人工凍結(jié)海相軟土凍脹特性研究
發(fā)布時間：2019-01-27 10:48
【摘要】：我國沿海地區(qū)廣泛分布著深厚的海相沉積軟土層,人工地層凍結(jié)技術(shù)作為一種地層加固技術(shù),可以有效地解決海相軟土強(qiáng)度低、蠕變性、觸變性等工程性質(zhì)差的難題。但是,在海相軟土層中應(yīng)用人工地層凍結(jié)技術(shù),一方面其熱物理與力學(xué)參數(shù)研究較少,缺少相應(yīng)的基礎(chǔ)數(shù)據(jù),另一方面,人工凍結(jié)海相軟土凍脹特性的研究尚處于空白狀態(tài)。為了滿足海相軟土地層應(yīng)用人工地層凍結(jié)技術(shù)的需要,本文采用室內(nèi)試驗(yàn)、理論推導(dǎo)與數(shù)值模擬相結(jié)合的研究方法,對人工凍結(jié)條件下海相軟土的凍脹特性開展了一系列研究。首先,通過室內(nèi)試驗(yàn)對人工凍結(jié)條件下海相軟土的熱物理與力學(xué)參數(shù)進(jìn)行研究。海相軟土由于受到海水的入侵,導(dǎo)致其內(nèi)部含有一定量的易溶鹽。在對寧波地區(qū)兩種典型的海相軟土層進(jìn)行室內(nèi)含鹽量測定的基礎(chǔ)上,研究了海相軟土的起始凍結(jié)溫度、導(dǎo)熱系數(shù)、凍土比熱、凍土彈性模量及凍土單軸抗壓強(qiáng)度等熱物理與力學(xué)參數(shù),得出了不同影響因素對海相軟土熱物理與力學(xué)參數(shù)的影響規(guī)律。其次,通過室內(nèi)凍脹試驗(yàn)對人工凍結(jié)條件下海相軟土的凍脹特性開展研究。在自行設(shè)計(jì)并加工的一套簡易的室內(nèi)凍脹試驗(yàn)裝置上,開展凍脹率單因素試驗(yàn)與凍脹率正交試驗(yàn)。室內(nèi)凍脹試驗(yàn)是自下而上一維凍結(jié)條件下進(jìn)行的,測出土體試樣的凍脹量,凍脹率通過計(jì)算得到,并得出了含鹽量、含水率、冷端溫度、外部荷載四個因素對海相軟土凍脹率的影響規(guī)律以及四個因素之間的主次關(guān)系。同時,通過對凍脹試驗(yàn)過程中溫度監(jiān)測及凍結(jié)后土體試樣不同部位含水率的測量,得出試驗(yàn)過程中溫度場的發(fā)展規(guī)律與水分重分布的規(guī)律。再者,考慮了海相軟土降溫凍結(jié)過程中二次相變的現(xiàn)象,對已有的水分場、鹽分場、溫度場以及應(yīng)力場方程進(jìn)行了修正,建立了人工凍結(jié)海相軟土水-鹽-熱-力四場耦合的凍脹預(yù)報(bào)模型。最后,在對已建立的凍脹預(yù)報(bào)模型進(jìn)行合理簡化之后,通過有限元數(shù)值模擬軟件COMSOL二次開發(fā)中的PDE模塊,對已建立的凍脹預(yù)報(bào)模型進(jìn)行了求解計(jì)算,從而實(shí)現(xiàn)了對已建立的凍脹預(yù)報(bào)模型的驗(yàn)證。將數(shù)值模擬的計(jì)算結(jié)果與室內(nèi)凍脹試驗(yàn)的測量結(jié)果進(jìn)行了對比,二者相互印證了本文對人工凍結(jié)條件下海相軟土凍脹特性規(guī)律研究的正確性。
[Abstract]:Deep marine sedimentary soft soil is widely distributed in coastal areas of China. As a kind of stratum strengthening technology, artificial stratum freezing technology can effectively solve the problems of low strength, creep, thixotropy and other engineering properties of marine soft soil. However, in the application of artificial stratum freezing technology in marine soft soil, on the one hand, the study of thermal physical and mechanical parameters is less, and the corresponding basic data is lacking; on the other hand, the research on the frost heave characteristics of artificial frozen marine soft soil is still in blank state. In order to meet the need of applying artificial formation freezing technology in marine soft soil, this paper has carried out a series of research on the frost heave characteristics of marine soft soil under artificial freezing condition by means of laboratory test, theoretical derivation and numerical simulation. Firstly, the thermal physical and mechanical parameters of marine soft soil under artificial freezing condition were studied. Due to the invasion of sea water, marine soft soil contains a certain amount of soluble salt. Based on the indoor measurement of salt content in two typical marine soft soil layers in Ningbo area, the initial freezing temperature, thermal conductivity and specific heat of frozen soil are studied. The thermal physical and mechanical parameters such as elastic modulus of frozen soil and uniaxial compressive strength of frozen soil are obtained. The influence of different factors on the thermal physical and mechanical parameters of marine soft soil is obtained. Secondly, the frost heaving characteristics of marine soft soil under artificial freezing condition are studied by indoor frost heaving test. The single factor test and orthogonal test of frost heave rate were carried out on a set of simple indoor frost heave test device designed and processed by ourselves. The indoor frost heave test was carried out under the condition of one-dimensional freezing from bottom to top. The frost heave quantity of soil sample was measured, and the frost heave rate was calculated, and the salt content, moisture content and cold end temperature were obtained. The influence of four factors of external load on the frost heaving rate of marine soft soil and the primary and secondary relationship between the four factors. At the same time, through the temperature monitoring during the frost heave test and the measurement of moisture content in different parts of the frozen soil sample, the development law of the temperature field and the law of water redistribution during the test process are obtained. Furthermore, considering the phenomenon of secondary phase transition in the process of cooling and freezing of marine soft soil, the existing equations of water field, salt field, temperature field and stress field are modified. The frost heaving prediction model of artificial frozen marine soft soil is established in this paper, which is coupled with water, salt, heat and force. Finally, after reasonable simplification of the established frost heave prediction model, the established frost heave prediction model is solved by the PDE module in the secondary development of the finite element numerical simulation software COMSOL. Thus the verification of the established frost heave prediction model is realized. The calculated results of numerical simulation are compared with the measured results of indoor frost heave test. Both of them confirm the correctness of the research on the frost heave characteristics of marine soft soil under artificial freezing condition.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU447
本文編號：2416187
[Abstract]:Deep marine sedimentary soft soil is widely distributed in coastal areas of China. As a kind of stratum strengthening technology, artificial stratum freezing technology can effectively solve the problems of low strength, creep, thixotropy and other engineering properties of marine soft soil. However, in the application of artificial stratum freezing technology in marine soft soil, on the one hand, the study of thermal physical and mechanical parameters is less, and the corresponding basic data is lacking; on the other hand, the research on the frost heave characteristics of artificial frozen marine soft soil is still in blank state. In order to meet the need of applying artificial formation freezing technology in marine soft soil, this paper has carried out a series of research on the frost heave characteristics of marine soft soil under artificial freezing condition by means of laboratory test, theoretical derivation and numerical simulation. Firstly, the thermal physical and mechanical parameters of marine soft soil under artificial freezing condition were studied. Due to the invasion of sea water, marine soft soil contains a certain amount of soluble salt. Based on the indoor measurement of salt content in two typical marine soft soil layers in Ningbo area, the initial freezing temperature, thermal conductivity and specific heat of frozen soil are studied. The thermal physical and mechanical parameters such as elastic modulus of frozen soil and uniaxial compressive strength of frozen soil are obtained. The influence of different factors on the thermal physical and mechanical parameters of marine soft soil is obtained. Secondly, the frost heaving characteristics of marine soft soil under artificial freezing condition are studied by indoor frost heaving test. The single factor test and orthogonal test of frost heave rate were carried out on a set of simple indoor frost heave test device designed and processed by ourselves. The indoor frost heave test was carried out under the condition of one-dimensional freezing from bottom to top. The frost heave quantity of soil sample was measured, and the frost heave rate was calculated, and the salt content, moisture content and cold end temperature were obtained. The influence of four factors of external load on the frost heaving rate of marine soft soil and the primary and secondary relationship between the four factors. At the same time, through the temperature monitoring during the frost heave test and the measurement of moisture content in different parts of the frozen soil sample, the development law of the temperature field and the law of water redistribution during the test process are obtained. Furthermore, considering the phenomenon of secondary phase transition in the process of cooling and freezing of marine soft soil, the existing equations of water field, salt field, temperature field and stress field are modified. The frost heaving prediction model of artificial frozen marine soft soil is established in this paper, which is coupled with water, salt, heat and force. Finally, after reasonable simplification of the established frost heave prediction model, the established frost heave prediction model is solved by the PDE module in the secondary development of the finite element numerical simulation software COMSOL. Thus the verification of the established frost heave prediction model is realized. The calculated results of numerical simulation are compared with the measured results of indoor frost heave test. Both of them confirm the correctness of the research on the frost heave characteristics of marine soft soil under artificial freezing condition.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU447
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