本文關鍵詞： 滲流溢出點 降水影響半徑 能量損失率 基坑涌水量　出處：《煙臺大學》2017年碩士論文　論文類型：學位論文

【摘要】：基坑涌水量計算是合理設計降水方案的關鍵,而確定降水影響半徑是計算基坑涌水量的關鍵。在現行規(guī)范中,降水影響半徑根據經驗公式計算,有時計算結果誤差較大。在水文地質條件已知的情況下,基坑滲流場可以簡化為Laplace方程的定解問題。理論上有限元法可以準確計算基坑滲流場,然而由于溢出邊界未知,無法在計算前對其定義,影響了計算精度。因此,求解溢出邊界是準確計算基坑滲流場降水半徑等參數的前提。論文對降水影響半徑等問題進行了研究,主要成果如下:(1)從能量角度出發(fā),提出基于能量損失率極大值確定滲流溢出點的一種方法,將使?jié)B流場水平方向能量損失率達到極大值的溢出點認定為真實溢出點。與虛單元法、等效滲透系數法、單元矩陣調整法等方法中溢出點的確定方法相比,本文方法有物理意義明確、不需迭代、容易收斂的優(yōu)點。(2)編制了能量損失率極大法計算穩(wěn)定滲流問題的有限元計算Fortran程序。利用該程序計算了有試驗解和解析解的二維、三維模型,所求溢出點與真實位置的相對誤差僅為1.29%、1.67%、0.98%;與節(jié)點虛流量法、初流量法、改進初流量法、改進截至負壓法、改進丟單元法計算的溢出點位置對比,本文算法的相對誤差較小,具有很高的精度。(3)通過對基坑涌水量計算模型的分析,降水影響半徑與滲流溢出點屬于滲流場模型的兩個相關變量,即在地下水位確定時,已知兩者中的一個就可以求解另一個。將基于能量損失率極大值確定滲流溢出點方法應用于基坑降水影響半徑的計算,對兩個基坑工程實例進行有限元數值計算,算得其降水影響半徑分別為37.23m、10.16m,以規(guī)范經驗公式計算的降水影響半徑為44.72m、32.17m,相對誤差分別為16.72%、68.42%。對影響穩(wěn)定滲流場中降水影響半徑的因素進行分析,探討了誤差產生的原因,提出以本文算法作為工程涌水量計算中降水影響半徑的計算方法。
[Abstract]:The calculation of foundation pit water discharge is the key to reasonable design of dewatering scheme, and the determination of the influence radius of precipitation is the key to calculate the water inflow of foundation pit. In the current code, the influence radius of dewatering is calculated according to empirical formula. When hydrogeological conditions are known, the seepage field of foundation pit can be simplified to a definite solution of Laplace equation. Theoretically, the finite element method can accurately calculate the seepage field of foundation pit. However, because the overflow boundary is unknown, it can not be defined before calculation, which affects the accuracy of calculation. The solution of overflow boundary is the premise of accurately calculating the parameters such as the radius of seepage field of foundation pit. The main results are as follows: 1) from the point of view of energy, the influence radius of precipitation is studied in this paper. A method of determining seepage overflow point based on the maximum value of energy loss rate is proposed. The overflow point which makes the energy loss rate of horizontal direction reach the maximum value is regarded as the true overflow point. Compared with the methods such as equivalent permeability coefficient method, element matrix adjustment method and so on, the method in this paper has clear physical meaning and does not need iteration. The advantage of easy convergence is to compile the Fortran program for the finite element calculation of the steady seepage problem by the maximum energy loss rate method. The program is used to calculate the two dimensional solutions with both experimental and analytical solutions. In 3D model, the relative error between the overflow point and the real position is only 1.29 and 1.670.98; Compared with node virtual flow method, initial flow method, improved initial flow method, improved end negative pressure method and improved unit loss method, the relative error of this algorithm is small. Through the analysis of the calculation model of foundation pit water inflow, the influence radius of precipitation and seepage overflow point belong to two related variables of seepage field model, that is, when the groundwater level is determined. One of the two is known to solve the other. The method of determining seepage overflow point based on the maximum of energy loss rate is applied to the calculation of the influence radius of foundation pit dewatering. The finite element numerical calculation of two foundation pit engineering examples shows that the influence radius of precipitation is 37.23 m / 10. 16 m, respectively, and the influence radius of precipitation is 44.72 m calculated by the standard empirical formula. 32.17m, the relative error is 16.72and 68.42.The factors influencing the influence radius of precipitation in the steady seepage field are analyzed, and the causes of the errors are discussed. This paper presents a method for calculating the influence radius of precipitation in the calculation of engineering water inflow.
【學位授予單位】：煙臺大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU753

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