## 3 Measured Uplift Pressure Application Method and Software Development
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Application Method** & **Assumption** & **Problems** \\ \hline \multirow{4}{*}{Face force} & Compared with the rock foundation with cracks and joints, the permeability coefficient of concrete is several small orders of magnitude. So the seepage pressure not far from the concrete facing water surface will quickly decay. The uplift pressure is mainly concentrated on the concrete surface [38]. & There is a gap between the assumption that the concrete permeability coefficient is minimal and the actual situation. \\  & The concrete and rock mass are both water-permeable materials. After the formation of stable seepage, the infiltration line of the gravity dam body adopts the uplift pressure distribution curve. The uplift pressure is applied by using the submerged unit weight of the concrete below the infiltration line [2]. & The treatment with different unit weight lacks a theoretical, which is not applicable to arch dams [38]. \\  & The seepage field of the foundation is obtained in advance, so the uplift pressure on the foundation surface can be calculated to apply to the dam calculation model [39]. The denser the distribution of equal headlines on the impervious curtain and sliding surface, the greater the seepage pressure [40]. & The seepage field of the foundation-dam should be calculated separately. \\  & Through clarifying the interaction mechanism between seepage and stress field, the impervious curtain studies the fluid-solid coupling mechanism of the foundation-dam [41]. Through the FEM, the stress field, displacement field [42], and seepage field [43] of the foundation-dam can be obtained simultaneously. & Multi-field coupling calculation has a large workload and complex mechanism [44]. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main methods of applying uplift pressure in FEM simulation. curve, positioning integration points, and numerical interpolation, a limited number of measured uplift pressure are converted into uplift pressure values of each element in the dam foundation. Through this method, the rapid conversion from original monitoring data to numerical simulation boundary conditions is realized. The structural behavior of the concrete dam, under design and measured uplift pressure, can be analyzed accurately and quickly. The flow chart of the application method of measured uplift pressure is shown in Figure 3.  
According to Figure 3, the calculation steps of the application method of measured uplift pressure are as follows:  
1. All kinds of essential data are inputted, including the upstream water level, the shape, and elevation of dam foundation surface, the coordinate of drainage pipe, the coordinate of integration points of foundation surface in finite element model, and other necessary data. 2. Influenced by the actual topography, the foundation surface's boundary and the drainage pipe's position line, formed by the intersection of the dam body and dam foundation, are irregular. To facilitate the positioning calculation of integration points, it is necessary to construct the fitting curve equation of the boundary and the position. Through different projects, the quartic polynomial shows a better-fit effect to meet the needs of subsequent calculation. 3. Selecting an integration point of an element in the FEM model, the relationship between the integration point and the water level is judged. If this integration point is below the water level, the following calculation step is to proceed. Otherwise, the uplift force of this integration point is set equal to zero. Figure 3: Flow chart of the application method of measured uplift pressure. The positional relationship between the integration point and the drainage pipe is judged and divided into the upstream and the downstream integration point. Then, to determine the position of the integration point in the cross-section, the inner normal between the integration point and the foundation boundary is searched, of which the slope, distance, and foot of a perpendicular are calculated.