The Contractor excavated across the road, lay a water pipe, put back the soil and sealed the surface with bitumen pavement. After a while, the newly constructed pavement sank and then failed. Why?
The cause is quite obvious, the excavated materials were not put back in order and compacted. Road pavement comprises the founding soil, which in this case likely fill materials, then about 350mm thick of sub-base and base materials( 75mm to 38mm sized crushed rock materials), before sealing off with 100m thick asphalt pavement. Each layer has to be strictly compacted by mechanical Compactor from lower layer to upper layer. Thus if no compaction is done, the layers will be in loose conditions. Upon loading and water seepage, the soil/road materials will be compressed and reorientated and resulting less volume, thereby causing the pavement to sink and crack.
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