Reciprocating Rock Fracture Test Device for Triaxial Stress Simulation
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Solution Overview
Problem
Existing rock direct-shear apparatuses fail to accurately simulate the triaxial crustal stress state of deep rock formations and cannot simultaneously measure the friction characteristics and permeability evolution of rock fractures under crustal stress, leading to inaccurate measurements and inability to characterize mechanical and hydraulic properties of rock fractures.
Innovation Solution
A reciprocating rock fracture friction-seepage characteristic test device and method that includes an X-axis shear system, Y-axis and Z-axis stress loading systems, a servo oil source system, and a pore pressure loading system, allowing for simultaneous measurement of friction coefficient, stability parameter, and permeability of rock fractures under controlled stress conditions, using a rock specimen with sealing rubber layers to ensure accurate contact and prevent fluid leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a direct-shear mode is used to measure friction coefficient of rock fractures, then the measurement process is simple, but stress concentration caused by the load cell prevents complete contact between fracture surfaces resulting in inaccurate measurements
Solution Approach 1:
The patent divides the loading function into two independent systems: the load cell system for applying normal stress and the shear loading system for applying shear force. This segmentation eliminates the stress concentration problem by separating the functions, allowing accurate measurement of friction coefficients without the interference of stress concentration at the load cell contact point.
Solution Approach 2:
The patent introduces a rigid connection structure as an intermediary between the load cell and the fracture surfaces. This rigid connection ensures uniform distribution of normal stress across the fracture surfaces while maintaining complete contact, thereby eliminating the stress concentration effect and enabling accurate friction coefficient measurements.
2Device complexity
If an existing rock direct-shear apparatus is used, then the device structure is simple, but it cannot simulate the triaxial crustal stress state of deep rock formations
Solution Approach 1:
The patent designs a multi-functional testing apparatus that can simultaneously simulate triaxial stress states and measure both friction characteristics and permeability evolution. The device integrates normal loading, shear loading, pore pressure control, and permeability measurement functions into a single system, making it adaptable to deep rock formation conditions while maintaining reasonable structural complexity.
Solution Approach 2:
The patent transitions from a simple uniaxial or biaxial testing setup to a full triaxial stress state simulation by adding the third stress dimension (confining pressure). The apparatus applies independent normal stress, shear stress, and confining pressure to replicate the complex three-dimensional stress environment of deep rock formations, thereby achieving realistic simulation capability.
3Ease of operation
If existing test devices are used, then the measurement process is straightforward, but they cannot simultaneously measure friction characteristics and fracture permeability evolution
Solution Approach 1:
The patent merges the friction measurement system and the permeability measurement system into a single integrated testing apparatus. Both measurement functions operate simultaneously during the same shear loading process, eliminating the need for separate tests and providing comprehensive characterization of rock fracture mechanical and hydraulic properties in one experiment.
Solution Approach 2:
The testing apparatus is designed with multi-functionality to perform both friction coefficient measurement and permeability evolution measurement concurrently. The device includes integrated sensors and measurement systems that can detect mechanical deformation and fluid flow characteristics simultaneously, thereby achieving efficient multi-parameter characterization.
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
Enables efficient and accurate measurement of friction-seepage characteristics of rock fractures, effectively characterizing mechanical and hydraulic properties, and preventing unstable seismic sliding in reservoirs or cap rocks during operations like water injection, with a simple and stable device structure.
Implementation Method 1
an X-axis left hydraulic cylinder, an X-axis right hydraulic cylinder... The servo oil source system supplies oil to the X-axis left hydraulic cylinder and the X-axis right hydraulic cylinder
Implementation Method 2
using a rock specimen with sealing rubber layers to ensure accurate contact and prevent fluid leakage
Implementation Method 3
efficiently and accurately measure the friction coefficient and the stability parameter and the permeability of the fracture surface in the sliding process
Data Source
AI summary
The present disclosure discloses a reciprocating rock fracture friction-seepage characteristic test device and method. The test device includes an X-axis shear system, a Y-axis stress loading system, a Z-axis stress loading system, a servo oil source system, 5 a pore pressure loading system, and a host. The X-axis shear system includes an X-axis EDC controller, an upper shear box, a lower shear box, an X-axis left hydraulic cylinder, an X-axis right hydraulic cylinder, an X-axis left pressure head, an X-axis right pressure head, an X-axis left pressure sensor, an X-axis right pressure sensor, an X-axis displacement sensor, and an X-axis 10 displacement sensor. The pore pressure loading system includes an air cylinder, a pressure gauge, a pressure reducing valve, a fluid inlet pipeline, a fluid outlet pipeline, and a flowmeter.