本文關鍵詞： 凍土路基 隨機有限元 局部平均法 隨機溫度場 本構模型 隨機應力場 隨機變形場　出處：《中國礦業(yè)大學》2015年博士論文　論文類型：學位論文

【摘要】：多年凍土區(qū)公路及鐵道工程路基熱-力穩(wěn)定性問題是一個亟待解決的工程難題,國內外學者對其進行了大量的研究,但考慮參數(shù)隨機性的研究較少。與一般巖土工程中存在諸多不確定性因素類似,對于凍土工程,由于冰的存在,其工程性質復雜而特殊,表現(xiàn)出很強的離散性和隨機性。為此,本文以多年凍土地區(qū)路基為研究對象,考慮凍土熱力學參數(shù)的隨機特性,采用理論分析與數(shù)值計算相結合的方式,建立典型路基隨機溫度場、隨機變形場及隨機應力場分析模型,為青藏高原多年凍土路基工程長期穩(wěn)定性及可靠性評價提供依據(jù)。首先,引進隨機場及其局部平均理論對凍土土性參數(shù)進行隨機場描述與離散,提出實用性更廣的三角形單元局部平均法。研究結果表明:隨機場描述方法能合理考慮土性參數(shù)空間上的變異性;土性參數(shù)模擬為隨機場和隨機變量獲得的均值結果相同,模擬為隨機變量獲得的變異性偏高;傳統(tǒng)四邊形單元局部平均法中,被包含的兩個三角形單元數(shù)字特征不一定相同,且不等于包含的四邊形隨機場單元的數(shù)字特征,將其應用于三角形單元有限元法存在偏差;三角形單元局部平均法能與三角形單元有限元法完美結合,隨機場單元與有限元單元對應關系清晰,操作方便,易于編程。其次,將多年凍土地區(qū)路基上邊界條件模擬為隨機過程,凍土熱學參數(shù)模擬為隨機場,基于三角形單元局部平均法及NSFEM方法,自行研制開發(fā)了多年凍土地區(qū)路基溫度場隨機有限元程序,計算獲得了溫度均值及溫度標準差。研究結果表明:考慮參數(shù)隨機性得到的溫度場均值結果與傳統(tǒng)確定性溫度場結果相同;參數(shù)變異系數(shù)相同時,不同時刻較高的溫度標準差位置不同,參數(shù)變異系數(shù)不同時,變異系數(shù)越大,溫度變異性越強;地基中存在大量的高溫凍土,由于區(qū)域內標準差的存在,高溫凍土的熱力學狀態(tài)存在隨機性;考慮氣候變暖條件下,溫度標準差總體隨時間呈增加趨勢。再次,基于修正劍橋模型及雙屈服面理論,考慮凍土黏聚力及內摩擦角的影響,以整體變形特性εv-lnp曲線對試樣的變形進行描述,采用應力路徑相關因子對等向固結路徑獲得的屈服面硬化參數(shù)進行了修正,結合凍土臨界狀態(tài)參數(shù)得到了能夠體現(xiàn)凍土固有臨界特性的參考屈服面硬化參數(shù),并由當前屈服面與參考屈服面間的關系定義了能夠反映凍土當前狀態(tài)的固結參數(shù)及潛在強度,得到了能夠有效反應凍土剪縮、剪脹、硬化和軟化特性的凍土模型。根據(jù)經(jīng)典的彈塑性理論,推導了所得模型增量形式的應力-應變關系,結合變剛度彈塑性有限元算法,詳細討論了在有限元計算中開發(fā)模型計算程序的數(shù)值實現(xiàn)過程。最后,考慮隨機溫度對凍土區(qū)土體基本力學參數(shù)的強烈決定作用,將凍土力學參數(shù)模擬為隨機場,基于三角形單元局部平均法及NSFEM方法,自行研制開發(fā)了多年凍土地區(qū)路基應力場與變形場隨機有限元程序,計算獲得了位移場與應力場的統(tǒng)計特征及其動態(tài)發(fā)展過程。研究結果表明:溫度變化主要影響豎向位移均值及豎向位移標準差分布;路基斷面特定位置沉降均值變化可分為沉降、凍脹、再沉降三個階段,且距離路堤上表面越近,分段現(xiàn)象越明顯;參數(shù)變異系數(shù)不同時,變異系數(shù)越大,位移標準差與應力標準差均越大,變異性越強;考慮氣候變暖條件下,路基斷面特定位置沉降標準差總體隨時間呈增加趨勢。
[Abstract]:Permafrost area of highway and railway subgrade thermal stability problem is an urgent need to solve the engineering problems, the domestic and foreign scholars have done a lot of research on it, but considering randomness less. And there are many uncertainties in general in geotechnical engineering for frozen soil engineering, due to the presence of ice. The engineering properties of complex and special, exhibit discrete and strong randomness. Therefore, based on the roadbed in the permafrost area as the research object, considering the random characteristics of thermodynamics parameters of frozen soil, using theoretical analysis and numerical calculation of the combined mode, set up a random temperature field of roadbed deformation, random field and stochastic stress field the analysis model for the long-term stability of permafrost subgrade engineering and provide the basis for the reliability evaluation. Firstly, with the introduction of the airport and the local average theory of frozen soil parameters with The airport is described and discrete, proposed triangular element local average method is wider in practicability. The research result shows that the method can describe the airport with reasonable consideration of variability of the soil parameter space; simulation of soil parameters as the mean random field and random variables obtained the same result, simulation of high variability for local random variables; the average traditional method of quadrilateral element, two triangular element digital features included are not necessarily the same, and is not equal to the quadrilateral with digital features include airport unit, applied to the triangular finite element method in deviation; local average method of triangular elements can be combined with triangular finite element method with perfect. The corresponding airport unit and finite element relationship clear, convenient operation, easy programming. Secondly, the boundary conditions of the permafrost subgrade simulated as stochastic process, soil thermal parameters model To be with the airport, the triangular element local average method and the NSFEM method was developed based on stochastic finite element program of temperature field of Subgrade in permafrost region, calculate the mean temperature and temperature standard deviation. The results show that: considering the mean temperature field results of random parameters obtained with the traditional deterministic temperature field results in the same parameter variation; at the same temperature coefficient, high standard of different time difference in different positions, the coefficient of variation is not at the same time, the coefficient of variation is larger, the temperature variability is strong; there are a lot of foundation in high temperature permafrost region, due to the existence of standard deviation, the thermodynamic state of permafrost are random; considered under the condition of climate warming, temperature standard the overall difference increased with the increase of time. Once again, the modified Cambridge model and double yield surface based on the theory, considering the soil cohesion and internal friction angle of the impact to the overall change The deformation of shape characteristic curve of specimen epsilon v-lnp described by stress path correlation factor to obtain equivalent consolidation path yield surface hardening parameter is modified, combined with the critical state parameters of frozen soil obtained can reflect the inherent characteristics of frozen soil critical reference yield surface hardening parameters, and the current yield surface and the relationship between the yield of reference the definition can reflect the current state of frozen soil consolidation parameters and potential strength, the frozen soil can reflect the effect of shear contraction dilatancy, hardening and softening characteristics of the frozen soil model. According to the classical elastic-plastic theory, deduced the model incremental stress-strain relationship with variable stiffness elastic plastic finite element the realization process of numerical algorithm, calculation program development model in finite element analysis are discussed in detail. Finally, considering the strong random temperature on the basic mechanical parameters of soil for permafrost area With the simulation of frozen soil mechanics parameters for random and triangular element local average method and the NSFEM method was developed based on the permafrost subgrade stress field and deformation field of stochastic finite element program, the displacement field calculation development and statistical characteristics of stress field and dynamic process. The results show that the effect of temperature the change of vertical displacement and vertical displacement of the mean standard deviation distribution; specific location of subgrade section settlement changes can be divided into settlement, frost, and settlement of three stages, and the distance between the upper surface of the embankment near the segmentation phenomenon is more obvious; the coefficient of variation is not at the same time, the coefficient of variation is larger, the standard deviation of displacement and stress standard deviation all the greater variability is considered strong; under the condition of climate warming, specific location of subgrade section settlement overall standard deviation over time showed an increasing trend.

【學位授予單位】：中國礦業(yè)大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：U213.1;U416.1
，

本文編號：1549708