Research On The Impact Of Urban Metro Tunnel Construction On Existing Pipelines

Nowadays, urban rail transit construction has been launched on a large-scale among big cities in our country, involving numerous engineering problems, of which approaching existing underground pipelines is the most common one. Inadequate acknowledgement of pipelines or poor implementation of engineering measures will cause the metro construction to seriously affect the regular use of underground pipelines or even lead to material catastrophic consequences. With the engineering background that shaft’s horizontal adits approach the DN1200water supply pipelines in the Ling (Cuobuling Station)-Qing (Qingjiang Road Station) section of Qingdao Metro Line3, this thesis studies the regularity that how tunnel construction influence the pipelines from the following three aspects: pipeline diameter, burial depth of pipeline top and tunnel depth according to the characteristics of pipelines alongside Qingdao Metro Line3and Qingdao’s rock feature of "the upper layers being soft and the lower ones hard", and the conclusions and achievements are as follow:1. An incomplete statistics of pipelines alongside Qingdao Metro Line3shows that the pipeline research shall be conducted focusing on urban water supply pipelines whose burial depth is no longer than4m, pipe diameter within1000mm and with a flexible joint.2. Though the measured data on pipeline settlement, it’s concluded that the first, second and third step during the three-step excavation respectively cause44%,18%and16%of pipeline settlement; and inverse analysis of field measured DN1200water supply pipeline settlement is further performed to verify the reasonability of numerical simulation parameters and method.3. Taking the influence of pipeline diameter, burial depth of pipeline top and tunnel depth into account, numerical calculation model ANSYS is built to study the specific value of maximum ground settlement Smaxl and ground settlement trough width factor i (Smax1/i), maximum pipeline settlement (Smax2) and pipeline strain (με), and then to observe the influence regularity of these three elements on pipeline settlement.4. The differential settlement of ground and pipelines has been analysed, and thus draws the conclusion that it is acceptable for ground settlement to replace pipeline settlement when burial depth of pipeline top is no longer than2m.