1、 The core cause of arching problem
Arching is manifested as an upward bulge in the middle area of the site, which feels hollow and floating when stepped on, and in severe cases, adjacent plates form a "human" shaped bend.
1. No release of thermal expansion and contraction stress (common cause, accounting for over 80%)
Mechanism: The linear expansion coefficient of polypropylene is about 8-12 × 10 ⁻⁵/℃. A 20 meter long basketball court, if installed at a temperature of 10 ℃ and the surface temperature rises to 50 ℃ in summer, can theoretically extend up to 20 × 1000 × (40) × 10 × 10 ⁻⁵=8mm. If no expansion joints are reserved around or filled in, the 8mm extension cannot be released and can only be compressed towards the middle, causing arching.
Typical features: appearing during high temperatures in summer, disappearing or decreasing in winter; The arch position is usually at the center of the site rather than the edge.
Direct inducement: During installation, the walls around the perimeter are blocked, cement mortar falls into the expansion joints, and the edge strips are fixed with rigid materials without any sliding allowance.
2. Failure to release internal stress during installation
Mechanism: Long term stacking of flooring in packaging boxes can cause slight warping (memory deformation). If the package is unpacked and installed directly without sufficient spreading and relaxation, the residual stress inside will gradually release during use, leading to local arching.
Typical feature: It gradually appears within one week to one month after installation, with a non seasonal pattern.
Direct inducement: The interval between taking out the packaging box and completing the installation is less than 2 hours; During installation, the rubber hammer was not used to evenly strike and release stress.
3. Foundation ground bulging or expansion
Mechanism: The rusting, frost heave, or salt alkali crystallization of the steel bars inside the concrete foundation causes the floor to rise from below.
Typical features: The arch position is fixed, and after removing the floor, obvious protrusions or bulges can be seen on the foundation ground.
Direct cause: Poor quality of foundation construction, lack of moisture-proof (based on actual reports) isolation layer, or use of damp slag filling.
4. Defects in lock buckle design lead to stress concentration
Mechanism: The lock buckle of poor quality flooring is rigidly connected (without sliding clearance), or the lock buckle is too tightly engaged. During thermal expansion, adjacent plates cannot move slightly relative to each other, and stress is concentrated at the root of the lock buckle. When it accumulates to a certain degree, either the lock buckle fractures or the plate buckles upward and arches.
Typical feature: The arching area is accompanied by the fracture of the locking buckle (after removal, it can be found that the root of the male buckle is white or broken).
Direct cause: Lock clearance
2、 The core reason for the curled edge problem
The raised edge is manifested as the edge of the field (especially the corners and middle of the long side) lifting upwards, and the edge shaking up and down when stepping on it, separating from the base ground.
1. Failure of edge fixation (common reasons)
Mechanism: Only one side of the edge floor is connected by a locking buckle, and the other side is pressed down by a trimming strip. When the spacing between the expansion bolts of the edge strip is too large (>50cm), the bolts become loose, or the stiffness of the edge strip is insufficient, the edge floor will protrude outward during thermal expansion, but cannot retract after cooling. When pulled back by the locking buckle, an upward force is generated, resulting in edge warping.
Typical features: The lifting height decreases from the edge to the inside of the field; After pressing with your hands, it can temporarily adhere and rebound after releasing.
Direct inducement: The edge strip is only glued without being fixed with bolts; Expansion bolts are installed on loose mortar layers; The thickness of the edge strip is less than 2mm, and the stiffness is insufficient.
2. Foundation edge sinking or deformation
Mechanism: Local subsidence occurs at the edge of the foundation ground due to uneven stress (such as vehicle rolling on the edge) or settlement of backfill soil. When the floor crosses the settlement boundary, it forms a suspended structure, and the edge loses support and tilts upwards.
Typical features: curled edges accompanied by obvious gaps below the floor (fingers can be inserted); Cracks or sinking marks can be seen at the edge of the foundation.
Direct cause: The edge of the concrete floor has not been reinforced; There is no retaining beam set at the edge of the outdoor site.
3. Reverse drainage slope leads to water accumulation and soaking
Mechanism: If the foundation slope at the edge of an outdoor site is reversed (i.e. the edge is low and the center is high), rainwater will accumulate under the edge floor. Long term soaking causes the foundation to soften or freeze, and the edges of the floor are lifted by ice crystals.
Typical features: Water stains, mold spots, or peeling off of the base surface can be seen in the curled edge area at the same time; Winter is particularly severe.
Direct cause: basic slope less than 0.3% or occurrence of reverse slope; The drainage ditch is blocked.
4. Uneven stress release at cutting edges
Mechanism: The cut edge plate loses its original locking constraint, and the thermal stress (if thermal cutting is used) or microcracks generated by cutting can cause the plate to warp. If the cutting width is less than one-third of the width of the entire board, the rigidity of the narrow strip board is not sufficient to resist its own bending stress, and it will inevitably warp.
Typical features: Edge curling occurs on narrow strips after cutting (width
Direct cause: typographical calculation error, resulting in the subsequent row being cut too narrow; Cutting with an angle grinder produces local overheating deformation.
3、 The interaction between arching and curling edges
Arching and curling often do not occur in isolation. Typical chain reaction: During high temperatures in summer, the central part of the site arches, pushing the entire floor to both sides → The edge floor bears a huge horizontal thrust → The edge strip is loosened or deformed → After cooling down in autumn, the floor shrinks back, but the edge strip is no longer effective and cannot be pressed down → The edge floor tilts upwards → In the following summer, the raised edge blocks the normal expansion of the floor, and stress concentrates at the raised edge, causing the lock buckle to break or the raised edge to intensify.
This cycle of "thermal expansion arching cold contraction curling edge" is a common aging mode in outdoor venues.
