I have previously posted about leaning or tilting houses in Ho Chi Minh City here. There have been several recent Vietnamese news articles about houses adjacent to rivers collapsing, and there have been several stories lately about the collapse of large projects. The reasons for the collapse of large projects are always very complicated and in many cases never resolved. For houses, however, it is usually easy -- does the house have a strong enough foundation? And the houses that have collapsed into rivers usually suffered erosion of the river bank, undermining the house foundation.
There are many new townhouses and villas under construction in the urban infill area of Nhiêu Lộc south of Phan Xich Long Street along the Thị Nghè canal. This area used to be a wetlands area, as shown in this picture from 1972:
This condition is the norm for most areas of TP. Hồ Chí Minh away from the center of the city. The north side of the Phú Nhuận District and most of the Bình Thạnh District looked like this prior to 1975, even though these districts are close to the city center.
Nevertheless, strong foundations for houses are possible in these areas with short reinforced concrete piles, and almost all new townhouse or villas construction in HCMC feature these piles. Here is a video showing the shoving of these piles into the ground:
The hydraulic pile drivers used to shove these piles into the ground are relatively small and fit into the narrow four-meter wide lots typical in the urban areas of Saigon.
Once the piles have been driven, the foundation is excavated around the piles and the tops of the piles are cut off to the base of the foundation grade beams.
Pile tops are marked with yellow circles above. Notice how mucky the top layer of soil is.
