免费无码又爽又刺激高潮虎虎视频

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              Drainage function of curb stone

              May 01, 2019

              The upper layer of curbstone is made of ordinary concrete, and its impermeability can prevent the pavement rainwater from being poured into the pavement structure, and at the same time, the surface layer has a strong structural strength; the lower layer is made of porous concrete to form a water-permeable layer, which allows water in the pavement structure to pass through The permeable layer is smoothly discharged (usually the same cross section of the road, the road is higher than both sides, and the water inside the pavement structure flows to both sides under the action of gravity, and the porous concrete layer that enters the edge stone is discharged when it reaches the edge of the road).


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              免费无码又爽又刺激高潮虎虎视频
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