The bridge near a school in Zhaoqing collapsed naturally. What is the cause of the collapse?

Collapse refers to natural phenomena such as buildings, mountains, roads and mines, which collapse and fall under the non-human action of natural forces. Due to poor stratum structure, rain erosion or construction defects, steep slopes near roads and dams, or sudden collapse of tunnels and tunnel tops, most of them belong to accidents. One is geotechnical. Rock and soil are the material conditions for collapse. Because of the different types of collapse, the scale of collapse is also different. Usually, there are all kinds of magmatic rocks (also known as igneous rocks), carbonate rocks (also known as water rocks), metamorphic rocks (also known as primary rocks), sandstone, glutenite (also known as primary rock loess), loess with compact structure, shale, marl and other interbedded rocks and loose soil layers. These rock collapses are usually dominated by falling and spalling.

The cutting and separation of different structural planes, such as geological structural joints, fractures, bedding planes and faults, provide boundary conditions for the formation of collapse from slopes (mountains). The more cracks on the slope, the more likely it is to collapse. The steep structural plane is approximately parallel to the extension direction of the slope, which is most conducive to the formation of slope collapse. Topography Riverside, riverside, lakeside, ditch side, various slopes, slopes of railways and highways, slopes under construction and various artificial slopes are all landforms that are prone to collapse. High and steep slopes with a slope greater than 45 degrees, isolated mountain passes or groove slopes are all favorable landforms that are easy to collapse. Rock and soil type, geological structure and landform are the basic conditions for the formation of collapse, which are generally called geological conditions.

Earthquake. The earthquake caused the slope to shake, destroyed the slope balance, and then induced the slope to collapse. Generally, earthquakes with intensity greater than 7 degrees will induce a large number of collapses. Snow melting and rainfall, especially heavy rain, heavy rain and long-term continuous rainfall, make surface water penetrate into the slope, soften the rock and soil and its weak surface, generate pore water pressure and induce collapse. Surface erosion, river immersion and other surface water bodies constantly scour the edges and feet, which will also induce collapse. Unreasonable human activities, such as excavation at the foot of the slope, underground mined-out areas, reservoir water storage, water discharge and other human activities that change the original equilibrium state of the slope, will induce collapse activities. There are also some other factors, such as frost heaving, day and night temperature changes and so on. This will also lead to collapse.

Before the collapse, there are usually some precursors: cracks appear behind the collapse; The front edge of the landslide falls, the soil rolls down, and small landslides and small landslides continue to occur; There is new collapse deformation on the slope, and even a small area of earth and stone spalling; There are occasional sounds of tearing, rubbing and squeezing in the lithologic collapse. When you see the omen, you must pay attention to the following points: don't take any chances, not at all? Maybe the collapse wouldn't have happened? This idea; It is necessary to evacuate in time and notify the surrounding residents and tourists. When the collapse is about to happen or is happening, evacuate the personnel first, do not dump the soil and clean the ditches immediately, and move immediately after the disaster situation stabilizes; After the rainstorm, although the weather turns fine, the collapse disaster may still occur within 5-7 days. So after the evacuation, although there was no collapse, as long as the weather cleared up, we had to move back home.