Underground Shield Docking Model Test Platform
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Solution Overview
Problem
Current underground shield docking technologies face challenges in simulating actual working conditions, particularly in studying the deformation and stress effects caused by frost heave and thaw settlement, due to limitations in model test designs and the inability to debug and operate systems within the model.
Innovation Solution
A large-scale underground shield docking model test platform is developed, allowing personnel to enter the model for debugging and operation of test systems. The platform includes a test soil tank, partition wall, shield docking model, and freezing system, enabling simulations of grouting reinforcement, freezing reinforcement, and freeze-thawing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the model tunnel is buried in the test chamber before freezing system installation, then the test chamber can be sealed and boundary conditions can be controlled, but personnel cannot enter the tunnel to debug and operate the freezing system or carry out pre-grouting reinforcement
Solution Approach 1:
The test chamber is divided into two independent chambers: a first test chamber for burying the model tunnel and a second test chamber for housing the freezing system. This segmentation allows personnel to access the freezing system for debugging and operation while the model tunnel remains buried in the first chamber, resolving the contradiction between boundary condition control and system accessibility.
Solution Approach 2:
A coupling mechanism is introduced as an intermediary between the first test chamber and the second test chamber. This coupling mechanism transmits the freezing force from the freezing system to the model tunnel, allowing personnel to operate the freezing system externally while still achieving the desired freezing effect on the buried model tunnel.
2Reliability
If the model tunnel is buried in the test chamber, then the test can simulate actual underground conditions, but the lateral and vertical boundary conditions differ from actual situation, making it difficult to simulate stress and deformation accurately
Solution Approach 1:
The first test chamber is designed with specific dimensional relationships where the width and length are both greater than twice the outer radius of the model tunnel. This creates appropriate boundary conditions in the lateral and vertical directions, allowing accurate simulation of stress and deformation characteristics while maintaining underground condition simulation.
3Device complexity
If the segment lining behind the shield tail is not considered in the model test, then the test setup is simpler, but it is impossible to explore the relative displacement between shield and segment lining or evaluate waterproof safety
Solution Approach 1:
The model segment lining is pre-installed behind the model shield tail in the first test chamber before the freezing test begins. This preliminary action ensures that the segment lining is in place to explore relative displacement and evaluate waterproof safety during the freezing process, while maintaining reasonable test setup complexity through standardized installation procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The platform allows for accurate exploration of deformation characteristics, stress safety, and stability of shield structures, as well as the coupling effects of grouting and freezing reinforcement, providing reliable research solutions and feasible suggestions for optimizing strata reinforcement schemes.
Implementation Method 1
freezing is mainly employed for reinforcement in water-rich soft strata
Implementation Method 2
the impact of frost heave load on the stability of the shield structure during freezing reinforcement
Implementation Method 3
carry out pre-grouting reinforcement before freezing to study the coupling effect of grouting and freezing reinforcement
Data Source
AI summary
A large-scale underground shield docking model test platform and a test method using the same are provided. The test platform includes a test soil tank, a partition wall, a shield docking model, and a freezing system. The test soil tank is of an underground foundation pit structure, the partition wall is disposed in the test soil tank to separate the test soil tank into a filling area and a non-filling area. The shield docking model is disposed in the filling area and is a reduced-scale test model. The shield docking model is provided with the freezing system, including a refrigeration system, a coolant circulation system, and freezing pipes. The freezing pipes are arranged on the shield docking model and are connected to the refrigeration system through the coolant circulation system. The refrigeration system is placed on a laminate in the non-filling area of the test soil tank.