随着城市建设的发展，基坑工程的设计和施工过程中，空间效应显得尤为重要。大量的工程实践表明，阳角基坑危险性更高，且随着基坑阳角角度的变化，其变形规律有所不同。因此，开展考虑空间效应下不同开挖角度对阳角基坑的受力特性及变形规律研究尤为重要。本文通过室内模型试验、数值模拟及理论计算相结合的方法，研究了阳角基坑不同开挖角度、不同长宽比对基坑侧壁变形的影响。主要研究成果如下：

根据空间效应产生机制和相似原理，确定模型试验相关参数，进行模型土的配比试验，确定出最佳配比，并安装监测设备对参数进行测定。

通过室内模型试验，研究三种工况（未支护阴角、排桩支护阴角、排桩支护阳角）下基坑的空间效应。在三种工况下，基坑侧壁水平位移均随着距离基坑角部越远逐渐增大，长边位移均大于短边，且阴、阳角基坑的变形均有显著的空间影响。随着基坑开挖的进行，桩侧土压力减小，长短边变化规律基本一致，且沿深度方向变化幅度较小。超载的影响仅在一定深度范围，深度越深、距离超载越远，影响越小。

采用数值方法建立与模型试验相对应的三维数值模型，确定数值模型的合理性。建立不同开挖角度及不同长宽比的阳角基坑计算模型，分析其对阳角基坑侧壁变形的影响，发现随着阳角基坑开挖角度的增大，基坑侧壁长边中部桩侧土压力整体的变化呈“阶梯状”；在90°、120°、150°三种开挖角度下，90°为最不利开挖角度；对以上各种工况进行总结分析，发现当长宽比为2：1时，开挖角度从90°增大到150°，空间效应影响区长度从2.85H减小到1.66H；开挖角度不变，基坑侧壁空间效应影响区长度随着长宽比的增大而增大。

在传统的土压力理论基础上，结合阳角型基坑的开挖角度，提出了可用于定量分析空间效应的阳角型基坑空间效应影响系数，从而更直接地分析出坑角效应的作用区域，从而为相似情况下基坑的支护设计提供一些理论依据。

With the development of urban construction, spatial effects are particularly important in the design and construction process of foundation pit engineering. A large number of engineering practices have shown that the danger of external corner excavation is higher, and the deformation law varies with the change of external corner angle of the excavation. Therefore, it is particularly important to conduct research on the stress characteristics and deformation laws of external corner foundation pits under different excavation angles considering spatial effects. This article combines indoor model tests, numerical simulations, and theoretical calculations to study the influence of different excavation angles and length to width ratios on the deformation of the side walls of the external corner foundation pit. The main research results are as follows:

(1)Based on the mechanism of spatial effects and the principle of similarity, determine the relevant parameters of the model test, conduct the ratio test of the model soil, determine the optimal ratio, and install monitoring equipment to measure the parameters.

(2)Through indoor model tests, the spatial effects of foundation pits under three working conditions (unsupported internal corners, row pile supported internal corners, and row pile supported external corners) were studied. Under three working conditions, the horizontal displacement of the side wall of the foundation pit gradually increases with the distance from the corner of the foundation pit, and the displacement of the long side is greater than that of the short side. Moreover, the deformation of the yin and yang corner foundation pits has significant spatial effects. As the excavation of the foundation pit progresses, the soil pressure on the pile side decreases, and the variation pattern of the long and short sides is basically consistent, and the variation amplitude along the depth direction is relatively small. The impact of overload is only within a certain depth range, and the deeper the depth and the farther away from overload, the smaller the impact.

(3)Establish a three-dimensional numerical model corresponding to the model experiment using numerical methods to determine the rationality of the numerical model. Establish a calculation model for external corner excavation with different excavation angles and length to width ratios, and analyze its impact on the deformation of the side wall of the external corner excavation. It is found that as the excavation angle of the external corner excavation increases, the overall change in soil pressure on the middle pile side of the long side of the excavation wall shows a "stepped" shape; At three excavation angles of 90°, 120°, and 150°, 90° is the most unfavorable excavation angle; After summarizing and analyzing the above various working conditions, it was found that when the aspect ratio is 2:1, the excavation angle increases from 90° to 150°, and the length of the spatial effect influence zone decreases from 2.85H to 1.66H; The excavation angle remains unchanged, and the length of the spatial effect zone on the side walls of the foundation pit increases with the increase of the aspect ratio.

(4) On the basis of traditional soil pressure theory and combined with the excavation angle of external angle type foundation pits, a spatial effect influence coefficient for external angle type foundation pits is proposed, which can be used for quantitative analysis of spatial effects. This allows for a more direct analysis of the action area of the pit angle effect and provides some theoretical basis for the support design of foundation pits in similar situations.

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