路牙石裂纹出现的原因。
The reason of the crack of the road stone.
气温变化时，自然界物质就会出现热胀冷缩，水的物理特性则不同。水密度在4℃时最高，水分子独立而且自由流动。当从4℃降至0℃（冰点）时，就会结冰，冰中分子呈现立体三维状，排反序列式样，这样子的布局易留下较多“空缝隙”，密度会降低。试验证明，水结冰后，体积增加0.11倍。即将结冰时，水进入路牙石孔缝后遇冷结冰，体积变大，会膨胀路牙石中的微细孔，路牙石会吸到更多的水进微孔中，细缝隙被胀大，反复循环，使路牙石的膨胀裂纹。
When the temperature changes, the natural materials will expand and contract, and the physical characteristics of water are different. Water density is the highest at 4 ℃, and water molecules flow independently and freely. When the temperature drops from 4 ℃ to 0 ℃ (freezing point), the ice will be frozen. The molecules in the ice will be three-dimensional and in reverse sequence. In this way, more "empty gaps" will be left and the density will be reduced. The experiment shows that the volume of water increases 0.11 times after freezing. When it is about to freeze, when the water enters into the crack of the curbstone, it will freeze when it is cold, and the volume will increase, which will expand the micro hole in the curbstone. The curbstone will absorb more water into the micro hole, and the micro hole will be expanded, and the circulation will be repeated, which will make the expansion crack of the curbstone.