The analytic hierarchy process (AHP) approach has been widely used in multicriteria decision making (MCDM). It is very difficult to meet the consistency requirement of a comparison matrix (CM) in AHP. The authors analyze the reasons for inconsistent CM in AHP and propose an improved AHP (IAHP) to improve CM consistency by using a sorting and ranking methodology. The results of comparing AHP with IAHP by MATLAB simulation show that IAHP is more suitable for solving MCDM problems when the number of elements or factors is 5 or more in MCDM. A case study is presented to illustrate the performance of IAHP when applied to risk identification during an open-cut subway construction. The application results show that IAHP is superior to AHP in terms of CM consistency, information extraction effectiveness, and convenience in practical implementation.

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Shield tunneling under rivers often requires monitoring riverbed deformations in near real-time. However, it is challenging to measure riverbed deformation with conventional survey techniques. This study introduces a comprehensive method that uses the Global Positioning System (GPS) of the USA and the BeiDou navigation satellite system (BeiDou) of China to monitor riverbed deformation during the construction of twin tunnels beneath the Hutuo River in Shijiazhuang, China. A semi-permanent GPS network with one base station outside the river and six rover stations within the river was established for conducting near real-time and long-term monitoring. The distances between the base and the rover antennas are within two kilometers. The network was continuously operating for eight months from April to December 2018. The method is comprised of three components: (1) Monitoring the stability of the base station using precise point positioning (PPP) method, a stable regional reference frame, and a seasonal ground deformation model; (2) monitoring the relative positions of rover stations using the carrier-phase double-difference (DD) positioning method in near real-time; and (3) detecting abrupt and gradual displacements at both base and rover stations using an automated change point detection algorithm. The method is able to detect abrupt positional-changes as minor as five millimeters in near real-time and gradual positional-changes at a couple of millimeters per day within a week. The method has the flexibility of concurrent processing different GPS and BeiDou data sessions (e.g., every 15 minutes, 30 minutes, one hour, one day) for diffident monitoring purposes. This study indicates that BeiDou observations can also achieve few-millimeter-accuracy for measuring displacements. Parallel processing GPS and BeiDou observations can improve the reliability of near real-time structural deformation monitoring and minimize false alerts. The method introduced in this article can be applied to other urban areas for near real-time and long-term structural health monitoring.

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