本文選題：膨脹土 + 填方邊坡��； 參考：《西北大學(xué)》2013年博士論文

【摘要】：本文主要以安康地區(qū)的膨脹土填方邊坡為研究對象,以氣候的干濕循環(huán)(降雨-蒸發(fā))對其穩(wěn)定性及變形破壞的循環(huán)作用機理為研究目的,通過現(xiàn)場工程地質(zhì)調(diào)查、室內(nèi)物理力學(xué)特性試驗、現(xiàn)場物理模型試驗、現(xiàn)場記錄裂隙的定量描述以及熱濕耦合數(shù)值分析等多種手段,全面開展膨脹土填方邊坡在降雨-蒸發(fā)循環(huán)作用下各物理量的動態(tài)響應(yīng)規(guī)律及邊坡穩(wěn)定性研究；并分別對脹縮機理、降雨以及蒸發(fā)對膨脹土的作用機理和膨脹土邊坡的變形破壞機理進行探討。主要研究內(nèi)容及成果如下： (1)通過對安康地區(qū)膨脹土的工程地質(zhì)調(diào)查與室內(nèi)試驗,分析了膨脹土的物質(zhì)成分、結(jié)構(gòu)特征與基本物理性質(zhì)；在此基礎(chǔ)上,探討了不同飽和度下?lián)魧崢拥膲嚎s變形性能,并分別對不同初始狀態(tài)以及干濕循環(huán)作用影響下的強度特性進行了研究。結(jié)果表明：膨脹土的壓縮變形性能與飽和度呈負(fù)相關(guān)關(guān)系；不同初始狀態(tài)擊實樣的粘聚力差異極為明顯；隨著循環(huán)次數(shù)的增加,膨脹土的抗剪強度具有衰減性,且呈現(xiàn)先慢后快、最終趨于穩(wěn)定的趨勢。 (2)在安康膨脹土地區(qū)建立現(xiàn)場物理模型系統(tǒng),通過氣象觀測、土體溫濕度、土壓力、吸力及邊坡變形的監(jiān)測,采用自行組裝的數(shù)據(jù)采集系統(tǒng)與位移傳感器,研究了膨脹土填方邊坡在降雨-蒸發(fā)作用下各物理量的動態(tài)演化規(guī)律及其影響因子。結(jié)果表明：邊坡的工程性狀與含水量的變化息息相關(guān)；其中,降雨是影響膨脹土含水量最直接的因素,而蒸發(fā)作用屬于間接影響因素,二者的耦合作用使邊坡趨于變形破壞。 (3)在明確填方邊坡的裂隙類型為風(fēng)化裂隙的基礎(chǔ)上,利用矢量圖技術(shù)定量化描述了裂隙的演化規(guī)律,獲取了裂隙的幾何形態(tài)及裂隙度等一系列參數(shù)；進而分別探討了干濕循環(huán)、含水量及大氣溫度等因素對裂隙發(fā)育的影響。結(jié)果表明：監(jiān)測期內(nèi)裂隙分布不具備定向規(guī)律,而且系統(tǒng)格局非常混亂,基本不存在相互平行的裂隙；裂隙在降雨時閉合,在蒸發(fā)過程中再次開裂,并互相連通逐漸發(fā)育成網(wǎng)狀,但到一定程度后基本穩(wěn)定；隨著循環(huán)次數(shù)的增加,土體逐步走向完全破碎。 (4)在前人研究成果的基礎(chǔ)上,提出降雨-蒸發(fā)作用下膨脹土的脹縮機理：降雨時,水分子進入土體并不斷包裹晶層、土顆粒及其集聚體,并通過復(fù)雜的物理化學(xué)作用轉(zhuǎn)化為力學(xué)作用與其相互聯(lián)結(jié),形成結(jié)合水膜,由于結(jié)合水膜的增厚,晶層、粒間距離加大,導(dǎo)致土體產(chǎn)生膨脹；反之,水膜變薄或消失時,粒間距離減小,從而使土體體積縮小。 (5)在對降雨及蒸發(fā)的物理過程有清晰了解的基礎(chǔ)上,首先通過室內(nèi)試驗、現(xiàn)場模型試驗結(jié)果的分析,提出膨脹土水土物理力學(xué)作用機理；并結(jié)合水土化學(xué)作用類型及膨脹土主要礦物成分的探討,提出膨脹土水土化學(xué)作用機理。其次,對降雨作用的沖刷侵蝕,以及蒸發(fā)作用的土體收縮開裂的力學(xué)機制進行深入研究,推導(dǎo)了土顆粒沖刷啟動條件、坡面宏觀徑流沖刷及土體開裂等一系列力學(xué)公式。最終,綜合以上幾個方面,對降雨-蒸發(fā)循環(huán)作用下膨脹土填方邊坡的變形破壞機理做出了全面的解釋。得出：蒸發(fā)是邊坡變形破壞的重要前提條件,而降雨是導(dǎo)致變形破壞的直接原因；二者的循環(huán)作用可導(dǎo)致膨脹土填方邊坡產(chǎn)生破壞。 (6)詳細(xì)介紹了熱濕耦合的理論模型、邊界條件以及計算參數(shù)的賦值情況,并以現(xiàn)場試驗邊坡為原型建立幾何模型,對其進行數(shù)值對比分析,驗證了所用理論模型、邊界條件的正確性。在此基礎(chǔ)上,對考慮裂隙的邊坡熱濕耦合性狀進行分析,結(jié)果表明：裂隙的存在使邊坡對降雨-蒸發(fā)效應(yīng)的響應(yīng)顯著,不但為雨水入滲至邊坡內(nèi)部提供了快速通道,使土體的滲透性能得到極大提高,而且在蒸發(fā)過程中,裂隙面與大氣直接接觸,同樣也為水分的遷出提供了便捷。 (7)針對數(shù)值分析時需同時兼顧降雨及蒸發(fā)兩種作用類型的特點,采用將裂隙的兩側(cè)視為氣候作用邊界的方法,使降雨-蒸發(fā)作用下邊坡內(nèi)部的水分變遷可通過裂隙與外界建立聯(lián)系,并仍認(rèn)為裂隙分割而成的土塊完全符合非飽和土滲透特性。這種方法既考慮了裂隙對降雨-蒸發(fā)的影響,又符合非飽和土力學(xué)理論,適用于裂隙膨脹土填方邊坡的數(shù)值分析。 (8)在以上研究和數(shù)值分析成果的基礎(chǔ)上,對考慮裂隙以及強度衰減的邊坡穩(wěn)定性進行了分析。結(jié)果表明：只考慮裂隙的邊坡潛在滑裂面與降雨作用下濕度場的分布密切相關(guān),滑裂面隨降雨作用逐漸趨于在淺層發(fā)生,但總體安全系數(shù)較高�？紤]強度衰減后,安全系數(shù)要遠(yuǎn)小于未考慮強度衰減的,且隨著干濕循環(huán)次數(shù)的增加而不斷降低,最終趨于失穩(wěn)。同時將膨脹土的裂隙性及強度衰減特性計入邊坡穩(wěn)定性分析中,所得計算結(jié)果符合人們的認(rèn)知,可真實反映邊坡的破壞情況。
[Abstract]:This paper mainly takes the expansive soil slope in Ankang area as the research object, and uses the dry and wet cycle of the climate (rainfall evaporation) to study the circulation mechanism of its stability and deformation damage, and through the field engineering geological survey, the indoor physical and mechanical properties test, the field physical model test, the quantitative description of the field record of the cracks and the quantitative description of the cracks. The dynamic response of various physical quantities of expansive soil slope under the action of rainfall evaporation cycle and the stability of slope under the effect of rainfall evaporation cycle are carried out comprehensively. The mechanism of expansion and shrinkage, the mechanism of rainfall and evaporation on expansive soil and the deformation and failure mechanism of expansive soil slope are discussed. The contents and results are as follows:
(1) through the engineering geological investigation and laboratory test of expansive soil in Ankang area, the material composition, structural characteristics and basic physical properties of expansive soil are analyzed. On this basis, the compressive deformation properties of the compaction samples under different saturation are discussed, and the strength characteristics under the influence of different initial state and dry and wet circulation are carried out respectively. The results show that the compressive deformation performance of expansive soil has a negative correlation with saturation, and the cohesiveness difference between different initial states is very obvious. With the increase of the cycle times, the shear strength of expansive soil is attenuated, and it is slow and fast, and eventually tends to stability.
(2) a field physical model system was established in the Ankang expansive land area. Through the monitoring of temperature and humidity, soil pressure, suction and slope deformation, the dynamic evolution law and influencing factors of the physical quantities of the expansive soil slope under the action of rainfall evaporation were studied by the meteorological observation, soil temperature and humidity, soil pressure, suction and slope deformation. The results show that the engineering properties of the slope are closely related to the change of water content, in which the rainfall is the most direct factor affecting the water content of the expansive soil, and the evaporation is an indirect influence factor. The coupling effect of the two causes the slope to be deformed and destroyed.
(3) on the basis of the crack type of the fill slope, the vectorgraph technique is used to quantitatively describe the evolution law of the fissure, obtain a series of parameters such as the geometric shape and crack degree of the fissure, and then discuss the effects of dry and wet cycle, water content and atmospheric temperature on the fracture development. In the monitoring period, the distribution of the cracks does not have the orientation law, and the system pattern is very chaotic, and there is no parallel cracks. The cracks are closed in the rainfall and are cracked again during the evaporation process, and they are connected gradually into a network, but it is basically stable after a certain degree. With the increase of the cycle times, the soil gradually goes to complete. Fracture.
(4) on the basis of previous research results, the expansion and contraction mechanism of expansive soil under rainfall evaporation is proposed. When rainfall, water molecules enter the soil and continuously wrap the crystal layer, soil particles and their clusters, and interconnect with the mechanical action through complex physical and chemical effects, forming a combined water film, because of the thickening of the water film and the crystal layer. As the distance between grains increases, the soil expands; otherwise, when the water film thins or disappears, the distance between grains decreases, thus reducing the volume of the soil.
(5) on the basis of the clear understanding of the physical process of rainfall and evaporation, first through the laboratory test and the analysis of the results of the field model test, we put forward the mechanism of soil and water physical and soil mechanics of expansive soil, and put forward the mechanism of soil and water chemical action of expansive soil combined with the types of soil and water chemical action and the main mineral composition of expansive soil. Secondly, the mechanism of soil and water chemical action of expansive soil is put forward. The erosion erosion of rainfall and the mechanical mechanism of soil shrinkage cracking caused by evaporation are deeply studied. A series of mechanics formulas are derived, such as the starting condition of the soil particle scour, the macroscopic runoff scour of the slope and the soil cracking. Finally, the deformation of the expansive soil fill slope under the action of rainfall evaporation cycle is broken. A comprehensive explanation of the bad mechanism is made. It is concluded that evaporation is an important prerequisite for the deformation and failure of the slope, and the rainfall is the direct cause of the deformation and failure, and the cyclic action of the two can cause the failure of the expansive soil fill slope.
(6) the theoretical model of heat and humidity coupling, the boundary condition and the calculation of the calculation parameters are introduced in detail, and the geometric model is built on the site test slope as the prototype. The numerical comparison and analysis are carried out to verify the theoretical model and the correctness of the boundary conditions. On this basis, the thermal and wet coupling properties of the slope are analyzed. The results show that the existence of the crack leads to the significant response of the slope to the rainfall evaporation effect, which not only provides a fast channel for the infiltration of rainwater into the slope, but also greatly improves the permeability of the soil. In the process of evaporation, the fracture surface is directly exposed to the atmosphere, and it also provides convenience for the migration of water.
(7) according to the characteristics of the two types of action of rainfall and evaporation at the same time, the two sides of the fracture are considered as the boundary of the climatic action, so that the water change in the slope inside the slope can be connected to the outside by the fissure, and the soil block divided by the split gap is still fully conformed to the infiltration of the unsaturated soil. The method not only takes account of the influence of cracks on rainfall evaporation, but also accords with the theory of unsaturated soil mechanics, and is suitable for numerical analysis of the expansive soil fill slope.
(8) on the basis of the above and numerical analysis results, the slope stability considering the crack and the intensity attenuation is analyzed. The results show that the potential sliding surface with only the crack is closely related to the distribution of the humidity field under the rainfall action, and the sliding surface tends to occur in the shallow layer with the rainfall, but the overall safety coefficient is more than that. When the strength attenuation is considered, the safety factor is far less than that of unconsidered strength attenuation, and it decreases with the increase of dry and wet cycles, and eventually tends to instability. At the same time, the fracture and strength attenuation characteristics of expansive soil are included in the slope stability analysis. The calculated results conform to people's cognition, which can truly reflect the failure of the slope. Situation.

【學(xué)位授予單位】：西北大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：TU443;TU43

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