下进展:1.水流冲刷和坡度是影响砒砂岩自然边坡稳定性的主要因素。径流强度、产沙强度和径流含沙量随冲刷流量的增大而增大,灰黄色砒砂岩的径流强度、产沙强度和径流含沙量随坡度的增大先增大后减小,临界坡度为25°,灰白和红棕色砒砂岩的产流产沙指标随坡度的增大而增大。径流流速随冲刷流量和坡度的增大而增大。在试验设计的冲刷流量和坡度范围内,坡面径流的运动型态均属于层流,当冲刷流量和坡度较小时,坡面径流流态属于缓流,反之,属于急流。灰黄和红棕色砒砂岩的径流阻力系数f随冲刷流量的增大而减小,而灰白色砒砂岩的f随冲刷流量的增大而增大;灰黄色砒砂岩的f随坡度的增大呈现出先增大后减小的趋势,在灰白色和红棕色砒砂岩的f则随坡度的增大而增大。径流剪切力、径流功率和径流动能理论可不同程度解释砒砂岩自然边坡坡面侵蚀的径流产沙过程。径流阻力系数、水力半径、径流功率和径流动能对砒砂岩自然边坡冲刷的侵蚀产沙量的贡献较大。2.植被覆盖可明显增加砒砂岩自然边坡水流冲刷的稳定性。不同植被覆盖类型的砒砂岩自然边坡坡面径流强度大小排序为:裸地>油松>草地>柠条>沙棘;产沙强度和径流含沙量大小排序为:裸地>草地>柠条>油松>沙棘。相对于草地、柠条和油松覆盖的坡面,沙棘覆盖的砒砂岩自然边坡减流和减沙效益均最大。3. EN-1掺量、养护龄期、压实度和土壤含水量是影响EN-1固化土击实、抗剪强度和抗渗能力特征的主要因素。EN-1对砒砂岩风化土最优含水量的影响较小,但能有效提高其最大干密度。砒砂岩素土和固化土的抗剪强度和抗渗能力随压实度的增大而增大,抗剪强度随含水量的增大而减小。随EN-1掺量的增大和养护时间的延长,砒砂岩固化土抗剪强度和抗渗能力均大幅提高。4.水流冲刷、坡度和压实度是影响砒砂岩人工模拟边坡冲刷稳定性的主要因素。坡面径流强度随冲刷流量和压实度的增大而增大,坡度对其没有显著影响。产沙强度和径流含沙量随冲刷流量的增大而增大,随压实度的增大而减小,随坡度的增大先增大后减小,黄绿和灰黄色砒砂岩坡面的临界坡度分别为60°和50°。径流流速随冲刷流量、坡度和压实度的增大而增大。当冲刷流量较大和压实度较小处理的冲刷后期,坡面径流的运动型态属于紊流外,其它处理均属于层流;除压实度较小处理的冲刷后期坡面径流的流态为缓流外,其余处理均属于急流。f随冲刷流量的增大而增大,随压实度的增大而减小;黄绿色砒砂岩的f随着坡度的增大有先增大后减小的趋势,而灰黄色砒砂岩的f随坡度的变化趋势正好相反。径流剪切力、径流功率和径流动能理论均能不同程度解释砒砂岩模拟边坡在不同冲刷流量、坡度和压实度下冲刷时侵蚀的产沙过程。5. EN-1掺量、养护龄期和压实度是影响砒砂岩人工固化边坡冲刷稳定性的主要因素。径流强度随压实度的增大而增大,EN-1掺量和养护龄期对其影响不显著。产沙强度和径流含沙量随养护龄期和压实度的增大而减小,黄绿色砒砂岩的产沙指标随EN-1掺量的增大先减小后增大,在0.2%达到最小值,灰黄色砒砂岩的产沙各指标随EN-1掺量的增大而减小。添加EN-1后,径流流速较素土有较大提高,随压实度的增大而增大,养护龄期对径流流速没有显著影响。在试验设计的EN-1掺量、养护龄期和压实度处理范围内,砒砂岩固化边坡冲刷时坡面径流均属于层流和急流。f随养护龄期和压实度的增大而减小,黄绿色砒砂岩的f随着EN-1掺量的增大先减小后增大,灰黄色砒砂岩的f随EN-1掺量的增大而减小, f与输沙率之间呈正相关关系。径流剪切力和径流功率理论可不同程度的解释砒砂岩固化边坡冲刷侵蚀的产沙过程。6.综合考虑EN-1对砒砂岩风化土抗剪强度、抗渗性能和抗冲刷性的影响,为提高砒砂岩地区边坡抵抗径流冲刷的能力,减轻水土流失的危害,在该地区EN-1固土护坡技术的工程实践中,建议最佳掺量为0.2%,养护龄期至少在15 d以上,压实度控制在95%以上,含水量控制在略低于最优含水量。更多还原

【Abstract】 Because of its unique geological features and climate characteristics, the Pisha sandstone region is called as“the maximum of soil and water loss”. Base on the objective of exploring slope erosion rules and reinforcement effect of EN-1 solidified agent to improve scour stability of slope in the region, combining the research methods of natural slope scouring test, laboratory soil engineering test and artificial simulation slope scouring test, taking the study on influencing factors of slope scour stability as the premise, analyzed the influence of EN-1 on engineering mechanical characteristics and simulated slope resistance to scour of Pisha sandstone weathered soil, elected the appropriate EN-1 content, curing age, compaction degree and soil water content of solidified slope in the region. Got the following progress:1. Current scour and slope gredient are the main factors that influence on scour stability of Pisha sandstone natural slope. Runoff intensity, sediment yield intensity and runoff sediment concentration increased with the increase of scour flow. Runoff intensity, sediment yield intensity and runoff sediment concentration of gray yellow Pisha sandstone first increased, then decreased with the increase of slope gredient, and the critical slope was 25°. Runoff producing and sediment yield indexes of gray white and red brown Pisha sandstone increased with the increase of slope gredient. Flow velocity increased with the increase of scour flow and slope gredient. The movement patterns of slope runoff were laminar flow under the scour flows and slope gredients in this experiment. The flow regimes were subcritical flow when scour flows and slope gredients were smaller, conversely, were supercritical flow. Runoff drag coefficient(f) of grey yellow and red brown Pisha sandstone decreased with the increase of scour flow, f of grey white Pisha sandstone increased with the increase of Scour flow. f of grey yellow Pisha sandstone presented the tendency that first increase, then decrease with the increase of slop gradient, f of grey white and red brown Pisha sandstone increased with the increase of slop gradient. Runoff shear stress, runoff power and runoff kinetic energy theory could explain the runoff sediment process of Pisha sandstone natural slope to varying degrees. Runoff drag coefficient, hydraulic radius, runoff power and runoff kinetic energy had bigger contribution to sediment yield of Pisha sandstone natural slope. 2. Vegetation coverage could obviously increase scour stability of Pisha sandstone natural slope. The size order of runoff intensity of Pisha sandstone natural slope were as follows: bare land>Chinese pine>grass land>korshinsk peashrub>seabuckthon. The size order of sediment yield intensity and runoff sediment concentration were as follows: bare land>grass land>korshinsk peashrub>Chinese pine>seabuckthon. Relative to grass land, korshinsk peashrub and Chinese pine, runoff and sediment reduction effect of Pisha sandstone natural slope of seabuckthorn coverage were biggest.3. EN-1 content, curing age, compaction degree and soil water content are the main factors that affect the characteristics of compaction, shear strength and impermeability of solidified soil. EN-1 had less influence on soil optimum moisture content of Pisha sandstone weathered soil, but could effectively improve the maximum dry density. The shear strength and impermeability of Pisha sandstone plain and solidified soil increased with the increase of compaction degree, the shear strength decreased with the increase of water content. The shear strength and impermeability improved significantly with the increase of EN-1 content and curing age.4. Current scour, slope gredient and compaction degree are the main factors that influence on scour stability of Pisha sandstone simulated slope. Runoff intensity increased with the increase of scour flow and compaction degree, slope gredient had no significant effect on runoff intensity. Sediment yield intensity and runoff sediment concentration increased with the increase of Scour flow, decreased with the increase of compaction degree, first increased, then decreased with the increase of slope gredient, the critical slope of yellow green and grey yellow Pisha sandstone were 60°and 50°. Flow velocity increased with the increase of scour flow, slope gradient and compaction degree. The movement patterns of slope runoff were turbulent flow when scouring proceeded to the later period at bigger scour flows and smaller compaction degrees. The movement patterns of slope runoff were all laminar flow at other treatments. The flow regimes were subcritical flow when scouring proceeded to the later period at smaller compaction degrees. The flow regimes were all supercritical flow at other treatments. f increased with the increase of Scour flow, decreased with the increase of compaction degree. f of Yellow green Pisha sandstone had tendency that first increase, then decrease with the increase of the slope gredient, and f of gray yellow Pisha sandstone had just the opposite trends with the slope gredient. Runoff shear stress, runoff power and runoff kinetic energy theory could explain the runoff sediment process of Pisha sandstone simulated slope at different scour fiow, slope gredient and compaction degree to varying degrees. 5. EN-1 content, curing age and compaction degree are the main factors that influence on scour stability of Pisha sandstone solidified slope. Runoff intensity increased with the increase of compaction degree, EN-1 content and curing age had no significant effect on Runoff intensity. Sediment yield intensity and runoff sediment concentration decreased with the increase of curing age and compaction degree, sediment yield indexes of yellow green Pisha sandstone first decreased, then increased with the increase of EN-1 content, and got minimum at 0.2% EN-1 content; sediment yield indexes of grey yellow Pisha sandstone decreased with the increase of EN-1 content. Flow velocity increased after adding EN-1, increased with the increase of compaction degree. Curing age had no significant effect on flow velocity. The flow regimes of Pisha sandstone solidified slop were all laminar flow and supercritical flow under the EN-1 content, curing age and compaction degree in this experiment. f decreased with the increase of curing age and compaction degree. f of yellow green Pisha sandstone first decrease, then increase with the increase of EN-1 content, f of grey yellow Pisha sandstone first increase, then decrease with the increase of EN-1 content. f had a positive correlation with sediment discharge rate. Runoff shear stress and runoff power theory could explain the erosion sediment yield process of Pisha sandstone solidified slope to varying degrees.6. Comprehensive consideration on EN-1 affection on shear strength, impermeability and scourresistance of Pisha sandstone weathered soil, in order to improve the ability of soil resistance runoff scour of slope in Pisha sandstone region, reduce the harm of soil and water losses in the region. Suggest optimum EN-1 content is 0.2%, curing age is at least 15 d above, controlling compaction degree above 95%, water content slightly less than optimum moisture content at project practice of EN-1 solidifying and protecting slope technology in the region.更多还原