本文選題：孔隙特征 + 反濾準(zhǔn)則��； 參考：《西北農(nóng)林科技大學(xué)》2017年碩士論文

【摘要】：世界大壩破壞實(shí)例調(diào)查結(jié)果表明,由滲透破壞而造成的大壩失事,占所有事故的40%以上。因此,土體的滲透破壞對(duì)土石壩安全影響程度很大。反濾層的使用既能保證防滲體的滲透穩(wěn)定,又可充分保證排水體的排水效果,從而顯著提高土石壩的安全度,由此可見對(duì)反濾層研究的重要性�，F(xiàn)有的反濾層設(shè)計(jì)主要是從顆粒粒徑的角度出發(fā)進(jìn)行研究,而實(shí)際上對(duì)于被保護(hù)土是顆粒問題,對(duì)反濾層應(yīng)該是孔隙的問題,也就是反濾層設(shè)計(jì)應(yīng)該從被保護(hù)土的顆粒特性與反濾層的孔隙特征的對(duì)比來考察,才能真正地反映反濾保護(hù)的特征。本文以橫泉水庫壩體黃土為研究對(duì)象,開展了系列抗?jié)B試驗(yàn)、激光粒度分析試驗(yàn)、壓汞試驗(yàn),并進(jìn)行了離散元軟件模擬,取得了以下幾方面結(jié)論:(1)反濾層有效孔隙直徑越小,被保護(hù)土的干密度越大,抗?jié)B臨界坡降就越大;將被保護(hù)黃土的抗?jié)B強(qiáng)度作為因變量,反濾層有效孔隙直徑、被保護(hù)土干密度作為自變量利用最小二乘法進(jìn)行多元回歸分析求得了兩個(gè)主要影響因素的權(quán)重,為反濾層的重要性提供可靠的數(shù)據(jù)支撐。(2)現(xiàn)有反濾層設(shè)計(jì)中安全系數(shù)有較大的優(yōu)化空間和提升潛力,在符合規(guī)范濾土排水要求的前提下,利用提出的臨界坡降公式可作為預(yù)估抗?jié)B臨界水力坡降的一種手段,有效降低安全系數(shù)的取值,節(jié)省投資。(3)易流失土顆粒主要集中在小顆粒,皆位于小于被保護(hù)土顆粒級(jí)配的d50的顆粒范圍內(nèi);反濾層鋼珠直徑越小,易流失土顆粒集中程度就越高。(4)激光法和比重計(jì)法具有良好的相關(guān)性,利用激光粒度分析儀代替?zhèn)鹘y(tǒng)的比重計(jì)具有可行性,而且激光法具有測(cè)量粒徑范圍廣、重現(xiàn)性好、測(cè)量速度快以及操作簡(jiǎn)單的優(yōu)點(diǎn),為反濾抗?jié)B試驗(yàn)流失土的測(cè)量提供了極大的便利,目前利用激光粒度儀測(cè)反濾抗?jié)B試驗(yàn)流失土顆粒級(jí)配曲線的做法較少。(5)壓汞試驗(yàn)主要用于測(cè)量塊體內(nèi)部或粉末表面的孔隙分布特性,對(duì)于測(cè)量散粒體的孔隙分布特性,目前方法還不成熟,有待進(jìn)一步完善。(6)針對(duì)符合碾壓式土石壩設(shè)計(jì)規(guī)范(SL274-2001)要求的反濾層采用離散元軟件進(jìn)行二維反濾層模擬,并加以CAD繪制孔隙,得到反濾層孔隙尺寸分布曲線。將該曲線上的孔隙直徑與插值法得到的有效孔隙直徑進(jìn)行對(duì)比,得到有效孔隙直徑為D_(孔20)。(7)在符合現(xiàn)有規(guī)范的前提下得到了小于0.075mm顆粒含量大于85%的粘性土基于孔隙特征的反濾層設(shè)計(jì)準(zhǔn)則。該準(zhǔn)則是在遵守規(guī)范的前提下對(duì)現(xiàn)有規(guī)范的補(bǔ)充,真正地反映反濾保護(hù)的本質(zhì),直觀的了解反濾層孔隙與被保護(hù)土顆粒應(yīng)滿足的關(guān)系,可有效服務(wù)于工程。
[Abstract]:The results show that the dam failure caused by seepage damage accounts for more than 40% of all accidents. Therefore, the seepage failure of soil has great influence on the safety of earth-rock dam. The use of filter layer can not only ensure the seepage stability of seepage control body, but also fully guarantee the drainage effect of drainage body, thus significantly improve the safety degree of earth-rock dam, so the importance of research on filter layer can be seen. The existing design of filter layer is mainly from the angle of particle size, but in fact, for the protected soil is a particle problem, the filter layer should be a pore problem. In other words, the design of filter layer should be examined from the comparison between the particle characteristics of the protected soil and the pore characteristics of the filter layer, in order to truly reflect the characteristics of the filter protection. In this paper, the loess of the dam body of Hengquan Reservoir is taken as the research object, a series of impermeability tests, laser particle size analysis tests, mercury injection tests are carried out, and the discrete element software simulation is carried out. The following conclusions are obtained: (1) the smaller the effective pore diameter of the filter layer, the smaller the effective pore diameter. The higher the dry density of protected soil is, the greater the critical slope of impermeability is, and the effective pore diameter of filter layer is determined by taking the impermeability strength of protected loess as dependent variable, The dry density of protected soil is used as independent variable and the weight of two main influencing factors is obtained by using least square method in multivariate regression analysis. Provide reliable data support for the importance of filter layer. (2) in the design of filter layer, the safety factor has great optimization space and lifting potential. The proposed formula can be used as a means to predict the critical hydraulic gradient of impermeable soil, which can effectively reduce the value of safety factor and save investment. (3) the particles of easily runaway soil are mainly concentrated in small particles. The smaller the diameter of the steel beads in the filter layer, the higher the concentration of the particles in the easily lost soil. (4) there is a good correlation between the laser method and the hydrometer method. It is feasible to use laser particle size analyzer instead of traditional hydrometer, and laser method has the advantages of wide range of particle size measurement, good reproducibility, fast measurement speed and simple operation. It provides great convenience for the measurement of soil loss in filtration and impermeability test. At present, there are few methods to measure particle gradation curve of lost soil by using laser particle size meter. (5) Mercury injection test is mainly used to measure pore distribution characteristics of bulk or powder surface, and to measure pore distribution characteristics of granular body. At present, the method is not mature and needs to be further improved. (6) according to the design code of roller compacted earth-rock dam (SL274-2001), the filter layer is simulated by discrete element software, and the pore is drawn by CAD. The pore size distribution curve of filter layer is obtained. The pore diameter on the curve is compared with the effective pore diameter obtained by interpolation method. The effective pore diameter of D _ (pore 20). (_ 7) is obtained and the design criteria of filter layer based on pore characteristics of cohesive soil with less than 85% 0.075mm particle content are obtained on the premise that the effective pore diameter is D _ (20). (_ 7) in accordance with the existing specifications. The criterion is a supplement to the existing code under the premise of complying with the code, which truly reflects the essence of filter protection, and intuitively understands the relationship between the pore of filter layer and the particle of protected soil, which can effectively serve the project.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TV640.33

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