東非黑棉土的膨脹特性及處治技術(shù)研究
發(fā)布時間：2019-03-25 13:55
【摘要】：近年來,我國工程建設(shè)集團在東非國家承擔的公、鐵路建設(shè)項目中,經(jīng)常遇到當?shù)睾诿尥翈淼墓こ虇栴}。由于黑棉工具有較強的膨脹性,會使道路工程產(chǎn)生嚴重病害,因而不得不采用換填方案,增加了工程成本和土方量。對東非黑棉土的膨脹特性和處治技術(shù)進行深入研究,可以增加工程安全性、降低工程造價、提升環(huán)境效益。依托中資企業(yè)在東非地區(qū)的公、鐵路工程項目,對東非黑棉土的概念、危害、分布以及地形地貌特征和氣候特征等情況進行了詳細地調(diào)研,并借助工程勘察資料和土工現(xiàn)場試驗,對東非黑棉土的工程性質(zhì)進行了初步地分析。對東非黑棉土原狀土樣的基本工程性質(zhì)進行了試驗和分析。依據(jù)土壤發(fā)生學的理論,對東非黑棉土所屬土綱、黑色成因和主要膨脹性礦物來源等進行了研究。結(jié)果表明,東非黑棉土的黏粒含量高,液限和塑性指數(shù)高,自由膨脹率大,蒙脫石含量高,交換性陽離子數(shù)量大且以鈣離子為主,CBR值很小。東非黑棉土屬于典型的變性土,其中的蒙皂石族膨脹性礦物主要來源于中基性火山巖的原生和次生作用,其暗色主要來源于有機質(zhì)的嚴重浸染和含鐵蒙脫石。提出了改進的差分自由膨脹率指標和試驗方法,闡述了其微觀機理,進行了相關(guān)性分析并確定了膨脹勢分級標準。在分子模擬軟件中應用SPC/E位能模型、UFF力場、電荷平衡(QEq)算法和周期性邊界等建立體系;應用Skipper,chang以及Chavez-Paez等人的懷俄明蒙脫石參數(shù)構(gòu)建蒙脫石晶胞模型;采用Loewenstein規(guī)則處理蒙脫石中的類質(zhì)同象問題。在此基礎(chǔ)上,根據(jù)東非黑棉土和我國膨脹土的層間陽離子特征建立了三種蒙脫石構(gòu)型。通過分子力學對蒙脫石超晶胞進行了結(jié)構(gòu)優(yōu)化,隨后應用分子動力學模擬了在等溫等壓(NPT)系綜下蒙脫石超晶胞分子運動的穩(wěn)定狀態(tài),并通過徑向分布函數(shù)(RDF)對層間陽離子的水化狀態(tài)進行分析,進而分析了黑棉土的膨脹機理。由于蒙脫石礦物含量高且蒙脫石礦物層間的補償性陽離子增強了主要陽離子的水化能力,導致了東非黑棉土的強膨脹性。應用不同摻量的石灰、火山灰以及石灰+火山灰對東非黑棉土進行了化學處治,并對處治土的工程性質(zhì)進行了試驗和分析。結(jié)果表明,相較于石灰或火山灰的獨立處治技術(shù),石灰和火山灰聯(lián)合處治技術(shù)就可以取得更好的改性效果。3%石灰+15%火山灰的復配處治方案可以在降低工程造價的基礎(chǔ)上滿足《公路路基設(shè)計規(guī)范(JTGD30-2015)》的要求。結(jié)合計算機分子模擬研究、物相組成分析和工程性質(zhì)試驗的結(jié)果,提出了東非黑棉土改性的五大機理。
[Abstract]:In recent years, the engineering problems caused by the local black cotton soil are often encountered in the public and railway construction projects undertaken by China's Engineering Construction Group in East African countries. Because of the strong expansibility of the black cotton workers, the road engineering will cause serious diseases, so it is necessary to adopt the replacement scheme, which increases the engineering cost and earthwork quantity. An in-depth study on the expansion characteristics and treatment technology of the black cotton soil in East Africa can increase the safety of the project, reduce the cost of the project, and improve the environmental benefit. Relying on the public and railway projects of Chinese-funded enterprises in the East African region, the concept, harm, distribution, topography and climate characteristics of black cotton soil in East Africa were investigated in detail. With the aid of engineering investigation data and geotechnical field test, the engineering properties of black cotton soil in East Africa are analyzed. The basic engineering properties of undisturbed samples of black cotton soil in East Africa were tested and analyzed. According to the theory of soil genesis, the soil class, black origin and main expansive mineral sources of the black cotton soil in East Africa were studied. The results show that the clay content is high, the liquid limit and plasticity index is high, the free expansion rate is high, the content of montmorillonite is high, the quantity of exchangeable cations is large and Ca ~ (2 +) is dominant, and the CBR value is very small. The black cotton soil in East Africa belongs to the typical denatured soil, in which the expansive minerals of the Mongolian saponiferous group are mainly derived from the primary and secondary processes of the medium-basic volcanic rocks, and the dark color is mainly derived from the serious leaching of organic matter and the iron-bearing montmorillonite. The improved differential free expansion rate index and test method are put forward, the micro-mechanism is expounded, the correlation analysis is carried out, and the criterion of expansion potential classification is determined. In the molecular simulation software, SPC/E potential model, UFF force field, charge balance (QEq) algorithm and periodic boundary are used to establish the system, Skipper,chang and Chavez-Paez 's parameters of Wyoming montmorillonite are used to construct the cell model of montmorillonite. Loewenstein rule is used to deal with isomorphism in montmorillonite. On the basis of this, three montmorillonite configurations have been established according to the inter-layer cation characteristics of the black cotton soil in East Africa and the expansive soil in China. The structure of montmorillonite hyperfine cell was optimized by molecular mechanics. Then the molecular dynamics was used to simulate the stable state of the cell molecular movement of montmorillonite Shi Chao under isothermal and isobaric (NPT) system. The hydration state of interlayer cations was analyzed by radial distribution function (RDF), and then the swelling mechanism of black cotton soil was analyzed. Due to the high content of montmorillonite minerals and the compensatory cations between the layers of montmorillonite minerals, the hydration ability of the main cations is enhanced, which leads to the strong expansion of the black cotton soil in East Africa. In this paper, different amounts of lime, pozzolanic ash and lime pozzolanic ash were used to treat the black cotton soil in East Africa, and the engineering properties of the treated soil were tested and analyzed. The results show that compared with lime or pozzolanic ash, The combined treatment technology of lime and pozzolanic ash can obtain better modification effect, and the compound treatment scheme of 3% lime and 15% pozzolanic ash can meet the requirements of JTGD30-2015 (Design Code for Highway subgrade) on the basis of reducing the engineering cost. Based on the results of computer molecular simulation, phase composition analysis and engineering properties test, five mechanisms of modification of East African black cotton soil were put forward.
【學位授予單位】：東南大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U416.1
本文編號：2447036
[Abstract]:In recent years, the engineering problems caused by the local black cotton soil are often encountered in the public and railway construction projects undertaken by China's Engineering Construction Group in East African countries. Because of the strong expansibility of the black cotton workers, the road engineering will cause serious diseases, so it is necessary to adopt the replacement scheme, which increases the engineering cost and earthwork quantity. An in-depth study on the expansion characteristics and treatment technology of the black cotton soil in East Africa can increase the safety of the project, reduce the cost of the project, and improve the environmental benefit. Relying on the public and railway projects of Chinese-funded enterprises in the East African region, the concept, harm, distribution, topography and climate characteristics of black cotton soil in East Africa were investigated in detail. With the aid of engineering investigation data and geotechnical field test, the engineering properties of black cotton soil in East Africa are analyzed. The basic engineering properties of undisturbed samples of black cotton soil in East Africa were tested and analyzed. According to the theory of soil genesis, the soil class, black origin and main expansive mineral sources of the black cotton soil in East Africa were studied. The results show that the clay content is high, the liquid limit and plasticity index is high, the free expansion rate is high, the content of montmorillonite is high, the quantity of exchangeable cations is large and Ca ~ (2 +) is dominant, and the CBR value is very small. The black cotton soil in East Africa belongs to the typical denatured soil, in which the expansive minerals of the Mongolian saponiferous group are mainly derived from the primary and secondary processes of the medium-basic volcanic rocks, and the dark color is mainly derived from the serious leaching of organic matter and the iron-bearing montmorillonite. The improved differential free expansion rate index and test method are put forward, the micro-mechanism is expounded, the correlation analysis is carried out, and the criterion of expansion potential classification is determined. In the molecular simulation software, SPC/E potential model, UFF force field, charge balance (QEq) algorithm and periodic boundary are used to establish the system, Skipper,chang and Chavez-Paez 's parameters of Wyoming montmorillonite are used to construct the cell model of montmorillonite. Loewenstein rule is used to deal with isomorphism in montmorillonite. On the basis of this, three montmorillonite configurations have been established according to the inter-layer cation characteristics of the black cotton soil in East Africa and the expansive soil in China. The structure of montmorillonite hyperfine cell was optimized by molecular mechanics. Then the molecular dynamics was used to simulate the stable state of the cell molecular movement of montmorillonite Shi Chao under isothermal and isobaric (NPT) system. The hydration state of interlayer cations was analyzed by radial distribution function (RDF), and then the swelling mechanism of black cotton soil was analyzed. Due to the high content of montmorillonite minerals and the compensatory cations between the layers of montmorillonite minerals, the hydration ability of the main cations is enhanced, which leads to the strong expansion of the black cotton soil in East Africa. In this paper, different amounts of lime, pozzolanic ash and lime pozzolanic ash were used to treat the black cotton soil in East Africa, and the engineering properties of the treated soil were tested and analyzed. The results show that compared with lime or pozzolanic ash, The combined treatment technology of lime and pozzolanic ash can obtain better modification effect, and the compound treatment scheme of 3% lime and 15% pozzolanic ash can meet the requirements of JTGD30-2015 (Design Code for Highway subgrade) on the basis of reducing the engineering cost. Based on the results of computer molecular simulation, phase composition analysis and engineering properties test, five mechanisms of modification of East African black cotton soil were put forward.
【學位授予單位】：東南大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U416.1
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