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In the process of construction, it is essential to determine the surrounding rock pressure, which needs to propose the simulation model according to relevant theory, and calculate and analyze the surrounding rock stress, to guarantee the safety of the tunnel construction and operation. However, this has been no perfect calculation theory and formula for surrounding rock stress to unsymmetrically loading tunnel (ULT). The constructed method of failure modes on the shallow ULT are proposed, together with the failure mode for the shallow unsymmetrically load single tunnel, based on the basic assumptions and basic theories of limit analysis method (LAM).

The probable route sets in the network diagram were calculated by adjacency matrix method, and based on the assumption that activity becoming the key obeyed 0-1 distribution, a probable route matrix was established. A random variable matrix was structed by monte carlo simulation under condition of activity time independent distribution. A matrix algorithm model was built by isolating activity times impact on activity becoming the key for the first time. This model with a simple and optimal algorithm avoided the computation complexity of network planning time parameter, to evaluate project duration risk rapidly and statistical analyze the probability of activity becoming the key and the influence degree of activity time fluctuation impacting on project duration, providing theoretical and data support for decisions. Empirical research on a tunnel engineering project verified its practicability and feasibility, providing a new powerful tool for assessing project duration risk in the network diagram quickly.