复杂环境基坑周边空间愈加有限,经典土压力理论所假设的半无限空间与实际工程不符,使得有限土体基坑主动土压力仍缺乏合理的计算方法。以有限土体基坑柔性围护桩和砂土为研究对象,采用单排桩悬臂支护模式且围护桩底端固定,开展了四种不同土体宽度下的基坑开挖模型试验,以探究主动土压力和围护桩水平位移沿围护桩分布特征。结果表明:各土体宽度侧支护结构水平位移近似三角形变位模式,土压力随开挖深度增大逐渐近似“D”型分布,最大值约出现在0.8H深度位置。通过极限平衡法对土体微分单元进行受力分析,推导极限状态下有限土体主动土压力分布,结合考虑位移影响的摩擦角发挥模型,推导了有限土体非极限主动土压力分布、合力大小以及作用点高度。通过土压力试验值和本文理论值的对比,验证了本文计算方法的有效性。经参数分析发现土压力与宽高比正相关,与内摩擦角负相关,区分有限土体与半无限土体的临界宽高比ncr = 0.5。
The space around the proposed excavation in complex environments becomes increasingly limited, the semi-infinite space assumed by the classical earth pressure theory is inconsistent with actual engineering, resulting in a lack of reasonable calculation methods for active earth pressure in excavations with limited soil. Taking the flexible retaining piles and sandy soil of limited soil excavations as the research objects, using the single-row pile cantilever retaining mode and the bottom ends of the retaining piles fixed, four excavations model tests under different soil widths were carried out. To explore the distribution characteristics of active earth pressure and horizontal displacement of retaining piles along the retaining piles. The results show that the horizontal displacement of the retaining structure on each soil width side approximates a triangular displacement pattern, and the earth pressure gradually approximates a D-shaped distribution as the excavation depth increases, with the maximum value appearing at approximately 0.8H depth. The force analysis of the soil differential unit was performed through the limit equilibrium method, and the active earth pressure distribution of the finite soil under the limit state was deduced. Combined with the friction angle development model that considers the influence of displacement, the non-limit active earth pressure distribution and resultant force of the finite soil were deduced. and the height of the point of action. The effectiveness of the calculation method in this paper is verified by comparing the earth pressure test values with the theoretical values in this paper. Through parameter analysis, it was found that the earth pressure is positively related to the aspect ratio and negatively related to the internal friction angle. The critical aspect ratio ncr = 0.5 to distinguish between finite soil and semi-infinite soil.
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