Helical Knurled Calender Roll for Geomembrane Liner Stability
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Solution Overview
Problem
Existing geomembrane liners used in landfills face challenges in maintaining interfacial shear strength, especially on steeply sloped surfaces, due to potential slipping caused by gravitational forces, freezing/thawing cycles, seismic movements, and construction activities.
Innovation Solution
A knurled calender roll with a helical pattern of recesses is used to produce a geomembrane liner, where the recesses are formed by a knurling tool with conical spikes, creating conical projections on the liner surface that enhance ground gripping effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rectangular pattern of projections is used on the geomembrane, then the manufacturing process is simple and consistent, but the interfacial shear strength is reduced because subsequent projections follow pathways created by previous movements
Solution Approach 1:
The patent applies asymmetry by transitioning from a symmetric rectangular pattern to an asymmetric random pattern of projections. The random pattern ensures that no two projections are aligned in regular intervals, preventing the formation of continuous pathways that would reduce friction. This asymmetric distribution maintains manufacturing feasibility while significantly improving interfacial shear strength and preventing liner slippage.
Solution Approach 2:
The patent introduces variability in the vertical dimension by creating projections of varying heights rather than uniform heights. This dimensional variation disrupts the formation of continuous sliding pathways and enhances the mechanical interlocking between the geomembrane and the underlying surface, thereby improving interfacial shear strength without compromising manufacturing capabilities.
2Volume of stationary object
If deeper concavities with steeply sloped sides are used for waste storage, then additional landfill volume is achieved, but the risk of liner slipping increases due to greater gravitational forces
Solution Approach 1:
The patent employs conical projections with curved surfaces rather than sharp angular features. The conical shape provides optimized stress distribution and enhances mechanical interlocking with the underlying surface. The curved surfaces of the conical projections better conform to irregular substrates, improving grip and preventing slippage on steeply sloped landfill surfaces while enabling deeper concavity designs.
Solution Approach 2:
The patent creates a composite surface structure by forming conical projections from geomembrane material that integrates with the underlying compacted clay or geosynthetic clay liner. This composite interface combines the flexibility of the geomembrane with the shear strength of the underlying material, enhancing overall liner stability in deep, steep-sided landfills.
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 helical pattern of conical projections on the geomembrane liner provides enhanced interfacial shear strength, preventing sliding movements and ensuring secure retention on steep slopes, thus addressing the issue of liner slipping.
Implementation Method 1
The outer cylindrical surface of the calender roll is provided with surface discontinuities formed in a helical pattern
Implementation Method 2
The recesses are formed by a knurling tool with conical spikes, creating conical projections on the liner surface
Implementation Method 3
The helical pattern of conical projections on the geomembrane liner provides enhanced interfacial shear strength, preventing sliding movements
Data Source
AI summary
An apparatus is provided for forming recesses in a calender roll. The apparatus includes a rotational drive for rotating the calender roll around a rotational axis. The apparatus further includes a knurling wheel with knurling spikes projecting there from. The knurling wheel is rotatable about an axis that is aligned an acute angle to a plane that contains the rotational axis of the calender roll so that the knurling spikes produce a helical array of recesses in the outer surface of the calender roll. The calender roll then can be used to form a landfill liner with projections that are offset from one another to avoid having the projections form grooves and thereby preventing slippage of the landfill liner.