Tertiary Compression-Yielding Support for Large-Deformation Tunnels
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Solution Overview
Problem
Traditional tunnel support systems, including retractable steel arch frames, struggle with large deformations in fault fracture zones, leading to structural damage, high stress, and inadequate deformation resistance, especially in over-meter large deformation scenarios.
Innovation Solution
A tertiary cooperative compression yielding and energy-absorbing support mechanism comprising compression yielding and energy-absorbing anchor cables, a primary support compression yielding arch frame, and a secondary lining steel arch frame, with circumferential and radial compression yielding devices, providing multi-stage support and energy absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional rigid support systems (primary support layer and secondary lining layer) are used to resist large deformation of fracture zone surrounding rock, then the support system can provide sufficient stiffness and strength, but the primary support layer and secondary lining layer will be subjected to great formation pressure, causing concrete damage, steel arch distortion, and requiring support system replacement
Solution Approach 1:
The support system is divided into three independent layers: first layer (anchor cables with yielding devices), second layer (compression yielding arch frame), and third layer (secondary lining). Each layer independently bears and yields under pressure, distributing the formation pressure across multiple segments rather than concentrating it on a single rigid structure, thereby preventing concrete damage and steel arch distortion
Solution Approach 2:
The support system transitions from a rigid state to a yielding state through controlled parameter changes. The anchor cables and arch frames incorporate yielding devices that allow controlled deformation under formation pressure, changing the stiffness parameter dynamically. This enables the support to absorb energy through deformation while maintaining strength, avoiding the brittle failure mode of traditional rigid supports
2Stress or pressure
If retractable steel arch frame with spring compression is used to allow compression yielding and energy-absorbing, then the deformation pressure on the main structure is reduced, but when surrounding rock has large deformation, the spring stress exceeds its bearing limit, causing spring damage and complete failure
Solution Approach 1:
The compression resistance function is segmented across three layers: the first layer anchor cables provide initial compression resistance, the second layer arch frame provides intermediate compression resistance with yielding capability, and the third layer secondary lining provides final support. This segmentation ensures that no single spring or component bears the entire deformation pressure, preventing stress from exceeding bearing limits
Solution Approach 2:
The first layer anchor cables with yielding devices act as a preliminary cushion, absorbing initial deformation pressure and reducing the stress burden on the second layer arch frame springs. This prior cushioning prevents the springs from immediately experiencing excessive stress that would exceed their bearing capacity
3Loss of energy
If retractable steel arch frame relies on spring deformation for compression yielding, then energy absorption is achieved, but elastic stress always appears inside the steel arch frame after spring deformation, making the steel arch frame always in a high stress state, not conducive to long-term stable support
Solution Approach 1:
The yielding devices in the anchor cables and arch frame are designed to undergo irreversible plastic deformation, discarding the elastic energy that would otherwise remain as residual stress. By allowing controlled permanent deformation in the first and second layers, the system dissipates energy without leaving harmful residual stresses in the third layer secondary lining, enabling long-term stable support
4Device complexity
If a single retractable steel arch frame is used, then the structure is simple, but the resistance to deformation is weak and the deformation amount is small, making it difficult to play an effective support role in over-meter large deformation disaster
Solution Approach 1:
The support system is segmented into three functional layers with different deformation capacities. The first layer anchor cables accommodate small deformations, the second layer arch frame accommodates medium deformations through spring compression, and the third layer secondary lining provides final support. This segmentation enables the system to adapt to over-meter large deformations while maintaining structural integrity
Solution Approach 2:
The three support layers are nested within each other, with the first layer anchor cables embedded in the surrounding rock, the second layer arch frame positioned within the tunnel perimeter, and the third layer secondary lining forming the final tunnel lining. This nested arrangement allows each layer to contribute to deformation resistance while working cooperatively
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 mechanism effectively controls large deformations, maintains structural integrity, reduces damage risk, and enhances deformation resistance, ensuring stable support and reducing economic losses.
Implementation Method 1
the compression property of the spring is used to make the deformation pressure acting on the main structure of the steel arch frame not to be too large
Implementation Method 2
tertiary cooperative compression yielding and energy-absorbing support mechanism
Data Source
AI summary
A tertiary cooperative compression yielding and energy-absorbing support mechanism. The compression yielding and energy-absorbing anchor cables play a basic support role, and the circumferential compression yielding device can make the primary support compression yielding arch frame have a constant resistance deformation in the circumferential direction, while the primary support compression yielding arch frame and the secondary lining steel arch frame have a relative dislocation movement in the radial compression yielding device, and the tertiary compression yielding and energy-absorbing structures are cooperated with each other to adapt to the over-meter large deformation movement of the surrounding rock.