發(fā)布時(shí)間：2018-07-05 11:21

  本文選題：基坑 + 凍土擋墻��； 參考：《吉林大學(xué)》2015年博士論文

【摘要】：國(guó)家經(jīng)濟(jì)不斷騰飛，社會(huì)發(fā)展速度不斷加快，大型建筑、大型基建項(xiàng)目正不斷的上馬，但與此同時(shí)帶來了地下工程支護(hù)的諸多問題。已有的支護(hù)方案不僅造成后續(xù)工程的無法順利進(jìn)行，同時(shí)由于支護(hù)的原因，造成大量的建筑廢棄物，如土釘墻、樁錨支護(hù)中的鋼筋無法取出再使用，而且在支護(hù)前的大量降水止水過程，不僅改變了地下水位的位置，由于鋼筋的腐蝕也造成了地下水的污染。因此，地下支護(hù)的改變成為了十分突出的問題。 基坑凍土擋墻在支護(hù)過程中不受地質(zhì)條件限制，只需通過人工凍結(jié)技術(shù)使土體凍結(jié)，就可以使土體的抵抗外力的能力增強(qiáng)，在強(qiáng)度上達(dá)到設(shè)計(jì)要求。基坑凍土擋墻不僅可以起到支護(hù)作用，而且冰可以有效的阻擋水的滲流，起到止水的效果。基坑凍土擋墻具有的諸多優(yōu)點(diǎn)，保證了在不改變地下水條件下，仍可以保證基礎(chǔ)施工的順利進(jìn)行。在凍土的自然融解后，恢復(fù)原有的地層情況。由于沒有建筑廢棄物的存在，不會(huì)對(duì)地下水產(chǎn)生污染，另外不會(huì)影響周圍的地下管線，不會(huì)對(duì)建筑物周圍的建設(shè)造成后期的影響，且可以循環(huán)使用，不會(huì)造成經(jīng)濟(jì)上的浪費(fèi)。對(duì)比以往的支護(hù)方案，基坑凍土擋墻的優(yōu)勢(shì)非常明顯，越來越成為施工人員選擇的施工方法。 然而，不論是施工人員還是設(shè)計(jì)人員，對(duì)于該施工方法不甚了解。盡管在礦井建設(shè)上已經(jīng)使用人工凍結(jié)技術(shù)多年，并且形成的理論相當(dāng)成熟，但作為基坑支護(hù)的一種施工方法使用還是很少。原因是基坑凍土擋墻在基坑中的支護(hù)缺少理論研究，不能為基坑凍土擋墻做理論支持。比如凍土擋墻強(qiáng)度理論的貧乏、凍土溫度場(chǎng)發(fā)展規(guī)律計(jì)算復(fù)雜、凍土溫度場(chǎng)計(jì)算機(jī)輔助時(shí)人為因素過多影響模型性質(zhì)、制冷循環(huán)系統(tǒng)的溫度控制以及遠(yuǎn)端無線操控的研究等。本文通過現(xiàn)場(chǎng)模擬試驗(yàn)、數(shù)值模擬分析等方法對(duì)基坑凍土擋墻強(qiáng)度的影響因素進(jìn)行理論分析及數(shù)值分析，找到強(qiáng)度的變化拐點(diǎn)，以能量守恒定律為基礎(chǔ)，利用數(shù)值分析的方法研究基坑凍土擋墻冷凍半徑的發(fā)展規(guī)律，自制較為簡(jiǎn)單的溫度測(cè)控系統(tǒng)。以下是研究的主要內(nèi)容及主要成果： （1）通過凍結(jié)試驗(yàn)裝置進(jìn)行模擬試驗(yàn)，分析了粉質(zhì)粘土在不同含水率下，凍結(jié)強(qiáng)度與深度、徑向距離、凍結(jié)時(shí)間、凍結(jié)溫度間等的強(qiáng)度變化規(guī)律�；觾鐾翐鯄Φ膹�(qiáng)度在含水率和凍結(jié)溫度上都存在拐點(diǎn)。含水率低于拐點(diǎn)值時(shí)，凍土擋墻的抗壓強(qiáng)度、抗拉強(qiáng)度、抗剪強(qiáng)度及壓入硬度都隨溫度的降低而增高，但含水率高于拐點(diǎn)值時(shí)，變化趨勢(shì)相反或變化不大。當(dāng)含水率一定時(shí)，凍土的壓入硬度在土體溫度低于拐點(diǎn)值時(shí)不再繼續(xù)增高或增高緩慢，凍土擋墻的抗壓強(qiáng)度、抗拉強(qiáng)度及抗剪強(qiáng)度在土體溫度低于拐點(diǎn)值時(shí)，反而隨溫度的降低而降低。 （2）以能量守恒定律為基礎(chǔ)，對(duì)凍土溫度場(chǎng)進(jìn)行數(shù)值模擬研究，得到運(yùn)算簡(jiǎn)單、精度更高的基坑凍土擋墻凍土溫度場(chǎng)發(fā)展規(guī)律的數(shù)學(xué)模型。模型解決了傳熱學(xué)溫度場(chǎng)凍土模型建立的困難和對(duì)復(fù)雜偏微分方程組的求解；解決了采用ANSYS有限元分析法時(shí)，由于在凍土建模時(shí)控制參數(shù)選取受到人為主觀因素的影響較大而經(jīng)常出現(xiàn)分析解算結(jié)果與實(shí)際不符的情況。通過與現(xiàn)場(chǎng)試驗(yàn)得到的數(shù)據(jù)對(duì)比分析，模擬的凍土溫度場(chǎng)變化規(guī)律的發(fā)展擬合曲線走勢(shì)大致與試驗(yàn)數(shù)據(jù)所得到的擬合曲線相近，吻合度較高。 （3）以主處理器AT89S52為核心制作單片機(jī)，建立溫度測(cè)控系統(tǒng)。溫控系統(tǒng)包含測(cè)溫系統(tǒng)與溫度控制系統(tǒng)。經(jīng)過對(duì)多個(gè)單探頭測(cè)溫傳感器與溫度測(cè)溫系統(tǒng)的測(cè)試對(duì)比分析，該套溫度測(cè)試系統(tǒng)在溫度自動(dòng)采集的使用中可行，且準(zhǔn)確率較高。利用測(cè)溫系統(tǒng)對(duì)溫度進(jìn)行采集，把溫度信號(hào)傳送到溫度控制系統(tǒng)，通過溫度控制系統(tǒng)對(duì)工作泵進(jìn)行控制，在溫度達(dá)到要求是關(guān)閉工作泵，停止輸送制冷液，溫度超過范圍時(shí)，自動(dòng)打開工作泵，，制冷液開始循環(huán)流動(dòng)。通過現(xiàn)場(chǎng)試驗(yàn)，該設(shè)備可準(zhǔn)確的控制工作泵運(yùn)轉(zhuǎn)。以無線通信傳輸模式為基礎(chǔ)，通過無線通訊協(xié)議制作無線傳輸設(shè)備，并把無線設(shè)備與自動(dòng)溫控系統(tǒng)連接，然后通過接口軟件把無線傳輸設(shè)備與計(jì)算機(jī)進(jìn)行連接，編寫計(jì)算機(jī)軟件，利用計(jì)算機(jī)在遠(yuǎn)端無線控制自動(dòng)測(cè)溫系統(tǒng)，通過現(xiàn)場(chǎng)試驗(yàn)效果良好。
[Abstract]:The national economy is constantly soaring, the speed of social development is speeding up, large buildings and large infrastructure projects are coming up continuously, but at the same time it brings many problems in the support of underground engineering. The existing support schemes not only cause the failure of the follow-up projects, but also cause a large amount of construction waste, such as soil nails, due to the reasons of support. The steel bars in the pile and anchor support can not be taken out and reused, and a large number of precipitation and stopping processes before the support not only change the position of the groundwater level, but also cause the pollution of the groundwater. Therefore, the change of underground support has become a very prominent problem.
The frozen soil retaining wall in the foundation pit is not restricted by the geological conditions in the supporting process. The soil can be frozen by artificial freezing technology, which can enhance the ability of the soil to resist external force and meet the design requirements. The frozen soil retaining wall can not only play a supporting role, but also can effectively block the seepage of water and play an effective way to stop the water. There are many advantages of the permafrost retaining wall, which ensures the smooth progress of the foundation construction without changing the ground water conditions. After the natural melting of the frozen soil, the original formation situation will be restored. Because there is no construction waste, it will not be contaminated with groundwater, and the surrounding underground pipelines will not be affected. The influence on the construction around the building, and it can be used circulate, will not cause the waste of economy. Compared with the previous support scheme, the advantages of the frozen soil retaining wall in the foundation pit are very obvious, and more and more become the construction methods chosen by the constructors.
However, the constructors and designers are not very familiar with the construction method. Although artificial freezing technology has been used for many years in the mine construction, and the theory is quite mature, the use of a construction method as a foundation pit support is still very few. The reason is that the support for the frozen soil retaining wall in the foundation pit is lack of theory. The research can not provide theoretical support for the permafrost retaining wall of the foundation pit, such as the lack of the permafrost wall strength theory, the complexity of the temperature field development of the permafrost, the overabundance of artificial factors, the temperature control of the refrigeration cycle system and the research on the remote wireless manipulation of the refrigeration cycle system. Theoretical analysis and numerical analysis on the influence factors of the strength of frozen soil retaining wall in foundation pit are analyzed and analyzed by numerical simulation analysis, and the changing inflection point of strength is found. Based on the law of conservation of energy, the development law of frozen radius of frozen soil retaining wall in foundation pit is studied by means of numerical analysis, and the simple temperature measurement and control system is made by ourselves. The following is the research of the temperature measurement system. The main contents and main achievements of the study are as follows:
(1) through the simulation test of the freezing test device, the strength changes of the freezing strength and depth, the radial distance, the freezing time and the freezing temperature are analyzed under the different water content. The strength of the frozen soil retaining wall in the foundation pit is in the inflection point at the water content and the freezing temperature. The compression of the frozen soil retaining wall is lower than the water cut point. Strength, tensile strength, shear strength and indentation hardness increase with the decrease of temperature, but when the water content is higher than the inflection point, the change trend is opposite or little. When the water content is certain, the compressive hardness of the frozen soil no longer increases or increases slowly when the soil temperature is lower than the inflection point, and the compressive strength, tensile strength and resistance of the permafrost retaining wall. When the soil temperature is lower than the inflection point, the shear strength decreases with the decrease of temperature.
(2) on the basis of the law of conservation of energy, the mathematical model of the temperature field of frozen soil is numerically simulated to obtain the mathematical model of the development law of frozen soil temperature field in frozen soil retaining wall with simple operation and higher precision. The model solves the difficulty of establishing the frozen soil model in the heat transfer temperature field and solving the complex partial differential equations, and solves the problem of using ANSYS. In the finite element analysis method, the control parameter selection is greatly influenced by the subjective factors in the frozen soil modeling, and the analysis results are often inconsistent with the actual conditions. Through the comparison and analysis of the data obtained from the field test, the trend of the simulation curve of the simulated temperature field variation of frozen soil is roughly with the experimental data. The fitting curves are close, and the degree of anastomosis is high.
(3) the temperature measurement and control system is set up with the main processor AT89S52 as the core. The temperature control system includes the temperature measurement system and the temperature control system. After comparing and analyzing the test of the temperature measuring system with a number of single probe sensors, the temperature measurement system is feasible in the use of temperature auto acquisition, and the accuracy is high. The temperature measurement system can collect the temperature, transmit the temperature signal to the temperature control system and control the working pump through the temperature control system. When the temperature is reached, the working pump is closed, the refrigerating liquid is stopped and the temperature exceeds the range. The working pump is opened automatically and the refrigeration liquid begins to circulate. Through field test, the equipment can be accurate. Control work pump operation. Based on wireless communication transmission mode, wireless transmission equipment is produced by wireless communication protocol, and wireless devices are connected with automatic temperature control system. Then wireless transmission equipment is connected to computer through interface software, computer software is written, and automatic temperature measurement is used by computer in remote wireless control. The system has a good effect through the field test.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU476.4

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