Self-Sealing Water Bag Pulse Fracturing for Hard Coal Roofs
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Solution Overview
Problem
Current technologies for hard roof fracturing in coal mines, such as drilling blasting and hydraulic fracturing, face challenges like high risk of gas explosion, dust diffusion, water consumption, and difficulty in sealing holes, while high-voltage electric pulse technology lacks mature industrial equipment and effective methods for underground applications, especially for thick roofs and directional fracturing.
Innovation Solution
A self-sealing water bag-based high-voltage electric-pulse fracturing device with multiple electrode structures, allowing for efficient rock breaking and stress regulation by using a portable self-sealing water bag and assembly rod to simplify hole sealing and enable multi-electrode synchronous discharge for layered fracturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If drilling blasting technology is used for hard roof fracturing, then rock breaking effect is improved, but risk of gas explosion and dust diffusion increases
Solution Approach 1:
The patent replaces the chemical blasting system with a high-voltage electric pulse system. Instead of using chemical explosives to fracture the hard roof, the invention uses electro-hydraulic effect where high-voltage electric pulses are discharged through water-filled sand bags to generate shock waves that break the rock. This substitution eliminates the harmful chemical reactions that cause gas explosion and dust diffusion while maintaining effective rock fracturing capability.
Solution Approach 2:
The patent introduces water-filled sand bags as an intermediary medium between the electric pulse source and the hard roof. The water in the sand bags serves as a conductor for the electric pulse and as a medium to generate and transmit shock waves to the rock, replacing the direct chemical explosion mechanism. This intermediary approach achieves rock fracturing without the harmful side effects of chemical blasting.
2Strength
If hydraulic fracturing technology is used for hard roof fracturing, then rock breaking is achieved, but equipment size is large and water consumption is high
Solution Approach 1:
The patent divides the water delivery system into multiple portable sand bags, each containing a small amount of water. Instead of using a large continuous water supply system, the invention segments the water into discrete portable units that can be individually positioned and discharged. This segmentation dramatically reduces total water consumption while maintaining fracturing effectiveness through concentrated electric pulse discharge in each bag.
Solution Approach 2:
The patent replaces the hydraulic pressure system with an electric pulse system. Instead of using high-pressure water jets to fracture the rock, the invention uses electro-hydraulic effect where electric pulses discharge through the water in sand bags to generate shock waves. This substitution eliminates the need for large water volumes and complex hydraulic equipment while achieving effective rock breaking.
3Strength
If hydraulic fracturing is used for hard roof fracturing, then rock breaking is achieved, but hole sealing under high pressure is difficult
Solution Approach 1:
The patent performs preliminary action by pre-filling sand bags with water and positioning them in the borehole before electric pulse discharge. The sand bags are prepared on the surface and then lowered into the hole, eliminating the need to seal the hole under high pressure. The portable nature of the sand bags allows them to be easily positioned and secured in place before the fracturing operation begins.
Solution Approach 2:
The patent uses sand bags as intermediary elements that simplify hole sealing. Instead of requiring the hole to be sealed against high water pressure, the sand bags serve as self-contained units that can be easily positioned and secured. The sand bag material and configuration provide natural sealing and retention, making the operation much easier than traditional hydraulic fracturing methods.
4Area of stationary object
If multiple electrode structures are used for thick roof fracturing, then fracturing coverage is improved, but device complexity increases
Solution Approach 1:
The patent segments the fracturing system into multiple identical sand bag units, each containing a simple electrode structure. Instead of using one complex electrode system, the invention uses multiple simple, standardized units that can be stacked or arranged to cover the required area. This segmentation simplifies each individual component while achieving extended coverage through replication.
Solution Approach 2:
The patent creates a universal sand bag unit that can serve multiple functions: containing water, holding the electrode structure, providing structural support, and enabling portable positioning. This multi-functional design allows the same basic unit to be used in various configurations for different fracturing requirements, reducing overall system complexity through standardization.
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 device facilitates safe, efficient, and cost-effective fracturing of hard roofs with reduced water usage, minimizing dust and gas risks, and allows for precise energy direction control, enhancing rock fragmentation and fracturing efficiency.
Implementation Method 1
A high-voltage electric pulse technology based on electro-hydraulic effect refers to charging a capacitor bank with a high-voltage direct-current power supply, and then discharging through an underwater electrode in a very short time, generating a pulse discharge in water, forming a plasma channel that penetrates the two electrodes and expands continuously, and at the same time generating a bubble pulsation phenomenon, and a shock wave is formed under a joint action of both.
Implementation Method 2
generating a pulse discharge in water, forming a plasma channel that penetrates the two electrodes and expands continuously, and at the same time generating a bubble pulsation phenomenon
Implementation Method 3
a shock wave is formed under a joint action of both. Because the water has characteristics of low compressibility, low deformation energy and low heat energy loss, a water shock wave propagating in the water may transfer energy to a surrounding rock almost without loss
Implementation Method 4
water and detonation gas seep into the fracture, and a splitting action of 'water wedge' makes a fracture expand and extend
Implementation Method 5
the water in a fracturing hole is atomized at a high temperature and a high pressure, absorbing gas and dust, playing a role of atomization and dust reduction
Data Source
AI summary
An electric-pulse fracturing device for hard roof of coal mine based on a self-sealing water bag and an using method thereof are provided. The device includes a power switch, a charging power supply, a current limiting protection resistor, an energy storage capacitor and a high-voltage electric pulse switch connected in sequence. The energy storage capacitor is connected with an end of a gas gap switch, an other end of the gas gap switch is connected with an assembled self-sealing water bag high-voltage electric pulse electrode structure through a high-voltage cable, and the electrode structure is fixed through an assembly rod. The self-sealing water bag high-voltage electric pulse electrode structure includes a self-sealing water bag and an electrode structure capable of focusing shock wave energy, and the number of the self-sealing water bag high-voltage electric pulse electrode structure depends on fracturing effect.