Abstract: The plane shape, size of the excavation and embedment depth of the retaining wall all affect the heave-resistant stability of excavations. However, the influence of above factors can’t be comprehensively expressed by the calculation methods of safety coefficient of heave-resistant stability recommended from existing standards and codes. In order to solve this problem and differentiate the situations, the possible failure modes of basal heave are classified; and thereby the corresponding formulas calculating the safety coefficient of heave-resistant stability under different failure modes are given. Based on this method, the heave-resistant stability of excavations will be influenced by the strength, stiffness and embedment depth of the retaining wall. The calculation analyses indicate that, for both the drained and undrained situation, the narrow excavations are more stable than wide ones, and that the stability can be improved by adjusting the embedment depth of the retaining wall. The improved excavation safety factor, can take more factors into account, which provides a theoretical method to reduce the embedded depths of the retaining wall of narrow excavations.

Key words: excavation, heave-resistant stability, size, excavation width, the embedded depth