本文關鍵詞： 沉井 深厚軟土 固結沉降 結構計算 施工控制　出處：《浙江大學》2013年碩士論文　論文類型：學位論文

【摘要】：沉井是軟土地基中經(jīng)常采用的一種地下結構形式,其既可以作為一種基坑圍護結構單獨使用,也可作為主體結構的一部分,在工程領域有著廣泛的應用。尤其是在沿海大型火力發(fā)電廠的循環(huán)水系統(tǒng)建設中,循環(huán)水泵房的下部結構往往采用沉井結構,具有結構可靠、占地面積小、施工相對較簡單等特點。 本論文依托浙能樂清電廠循環(huán)水泵房大型雙沉井工程,分別采用三維有限元軟件ANSYS和二維有限元軟件分析了深厚軟土地基上大面積高填土堆載條件下雙沉井結構施工及竣工過程中受力規(guī)律,研究了內隔墻開設大型孔洞的情況下對沉井墻板的內力及變位分析的影響；采用巖土工程軟件PLAXIS研究了大面積堆載下地基固結沉降規(guī)律,以及雙沉井同步和不同步下沉,沉井的側向變形規(guī)律以及施工控制措施。通過以上研究,可以得出以下主要結論： 1)對沉井結構受力分析表明：在沉井的四個角點處的彎矩值均較大,中間部位縱橫隔墻處彎矩值相對較��；三維有限元軟件計算的沉井水平框架結構彎矩值約為二維桿系計算軟件計算值的70%-75%。 2)不管沉井橫隔墻孔洞是否采取臨時封堵措施,對沉井角點處的彎矩影響均不大,內力的重分配主要集中在孔洞周圍的墻板；開孔處是否采取封孔措施,對外側墻板的彎矩會發(fā)生改變,墻板跨中彎矩值變化幅度較小,支座處彎矩值變化較大,應在支座處進行加強。 3)沉井底板澆筑完成后,可以較大程度改善井體的受力結構,角點處水平向彎矩有較大幅度的下降,其余支座及跨中彎矩也有不同程度的降低。垂直向彎矩有不同程度的增加,尤其是跨中節(jié)點處增加明顯。 4)大面積堆載的情況下深厚軟土將產(chǎn)生3.0m的沉降量,采用PLAXIS巖土分析軟件計算結果與實測沉降比較一致。土體的開挖方式對于雙沉井的偏斜具有較大的控制作用,通過計算表明,井格內取土對井壁外土體產(chǎn)生較大的變位,總體趨勢是沉井刃腳向外側偏斜,沉井上部有靠攏趨勢,與實測的最終沉井變位相吻合。 5)采用不同的下沉方式,將對沉井的傾斜產(chǎn)生較大的差異。根據(jù)有限元模擬計算表明,雙沉井采用不同步下沉比同步下沉傾斜量約增加一倍。 6)由于土體的固結沉降,將對沉井及樁基產(chǎn)生較大的負摩阻力,在沉井下沉及底板澆筑過程中應充分考慮這一因素。在沉井刃腳部位采用注漿加固措施,可有效提高土體的承載力,對沉井的下沉穩(wěn)定具有一定的作用。同時還可減小土體的水平變位,防止樁頂側向擠壓破壞。
[Abstract]:Caisson is a kind of underground structure which is often used in soft soil foundation. It can be used either as a foundation pit retaining structure alone or as a part of the main structure. It is widely used in engineering field, especially in the construction of circulating water system in coastal large thermal power plant, the substructure of circulating water pump room often adopts caisson structure, which has reliable structure and small area. The construction is relatively simple and so on. This paper relies on Zhejiang Neng Yueqing Power Plant circulating Water pump House large-scale double-caisson project. Three dimensional finite element software ANSYS and two dimensional finite element software are used to analyze the stress law of double caisson structure under the condition of large area and high fill load on deep soft soil foundation. The influence of the opening of large holes on the internal force and displacement analysis of the wall board of the caisson is studied. By using geotechnical engineering software PLAXIS, the consolidation and settlement law of foundation under large area surcharge is studied, as well as synchronous and non-synchronous subsidence of double-caisson wells. The lateral deformation of the caisson and the construction control measures. Through the above study, we can draw the following main conclusions: 1) the stress analysis of the caisson structure shows that the moment values are larger at the four corners of the caisson, and the moment values are relatively small at the longitudinal and transverse walls in the middle part; The bending moment of horizontal frame structure calculated by 3D finite element software is about 70% of the calculated value of 2-D bar system calculation software. 2) no matter whether temporary sealing measures are adopted or not, the moment at the corner of the caisson is not affected, and the redistribution of internal force is mainly concentrated on the wall plate around the hole; The bending moment of the lateral wall will be changed when the hole opening is adopted or not. The variation range of the moment value in the middle span of the wall board is small, and the moment value at the support should be strengthened at the support. 3) after the bottom slab of the caisson is finished, the stress structure of the well body can be improved to a great extent, and the horizontal bending moment at the corner point can be decreased by a large margin. The other supports and the moment in the middle of the span also decreased to some extent, and the vertical moment increased in different degrees, especially at the node in the middle of the span. 4) under the condition of large area load, the settlement of the deep soft soil will be 3.0 m. The calculated results of PLAXIS geotechnical analysis software are consistent with the measured settlement. The excavation method of soil has a great control effect on the deflection of double-caisson, which is shown by calculation. There is a large displacement of soil outside the borehole wall by taking soil in the well space. The overall trend is that the edge foot of the caisson deviates to the outer side and the upper part of the caisson tends to close, which coincides with the measured displacement of the final caisson. 5) adopting different sinking modes will make great difference to the inclination of the caisson. According to the finite element simulation calculation, it is shown that the inclination of the double caisson adopting asynchronous subsidence is about twice as large as that of synchronous sinking. 6) due to the consolidation and settlement of soil, there will be great negative friction on the caisson and pile foundation, which should be fully considered in the sinking of the caisson and the pouring process of the bottom slab, and grouting reinforcement measures should be adopted at the edge and foot of the caisson. It can effectively improve the bearing capacity of soil, play a certain role in the sinking stability of the caisson, reduce the horizontal displacement of the soil, and prevent the lateral compression failure of the pile top.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2013
【分類號】：TU447;TU753

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