What caused the sudden collapse of a residential area in Changsha?

The parking lot in the Oriental Pearl Community in Wangcheng District of Changsha City collapsed and a white car was "pitted". Contact the crane for emergency handling of residential property. Fortunately, no one was injured, and a safety fence was set at the collapsed position to prevent the accident from happening again.

The control of subgrade filling is not strict. The Code for Construction of Highway Subgrade stipulates that under normal circumstances, materials that cannot be compacted to the specified density and form stable fill cannot be used for subgrade filling. If the wet soft foundation is not properly treated, the bearing capacity of the foundation should be found out before the subgrade is filled in soft soil area, and then the reasonable soft foundation treatment scheme and construction technology should be adopted.

The specific reason is that the earth and stone filling of subgrade is not dense, and the fillers of each layer of subgrade filling are not leveled by grader or other leveling machinery, or the leveling effect is not good. When the subgrade is filled with stone or earth-rock mixture, the diameter of the block stone is too large, which makes the compactness of the stone-filled embankment or the stone-filled mixture embankment fail to meet the requirements of the specification. The compaction standards at the junction of filling and excavation are inconsistent, some construction units fail to construct according to the specification requirements, and the subgrade compaction machinery is insufficient, which makes the compactness of subgrade soil low, enhances the permeability of soil, softens subgrade soil and produces uneven settlement.

The backfill density of the abutment back of the structure is insufficient. The most easily overlooked thing in the backfill of the abutment back is that although the middle fill meets the requirements, the edge of the abutment is impermeable and has not been replaced. Therefore, there is water seeping into the pavement at the abutment back, which will affect the stability of the subgrade and cause the abutment back to sink over time.

Cracks in the garage It is reported that the underground garage in this community is below the collapsed area. The reporter noticed that cracks also appeared on the top of the garage. In response to the concerns and questions of the community owners, the reporter found the community developer. In this regard, the developer responded that the central landscape area is designed with a cavity layer, and the cavity layer is covered with soil. The preliminary judgment is that the cavity layer in the landscape area is cracked, which leads to ground subsidence and has no effect on residential buildings.

"When we designed it, we actually considered the problem of this load. In fact, greening and soil covering are considered. It's just that this situation is not what we expected. Our initial judgment may be that my hollow roof is cracked, but the specific reasons need further investigation. "

Natural disaster ground collapse refers to the geological phenomenon that the surface rocks and soil fall downward under the action of natural or man-made factors, and the ground forms collapse pits (holes). When this phenomenon occurs in areas with human activities, it may become a geological disaster.

Ground collapse or settlement is another form of vertical ground deformation and destruction under natural conditions. Karst ground collapse refers to the ground deformation and damage caused by loose earth and stone covered on soluble rock strata developed in karst caves under the action of external dynamic factors, and its main manifestation is site collapse, and most wells are cone-shaped collapse pits. It is a kind of ground collapse or subsidence. Karst collapse is generally small in scale and slow in development, and will not have a sudden impact on human life.