Fly Ash Cementitious Base Layer for Coal Gangue Filling
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Solution Overview
Problem
Current filling technologies for open pits and gullies using coal gangue and fly ash are inadequate due to permeability issues, leading to groundwater pollution and instability, and existing geomembranes are expensive and prone to damage.
Innovation Solution
A method involving a double-impermeable base layer of fly ash-based cementitious material with a polymer waterproof coating, followed by three-dimensional layered filling with coal gangue and fly ash, providing a compact, oxygen-insulating, and flame-retardant structure that immobilizes harmful substances through geo-aggregation reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a geomembrane is laid to prevent leachate migration, then pollution prevention is improved, but cost increases and mechanical strength is limited making it prone to damage
Solution Approach 1:
The patent employs a composite filling structure combining multiple materials: fly ash-based cementitious material forms the base layer, polymer waterproof coating provides impermeability, and overlying fill materials create a multi-layer composite system. This composite approach replaces the single geomembrane solution with a more robust, multi-functional material system that provides both pollution prevention and structural stability.
Solution Approach 2:
The patent changes the physical and chemical parameters of the filling materials by using fly ash-based cementitious materials that undergo hydration reactions to form impermeable structures. The polymer waterproof coating modifies the surface properties to achieve low permeability. These parameter changes create a durable, damage-resistant alternative to fragile geomembranes.
2Productivity
If coal gangue is directly used as filler, then filling efficiency is improved, but heavy metal pollution of groundwater and soil occurs
Solution Approach 1:
The patent introduces fly ash-based cementitious material as an intermediary layer between the coal gangue and the environment. This intermediary material binds heavy metals through adsorption and chemical reactions, preventing their direct contact with groundwater while maintaining the filling function. The cementitious material acts as a barrier and stabilization medium.
Solution Approach 2:
The patent converts potentially harmful coal gangue and fly ash waste materials into beneficial filling materials. Through proper mixing and curing, these waste materials form a stable, impermeable structure that immobilizes heavy metals and provides structural support, transforming environmental hazards into constructive elements.
3Strength
If fly ash with high free CaO and SO3 is used, then self-hardening properties are improved, but late expansion and poor stability occur
Solution Approach 1:
The patent carefully controls the chemical composition parameters of the fly ash-based cementitious material, optimizing the ratios of fly ash, cement, and water. By adjusting these parameters, the patent achieves adequate self-hardening while minimizing excessive expansion. The water-to-cement ratio and curing conditions are optimized to balance strength development with dimensional stability.
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 prevents leachate migration and pollution, ensuring environmental safety and reducing costs by forming a durable, impermeable barrier that stabilizes the filling material and immobilizes harmful substances.
Implementation Method 1
spraying a layer of polymer waterproof coating on a surface of the fly ash-based cementitious material
Implementation Method 2
the free Ca2+ in the fly ash promotes the formation of a hydrated cementitious product to coat the surface of the coal gangue
Implementation Method 3
the free Ca2+ in the fly ash promotes the formation of a hydrated cementitious product to coat the surface of the coal gangue, which has an oxygen-insulating and flame-retardant effect
Implementation Method 4
The fly ash-based cementitious material at the bottom of the pit forms a hard protective shell with a dense internal structure
Implementation Method 5
Such a double-impermeable structure has a small permeability coefficient, and can effectively block the migration of leachate
Data Source
AI summary
A method for ecological filling with mixed coal gangue and fly ash includes the following steps: S1: construction of a double-impermeable base layer: leveling a pit or gully, laying a fly ash-based cementitious material, compacting and curing; spraying a layer of polymer waterproof coating on a surface of the fly ash-based cementitious material, and fully curing to obtain a double-impermeable protective structure; S2: three-dimensional layered filling: dumping coal gangue and fly ash in sequence on the double-impermeable protective structure formed in S1, where the coal gangue and the fly ash are three-dimensionally layered and well graded; the coal gangue is coal gangue after coal washing, which is used as an aggregate; the fly ash is used as a filler and cementitious material to achieve a compact filling structure; and S3: rolling: rolling by a roller after the three-dimensional layered filling.