本文選題：侵蝕過程 + 土石比�。� 參考：《西南大學》2015年碩士論文

【摘要】：隨著生產建設項目數量不斷增加和類型多樣化,各種工程建設活動在施工過程中形成了大量的工程堆積體,使原地貌單元不斷被塑造成特殊的人為地貌單元。工程堆積體作為一種物質組成極不均勻、離散程度很大的土石混合物,其結構松散、內摩擦角和粘聚力小、植物根系與有機質缺乏,是人為水土流失的主要地貌單元。在降雨或暴雨條件下,其強烈的水土流失破壞了土地資源和生態(tài)平衡。由于工程堆積體發(fā)生來源和土石含量不同,不同工程堆積體在地表徑流沖刷作用下的土壤侵蝕特征差異性較大。本文以重慶市生產建設中廣泛存在的紫色土堆積體和黃壤堆積體為研究對象,通過野外調查及土工試驗方法,分析了其來源特征及物理性質變化特征；采用野外實地放水沖刷法及水力學、泥沙運動力學等理論,深入研究了不同土石比工程堆積體邊坡坡面徑流侵蝕過程中水動力學參數變化特征、坡面入滲、產流、產沙過程及細溝發(fā)育過程,建立了邊坡坡面水沙關系方程及侵蝕臨界條件；通過研究不同土石比工程堆積體物理性質、水動力學參數、徑流泥沙及細溝發(fā)育特征,深入分析工程堆積體邊坡坡面土壤侵蝕過程,并進一步探討其邊坡失穩(wěn)機制,可為生產建設項目水土流失量預測和水土保持措施布置提供基本參數和技術依據。主要結論如下：(1)不同土石比工程堆積體邊坡物理性質特性差異明顯。土質(≤10mm)含量較高時,土體容重、非毛管孔隙均較小,而毛管孔隙較大,有利于邊坡植物恢復,但其豐富土質或細顆粒是徑流侵蝕的泥沙來源；而石質(10mm)較高時則相反,其水土流失發(fā)生的可能性較小。紫色土和黃壤堆積體土質含量均表現為土質偏土質土石混合質,其中紫色土依次為86.47%,79.19%和57.16%,黃壤依次為76.88%和60.69%,而石質含量則相反,除土質紫色土外,其它堆積體顆粒分布均勻且級配良好；紫色土堆積體十體容重以土質(1.317g/cm3)最小,土石混合質最大(1.562g/cm3),而黃壤堆積體為偏土質大于土石混合質；兩種堆積體體邊坡沖刷前的初始含水率均表現為土質偏土質土石混合質,土質含量多的堆積體較含量少的侵蝕危險性越高。工程建設形成的各種擾動地貌單元降低了項目區(qū)水源涵養(yǎng)功能,其中3a,2a和1a棄渣堆積體土壤有效庫容比原地貌中最小的坡耕地依次減少了12.3%,16.8%,22.7%。(2)不同土石比工程堆積體邊坡坡面徑流侵蝕過程中水動力學參數變化明顯。在邊坡坡面侵蝕過程中水流流態(tài)以紊流和緩流為主,且各水動力學參數均呈不同程度波動式變化,其中流速v隨沖刷時間呈“強-弱”波動、阻力系數f呈“弱-強”波動、剪切力τ呈“弱-強-弱”波動、功率P呈“強-弱”波動；紫色土和黃壤堆積體v均隨放水流量增加呈冪函數增加,其冪指數最大和最小值分別為0.526,0.179；同一放水流量下土質或偏土質堆積的v均為最大,含石量越小時坡度及坡長對v影響較小。在一定條件下/隨土石比的減小而增大,即土質偏土質土石混合質。τ受土石比和地形條件(坡度或坡長)影響很大,其隨放水流量增加而增大且黃壤堆積體增加速率較紫色土快,其中紫色土堆積體在24.571～83.743 Pa之間,而黃壤為22.000～57.154 Pa。P也隨放水流量增加而增大,兩種堆積體P均表現為土質或偏土質大于土石混合質。(3)不同土石比工程堆積體邊坡徑流泥沙特征差異明顯。入滲過程存在迅速降低(前3min)、緩慢降低(3-20min)和趨于穩(wěn)定(20min后)三個階段；紫色土和黃壤堆積體邊坡在沖刷過程中的平均入滲率均表現為土質或偏土質大于土石混合質。產流過程則呈先增加后趨于穩(wěn)定變化且存在不同程度突變或波動現象,產流率突變主要發(fā)生在產流后的9 min內；細溝侵蝕是影響產流量的重要因素；土石比對產流率有重要影響且隨放水流量增加而增強,流量從5增加到25 L/min土質堆積體平均產流率增加量最大(19.337 L/min),而土石混合質最小。產沙過程呈連續(xù)性的多峰多谷特點且波動程度隨放水流量增加而增強,細溝溝壁土體在重力作用下的崩塌脫落是造成產沙過程波動的重要原因。各水動力學參數對邊坡坡面產沙量影響程度依次為γ Qγhγbγ,fγvγpγτ,其關聯度在0.5183～0.9284之間,其中放水流量對產沙量影響最大；產沙量與放水流量可用M=0.0072Q 3.0287進行回歸擬合,小流量下(5L/min)兩種堆積體邊坡平均產沙率均以土石混合質最大,而在大流量下則表現為土質偏土質土石混合質。(4)工程堆積體邊坡坡面細溝侵蝕主要發(fā)生在產流3min后,可分為細溝發(fā)展階段(3～45min)和穩(wěn)定階段(45min后),其徑流含沙量呈波動減小的變化,而坡面細溝形態(tài)與產沙量密切相關。在徑流沖刷后黃壤堆積體一般形成單一主溝,而紫色土堆積體則形成較多細溝；土石混合質紫色土堆積體邊坡細溝條數、平均溝寬、平均溝深總體上隨放水流量增加而增大,而細溝寬深比則相反,坡度增大會加劇溝底下切；當放水流量在10～30 L/min范圍時其平均溝深在1.58～7.67 cm之間變化,而細溝平均密度在1.0～2.27m/m2。工程堆積體邊坡坡面產沙量與平均溝深呈極顯著正相關,其可用M=0.2187h2.9508進行回歸擬合,而與侵蝕溝條數、平均溝寬、細溝密度以及細溝寬深比相關性不明顯。(5)工程堆積體邊坡細溝發(fā)育過程中的重力侵蝕發(fā)生在細溝兩側及溝頭,是影響坡面產沙重要因素,也是導致坡面含沙量波動變化重要原因。邊坡細溝發(fā)育過程中的重力侵蝕產沙貢獻最大為96.6%,最小為10.9%,相同條件下重力侵蝕產沙貢獻隨邊坡坡度增加而增大。不同土石比邊坡坡面的侵蝕臨界條件不同,偏土質紫色土堆積體邊坡坡面發(fā)生侵蝕的臨界水流功率較小(6.699N/(m·s)),而其土石混合質較大(7.265N/(m·s))；土石比相同時,黃壤堆積體臨界水流功率小于紫色土堆積體,黃壤堆積體較紫色土堆積體易侵蝕；工程堆積體邊坡侵蝕臨界坡度隨放水流量增加而減小,放水流量由10增加到30 L/min時土石混合質紫色土堆積體侵蝕臨界坡度依次為35。,35。,30。,32.5。和30。。(6)工程堆積體邊坡的入滲產流過程對邊坡穩(wěn)定性影響很大,其徑流沖刷過程會直接造成坡面粗糙化、石礫化,而水分入滲過程則會增大土體含水率和土體容重,降低土體抗剪強度,造成邊坡失穩(wěn)。在非降雨條件和中雨(歷時18h且雨量為23.3mm)條件下,基于SLOPE/W模型的紫色土堆積體邊坡安全系數分別為2.863和1.600,非降雨條件下堆積體邊坡滑動面發(fā)生在母巖表面與底層土壤之間,而中雨條件下則發(fā)生在堆積體底部與表層土壤之間,表層土壤在水分的作用下容易發(fā)育成軟弱面或滑帶土。工程堆積體邊坡穩(wěn)定性受多因素的復合作用,主要包括邊坡土體工程特性、邊坡形態(tài)和地質地貌等內部因素和降雨、邊坡植被、外力作用、風化作用以及人類活動等外部因素。
[Abstract]:With the increasing number and variety of the production and construction projects, a large number of Engineering accumulation bodies have been formed during the construction process, and the original geomorphic units have been moulded into special man-made geomorphic units. Loose, internal friction angle and cohesive force and lack of plant root and organic matter are the main geomorphic units of artificial soil erosion. Under the conditions of rainfall or rainstorm, the strong soil erosion has destroyed the balance of land resources and ecological balance. The characteristics of soil erosion are different. In this paper, purple soil heap and yellow soil accumulation in Chongqing production and construction are studied. Through field investigation and geotextile test, the characteristics of the source and physical properties of the soil are analyzed. The characteristics of the variation of hydrodynamic parameters, the infiltration, runoff production, sediment production and rill development of the slope surface runoff erosion process of different soil and rock slope surface runoff are studied, and the relationship equation of water and sediment and the critical condition of the slope are established, and the physical properties of the different soil and stone than the engineering accumulation body are studied. Dynamic parameters, runoff and sediment and rill development characteristics, in-depth analysis of soil erosion process in the slope of Engineering accumulation slope, and further discuss the mechanism of slope instability, which can provide basic parameters and technical basis for the prediction of soil erosion and soil and water conservation measures in production and construction projects. The main conclusions are as follows: (1) different soil and rock ratio Engineering The physical properties of the pile slope are very different. When the content of soil (less than 10mm) is high, the bulk density of soil and the non capillary pores are small, but the pores of the capillary are large, which are beneficial to the restoration of the slope plants. But the rich soil or fine particles are the sediment sources of runoff erosion; while the high 10mm is the opposite, and the possibility of soil erosion is more likely. The soil content of purple soil and yellow soil accumulation body is all soil mass soil and stone mixture, purple soil is 86.47%, 79.19% and 57.16%, yellow soil is 76.88% and 60.69% in turn, and the content of stone is the opposite. Besides the purple soil, the other accumulation body particles are evenly distributed and the gradation is good, and the ten body bulk density of purple soil heap body is soil. The mass (1.317g/cm3) is the smallest, the soil and rock mixture is the largest (1.562g/cm3), but the yellow soil accumulation body is larger than the soil and rock mass, and the initial water cut before the two kinds of pile body slope scour is all soil mass soil and rock mixture, the less accumulation of soil content is more dangerous. The dynamic geomorphic unit reduced the water conservation function of the project area, in which the soil effective storage capacity of 3a, 2a and 1A residue deposits decreased by 12.3%, 16.8%, 22.7%. (2), and the variation of hydrodynamic parameters in the erosion process of slope surface runoff in the slope surface of the slope. The flow state is mainly turbulence and slow flow, and the hydrodynamic parameters are fluctuating in varying degrees. The flow velocity V fluctuates with the "strong weak" fluctuation with the scouring time, the resistance coefficient f is "weak strong" fluctuation, the shear force is "weak strong weak" fluctuation, the power P is "strong weak" wave, and the V of purple soil and yellow soil accumulation body increases with the discharge flow rate. The maximum power exponent and the minimum value of the power exponent are 0.526,0.179, and the V of the soil and the partial soil under the same discharge flow is the largest, the hourly slope and the length of the rock are less affected by the v. In certain conditions / with the decrease of the soil and rock ratio, the soil and rock mass mixture. Tau is subjected to the soil rock ratio and the topographic strip. The slope or slope length has great influence, which increases with the increase of discharge flow and the increase rate of the yellow soil accumulation body is faster than the purple soil, and the purple soil heap is between 24.571 and 83.743 Pa, and the yellow soil is 22 ~ 57.154 Pa.P with the increase of the discharge flow, and the two kinds of accumulation body P are all soil or more than the soil and rock mass. 3) the difference of runoff and sediment characteristics of different soil and rock slope is obvious. Infiltration process has a rapid decrease (former 3min), slow decrease (3-20min) and stabilization (after 20min), and the average infiltration rate of purple soil and yellow soil accumulation slope in the process of erosion is both soil and soil mass greater than soil and rock mixture. The process is increased first and then tends to be stable and varied, and there are different degrees of mutation or fluctuation. The mutation of the rate of production mainly occurs in the 9 min after the flow. The rill erosion is an important factor affecting the flow rate; the soil and stone has an important influence on the rate of production and increases with the increase of the discharge flow, and the flow rate increases from 5 to 25 L/min soil accumulation. The increase of average yield is the largest (19.337 L/min), but the soil and rock mixture is the smallest. The process of sediment yield is a continuous multi peak and multi Valley characteristic and the fluctuation degree increases with the increase of discharge flow. The collapse and fall off of the soil under the action of gravity is the main reason for the fluctuation of the sand production process. The degree of influence in turn is gamma Q gamma h gamma B gamma and f gamma V gamma P gamma ray. The correlation degree is between 0.5183 and 0.9284. The discharge flow rate has the greatest impact on the sediment yield, and the sediment yield and discharge flow can be fitted with M=0.0072Q 3.0287, and the average sediment yield of the two accumulation slopes under small flow (5L/min) is the largest in the soil and rock mass, and under the large flow rate. (4) the rill erosion of the slope surface of the slope of the engineering accumulation mainly occurs after the flow of 3min, which can be divided into the development stage of the rill (3 ~ 45min) and the stable stage (after 45min), and the sediment concentration in the runoff is fluctuating and decreasing, and the form of the rill in the slope is closely related to the sediment yield. In general, the body forms a single main trench, while the purple soil heap forms more rill; the number of slill strip in the slope of the soil and rock mixed purple soil heap is wide. The average furrow depth increases with the increase of the discharge flow, while the width depth ratio of the rill is the opposite, and the increase of the slope will aggravate the bottom cutting. When the discharge flow is in the range of 10~30 L/min, The average furrow depth varies between 1.58 and 7.67 cm, while the average density of the rill average density is very significant positive correlation with the average furrow depth in the slope surface of the engineering accumulation body from 1 to 2.27m/m2.. It can be regressed with M=0.2187h2.9508, but the correlation with the number of gully, the average groove width, the rill density and the width depth ratio of the rill are not obvious. (5) the construction of the project is not obvious. Gravity erosion occurred on both sides of the rill and the head of trench during the development of the rill of the slope. It is an important factor affecting the sediment yield in the slope. It is also an important cause of the fluctuation of the sediment content in the slope. The maximum contribution of gravity erosion to sediment yield is 96.6% and the minimum is 10.9%. The contribution of gravity erosion to sand production under the same condition is with the slope slope. The critical flow power of different soil and rock is different than that of slope slope, and the critical flow power of the slope surface erosion of the purple soil heap slope is smaller (6.699N/ (M. S)), and the soil and rock mixture is larger (7.265N/ (M. S)), and the critical flow power of the yellow soil accumulation body is less than the purple soil heap, Huang Rangdui. The critical slope of the slope erosion of the engineering accumulating body decreases with the increase of the discharge flow, and the critical slope of the soil and rock mixed purple soil heap erosion is 35., 35., 30., 32.5. and 30.. (6) Engineering heap slope influence on the slope stability in order to reduce the critical slope of the slope erosion of the slope of the engineering accumulation body. The critical slope of the slope erosion of the slope of the engineering accumulation body decreases with the increase of the discharge flow. The process of runoff scouring will directly cause slope roughness and gravel, and water infiltration will increase soil moisture content and soil bulk density, reduce soil shear strength and cause slope instability. Under the condition of non rainfall and rain (18h and rainfall of 23.3mm), the slope safety system based on SLOPE/W model is based on the model of purple soil. The numbers are 2.863 and 1.600 respectively. The sliding surface of the pile slope under non rainfall conditions occurs between the surface of the parent rock and the bottom soil, while the medium rain occurs between the bottom of the pile and the surface soil. The surface soil is easily developed into soft surface or slide soil under the action of water. The stability of the slope of the engineering accumulation body is complex by multiple factors. The effects mainly include the engineering characteristics of slope soil, the internal factors of slope shape, geological and geomorphology and other internal factors, such as rainfall, slope vegetation, external force, weathering and human activities.

【學位授予單位】：西南大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：S157

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