Two-Stage Goaf Grouting for Coal Pillar Protection
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Solution Overview
Problem
Existing grout injection methods for goaf repair neglect the impact on surrounding coal pillars, leading to damage and significant slurry loss, and fail to effectively prevent water inrush hazards during coal mining.
Innovation Solution
A method involving two-stage grouting operations: a first operation forming a barrier wall near the coal seam using low-pressure grouting to protect the coal pillar, followed by a second operation from outside to inside using high-pressure grouting to seal fissures and retain water, minimizing slurry loss and ensuring safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-pressure grouting is performed directly in the goaf, then grouting effectiveness is improved, but coal pillar damage occurs and slurry loss increases
Solution Approach 1:
The patent applies preliminary action by first forming a barrier wall at the boundary between the goaf and coal seam before performing the main grouting operation. This preliminary barrier wall prevents direct high-pressure grouting from damaging the coal pillar while still allowing effective sealing of the goaf. The barrier wall acts as a protective intermediate structure that enables subsequent high-pressure grouting without harmful effects.
Solution Approach 2:
The grouting process is segmented into two distinct stages: first forming a barrier wall at the boundary, then performing the main grouting operation from outside to inside. This segmentation allows the harmful effects to be isolated to a controlled area while protecting the coal pillar. The two-stage approach divides the complex grouting task into manageable phases with different pressure levels and objectives.
2Ease of operation
If grouting is performed without forming a barrier wall, then operation simplicity is maintained, but slurry loss increases significantly
Solution Approach 1:
The barrier wall formation is performed as a preliminary action before the main grouting operation. While this adds an initial step, it significantly reduces slurry loss during the subsequent grouting by preventing uncontrolled leakage. The preliminary barrier wall creates a contained environment that directs slurry where it is needed, reducing waste.
3Object-affected harmful factors
If barrier wall formation is added before grouting, then coal pillar protection is improved, but process complexity increases
Solution Approach 1:
The grouting process is divided into two sequential stages: barrier wall formation and main grouting operation. This segmentation allows each stage to be optimized independently - the barrier wall stage uses lower pressure for protection, while the main grouting stage uses high pressure for effectiveness. The clear separation of functions reduces overall complexity despite the additional step.
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 method effectively seals post-mining fissures, reduces maintenance costs, and minimizes water loss while protecting coal pillars, enhancing safety and resource conservation.
Implementation Method 1
performing the first grouting operation according to the first grouting pattern to form the barrier wall, including: controlling, at a ground area corresponding to a starting point of each of the first trajectory lines of the first grouting pattern, a drilling device to perform vertical drilling based on a vertical drilling parameter to obtain a plurality of first grouting holes; for each of the plurality of first grouting holes, controlling the drilling device to perform horizontal drilling along a first trajectory line corresponding to the first grouting hole based on a horizontal drilling parameter to obtain a plurality of first branch holes; controlling a plurality of low-pressure grouting pumps to perform the first grouting operation on each of the plurality of first branch holes based on a first grouting pressure to form the barrier wall
Data Source
AI summary
Provided are a method for grout injection repair and water retention in a goaf, including: determining extraction information on the goaf and a coal seam, forming a barrier wall through performing a first grouting operation at a side of the goaf near the coal seam based on the extraction information, performing a second grouting operation to complete a grout injection repair from outside to inside in the goaf based on the extraction information. The first grouting pressure of the first grouting operation is less than the second grouting pressure of the second grouting operation.