Monitoring of pipe jacking crossing Suichuan River in the 2nd West-to-East Gas Pipeline

This paper describes the construction technology and principle of pipe jacking in crossing Suichuan River in the 2nd West-to-East Gas Pipeline. The optimal surface settlement monitoring program is selected in accordance with actual geological conditions. Monitoring measurement values indicate that the mass displacement change of surface soil after pipe jacking is related to the distance between pipe pusher and monitoring point, and the monitoring point near the axis is much larger than surrounding monitoring points in the settlementchange. In four stages of displacement change, the displacement in the second stage is largest. After the pipe pusher passes through the monitoring point, stress relaxation causes reduction of soil pressure, which results in rapid settlement of the ground. In the pipe jacking construction, overlying soils is first uplifted and then settled to gradually reach a fixed value under normal work condition. Settling volume caused by the jacking in different stages is calculated and the calculation data is in a small difference to measured data, which shows that themonitoring data can be taken as the basis in evaluating pipe jacking construction safety conditions.