改进的浅埋隧道松动围岩压力计算方法

An Improved Method to Calculate the Loosening Earth Pressure on Shallow Tunnels

对浅埋隧道,松动围岩压力经典理论的计算结果差异显著,且在某些假定上存在不足。本文克服了经典理论假定上的不足,建立了实用的松动压力公式。该公式计算的松动压力随埋深、黏聚力、内摩擦角等参数的变化均符合一般规律。该公式随埋深变化具有极大值,这一特征与岩柱理论、谢家烋公式类似。该公式可以用于内摩擦角φ≤45°的一般土质隧道,当φ≤10°时,该公式计算值与Terzaghi公式计算值差别微小。实测数据和对土柱的理论分析表明:松动压力的理论最大值为岩柱理论计算值。本文公式与Terzaghi公式计算值小于最大值,谢家烋公式计算值大于最大值。该公式对浅埋土质隧道和松散破碎的岩石隧道具有重要的参考价值。

For shallow tunnels, classic theories of surrounding rock loosening pressures differ notably in calcu-lated results and are deficient in setting of some assumptions. In this paper overcoming assumption deficiencies from the classic theories, the practical formula of loosening pressures was deduced, which provided a new theo-retical foundation for the arching effect of tunnels. With the formula, changes of loosening pressures with the buried depth, cohesion and internal friction angle accorded with the general law. The formula presented the macimum point pressures along with changing of the buried depth, this characteristic being similar to the rock pillar theory （Bierbaumer＇s theory） and Xie Jiaxiu＇s formula. The formula was able to be applied in the case of ordinary soil tunnels of the internal friction angle φ≤45°, and when φ≤10°, the calculated result of the formula was slightly different from that of the Terzaghi＇s theory. Theoretical analysis on soil pillars and measured data indicate that the theoretical maximum value of loosening pressure should be the calculated value of the rock pil- lar theory. The calculated value of the presented formula and Terzaghi＇s theory are both smaller than the max-imum value whereas the calculated value of the Xie Jiaxiu＇s formula is larger than the maximum value. There-fore, the proposed formula is an important reference to building of shallow earth tunnels and loose broken rock tunnels.