Model Test of Joint Leakage Law in a Subsea Shield Tunnel

Project Category: Tunnel Leakage Monitoring Test

1. Project Overview

By the end of 2020, a total of 45 cities in mainland China had opened 244 urban rail transit lines, with the total operating mileage reaching 7,969.7 km. Shield tunnels are generally assembled from concrete segments. Under the action of water pressure in water-rich areas or beneath riverbeds, leakage incidents such as water seepage, sand loss, and mud leakage are prone to occur at the segment joints.

　　Figure 1 The ground section of the right tunnel in the Green Island Lake Huyong shield section of Foshan Metro Line 2 collapsed

2. Service Content

• This project requires providing calibration, remote data analysis, and processing services for pore pressure sensors and earth pressure sensors to the project party.

• The sensors provided for this project need to record real-time pore water pressure and earth pressure data of shield tunnels at different leak widths and leak positions under different water levels, in order to analyze the stress and deformation laws of the soil around the leak.

• The pore pressure sensor used in this project requires miniaturization (diameter ≤ 10mm) and resolution ≤ 0.020kPa (to record changes in pore water pressure within the soil); The earth pressure sensor requires miniaturization (diameter ≤ 12mm) and resolution ≤ 0.050kPa (to record changes in earth pressure inside the soil); Both the pore water pressure sensors and earth pressure sensors are required to have good long-term seawater corrosion resistance.

• This project requires all sensors to have a service life of 1 year, a failure rate of ≤ 5%, and a project operating condition duration of ≥ 90 days.

• The instrument models provided for this project are DSP-I pore pressure sensor (customized) and ESP-II earth pressure sensor, with the main parameters shown in Table 1.

3. Project Overview and Representative Data

(1) Experimental equipment

The experimental equipment used in this test is an underwater tunnel leakage visualization test device that can control the position and width of the leakage point[2].

 (2) Experimental representative data

4. Service evaluation

Highly praised by users: All DSP-I pore pressure sensors and ESP-II earth pressure sensors can work well in harsh environments that have been soaked in seawater for up to 3 months (average temperature ≥ 30 ℃), and DSP-I pore pressure sensors and ESP-II earth pressure sensors have the characteristics of good response accuracy, stability, and long service life, reaching the leading technical level of similar products in China.

 References:

[1] Investigation Report on the Major Accident of "2.7" Permeable Collapse in the Phase I Project of Foshan Metro Line 2 in Guangdong Province in 2018

[2] Lu Ping, Chen Can, Liao Chenchang, Zhang Youliang Model experimental study on the leakage law of underwater shield tunnel joints [J]. Journal of Rock Mechanics and Engineering, 2019,38 (05): 993-1004