Two-Layer Base Seal for Salt Stockpile Deformation
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Solution Overview
Problem
Existing base sealing technologies for tailings salt heaps, such as clay sealing and mixed mineral layers, struggle to maintain effectiveness under high mechanical stresses and deformations without significant deterioration in permeability coefficient, necessitating an alternative that can absorb substrate and base seal deformations while maintaining stability.
Innovation Solution
A two-layer base sealing system comprising an upper layer of gravel, sand, and bentonite or powdered clay with a permeability coefficient ≤10^-9 m/s, and a lower layer of sand and bentonite or powdered clay with a permeability coefficient ≤5*10^-10 m/s, optionally including a polymer, allowing for self-regeneration during deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer base seal is used, then the structure is simple, but it cannot maintain constant permeability under deformation
Solution Approach 1:
The base seal is divided into two distinct layers: an upper layer with higher permeability (k ≤ 10^-9 m/s) containing gravel and sand, and a lower layer with lower permeability (k ≤ 10^-10 m/s) containing finer sand and bentonite. This segmentation allows each layer to perform different functions during deformation, with the upper layer providing structural stability and the lower layer maintaining sealing effectiveness, thereby resolving the contradiction between structural simplicity and permeability stability.
Solution Approach 2:
The base seal uses composite materials combining different grain sizes and permeability characteristics. The upper layer comprises gravel (8-16 mm), sand (0-2 mm), and bentonite (2-10% by weight), while the lower layer comprises sand (0-2 mm), bentonite (≥11% by weight), and optionally polymer. This composite structure enables the system to maintain constant permeability under deformation by allowing material interaction between layers.
2Strength
If the base seal is made rigid to withstand high loads, then strength is improved, but deformability is reduced
Solution Approach 1:
Different regions of the base seal have different mechanical properties tailored to their specific functions. The upper layer has higher friction angle (φ≥35°) and greater deformability to absorb settlements, while the lower layer has lower friction angle (φ≥30°) and provides structural support. This local differentiation allows the overall system to both bear high loads and absorb deformations effectively.
Solution Approach 2:
The base seal system is designed to dynamically adapt to deformation conditions. During settlement, the upper layer deforms more than the lower layer, creating voids that are subsequently filled by material migration from the lower layer. This dynamic response allows the system to maintain its sealing function throughout the deformation process, transforming from a static structure to a dynamically adaptive system.
3Reliability
If bentonite content is increased to reduce permeability, then sealing effectiveness is improved, but salt resistance deteriorates
Solution Approach 1:
The invention optimizes the bentonite content parameter within specific ranges: 2-10% by weight in the upper layer and ≥11% by weight in the lower layer. Additionally, when polymer is added to the lower layer, it increases salt resistance while maintaining the reduced permeability achieved by the bentonite. This parameter optimization resolves the contradiction by finding the optimal bentonite concentration that provides sufficient sealing while minimizing salt solubility effects.
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 two-layer system maintains constant permeability and enhances salt resistance, ensuring the base seal's effectiveness and stability under load-induced deformations by allowing the lower, more ductile layer to penetrate into the upper layer, thereby regenerating the seal and maintaining performance.
Implementation Method 1
If such a deformation occurs, it has been found that when the base seal is stretched, the lower layer penetrates into the upper layer, and there in turn ensures that the base seal continues to fulfill its function.
Data Source
AI summary
The invention relates to a base seal for a stockpile, in particular for a residual salt stockpile, said seal comprising two layers laid on top of one another. The upper layer has a mixture of gravel, sand and bentonite or powdered clay with a permeability coefficient of k = 10-9 m/s and the lower layer has a mixture of sand and bentonite or powdered clay with a permeability coefficient of k = 5*10-10 m/s.