深厚软土地基大型双沉井结构设计及施工控制

发布时间：2018-01-24 00:42

本文关键词： 沉井深厚软土固结沉降结构计算施工控制　出处：《浙江大学》2013年硕士论文　论文类型：学位论文

【摘要】：沉井是软土地基中经常采用的一种地下结构形式,其既可以作为一种基坑围护结构单独使用,也可作为主体结构的一部分,在工程领域有着广泛的应用。尤其是在沿海大型火力发电厂的循环水系统建设中,循环水泵房的下部结构往往采用沉井结构,具有结构可靠、占地面积小、施工相对较简单等特点。本论文依托浙能乐清电厂循环水泵房大型双沉井工程,分别采用三维有限元软件ANSYS和二维有限元软件分析了深厚软土地基上大面积高填土堆载条件下双沉井结构施工及竣工过程中受力规律,研究了内隔墙开设大型孔洞的情况下对沉井墙板的内力及变位分析的影响；采用岩土工程软件PLAXIS研究了大面积堆载下地基固结沉降规律,以及双沉井同步和不同步下沉,沉井的侧向变形规律以及施工控制措施。通过以上研究,可以得出以下主要结论： 1)对沉井结构受力分析表明：在沉井的四个角点处的弯矩值均较大,中间部位纵横隔墙处弯矩值相对较小；三维有限元软件计算的沉井水平框架结构弯矩值约为二维杆系计算软件计算值的70%-75%。 2)不管沉井横隔墙孔洞是否采取临时封堵措施,对沉井角点处的弯矩影响均不大,内力的重分配主要集中在孔洞周围的墙板；开孔处是否采取封孔措施,对外侧墙板的弯矩会发生改变,墙板跨中弯矩值变化幅度较小,支座处弯矩值变化较大,应在支座处进行加强。 3)沉井底板浇筑完成后,可以较大程度改善井体的受力结构,角点处水平向弯矩有较大幅度的下降,其余支座及跨中弯矩也有不同程度的降低。垂直向弯矩有不同程度的增加,尤其是跨中节点处增加明显。 4)大面积堆载的情况下深厚软土将产生3.0m的沉降量,采用PLAXIS岩土分析软件计算结果与实测沉降比较一致。土体的开挖方式对于双沉井的偏斜具有较大的控制作用,通过计算表明,井格内取土对井壁外土体产生较大的变位,总体趋势是沉井刃脚向外侧偏斜,沉井上部有靠拢趋势,与实测的最终沉井变位相吻合。 5)采用不同的下沉方式,将对沉井的倾斜产生较大的差异。根据有限元模拟计算表明,双沉井采用不同步下沉比同步下沉倾斜量约增加一倍。 6)由于土体的固结沉降,将对沉井及桩基产生较大的负摩阻力,在沉井下沉及底板浇筑过程中应充分考虑这一因素。在沉井刃脚部位采用注浆加固措施,可有效提高土体的承载力,对沉井的下沉稳定具有一定的作用。同时还可减小土体的水平变位,防止桩顶侧向挤压破坏。
[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.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU447;TU753

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