止水帷幕对深基坑渗流场的影响

发布时间：2018-03-21 22:35

本文选题：悬挂式止水帷幕　切入点：深基坑降水　出处：《辽宁科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着经济建设的高速发展,深基坑工程应运而生,其中不乏大型深基坑。在深基坑设计及施工中,设置好止水帷幕是不可或缺的一环。绝大多数的止水帷幕设计都是为了获得最好的止水效果,而很少定量的研究止水帷幕作用下基坑的渗流特性。本文从渗流理论出发,对比分析了ANSYS软件中热分析模块原理和渗流基本理论的相似性,利用软件对基坑稳定渗流过程进行模拟,通过对比多种工况,用一系列数据分析止水帷幕对深基坑渗流场的影响,探讨止水帷幕在不同插入深度的工况下对基坑渗流场的影响。止水帷幕的深度不同,直接影响的就是渗流路径不同,在插入不透水层中的深度越大,渗流路径就越大,相对应的渗流场水头分布和水力坡降分布就会发生变化,而基坑以下水压过大会影响基底安全,发生突涌等危害,基底最大水力坡降值也会影响基坑的安全,本文通过模拟不同幕墙深度时基坑水头值变化分布及基底最大水力坡降值的变化,找出幕墙的关键深度。在单一均质土层中,在幕墙插入深度近似达到所在不透水层深度的25%时,基底以下水头值均达到最大;当插入深度达到不透水层的61%时,水头值与无止水帷幕时的水头值一致,当插入深入达到61%-99%时,基坑内所有水头值均小于无幕墙时的水头值,并依然在下降,才能真正起到降低水头的作用;止水帷幕深度的增加,对降低基坑内外水力坡降的作用非常明显,在幕墙深度增加到接近不透水层时,水力坡降的降低量能达到初始值的90%以上,效果显著,但它的降低值是先大幅度降低,在插入深度达到不透水的34%左右时,降低幅度变小,趋于平缓。结合北京华联深基坑的工程实例,模拟研究发现复杂土层中也存在与单一均质土层中相似的规律,证明了其现实存在性,也间接验证了ANSYS热分析模块在解决渗流问题上的可行性。
[Abstract]:With the rapid development of economic construction, deep foundation pit engineering emerges as the times require, among which there is no lack of large deep foundation pit. In the design and construction of deep foundation pit, It is indispensable to set up the waterproof curtain. Most of the watertight curtain design is to obtain the best sealing effect, but few quantitative research on the seepage characteristics of the foundation pit under the action of the waterproof curtain. This paper starts from the seepage theory. The similarity between the principle of thermal analysis module and the basic theory of seepage in ANSYS software is compared and the steady seepage process of foundation pit is simulated by software. A series of data are used to analyze the influence of the waterproof curtain on the seepage field of deep foundation pit, and the influence of the waterproof curtain on the seepage field of the deep foundation pit under different conditions of insertion depth is discussed. The greater the depth in the impermeable layer is, the larger the seepage path will be, and the corresponding seepage field water head distribution and hydraulic gradient distribution will change, and the water pressure below the foundation pit will affect the safety of the basement, causing sudden surge, and so on. The maximum hydraulic slope value of the base will also affect the safety of the foundation pit. In this paper, the critical depth of the curtain wall is found by simulating the variation distribution of the water head value of the foundation pit and the maximum hydraulic gradient value of the base under different curtain wall depths. When the insertion depth of the curtain wall reaches approximately 25 of the depth of the impervious layer, the water head value below the basement reaches the maximum; when the insertion depth reaches 61 percent of the impervious layer, the water head value is the same as the water head value when the impervious curtain is not in place. When the penetration depth reaches 61- 99%, all the water head values in the foundation pit are lower than those without curtain wall, and they are still decreasing. When the depth of curtain wall increases to close to impermeable layer, the decrease of hydraulic slope can reach more than 90% of the initial value, and the effect is remarkable. When the insertion depth reaches about 34% of impermeable depth, the decrease becomes smaller and tends to be gentle. Combined with the engineering example of deep foundation pit in Beijing Hualian, it is found that there are similar laws in the complex soil layer and in the single homogeneous soil layer. The feasibility of ANSYS thermal analysis module in solving seepage problem is proved.
【学位授予单位】：辽宁科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU463

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