What is the geographical environment of Qidong City?
Qidong City is adjacent to the North Branch of the Yangtze River Estuary in the south. The eastern section is bounded by the center of the river, and the western section Yonglongsha is connected with Chongming District of Shanghai. The national highway network G40 runs through Qidong, and the Chongqi Bridge It is connected to Chongming Island in Shanghai; it is bordered by the Yellow Sea to the east and north, and Haimen City to the west.
Qidong City belongs to the northern subtropical humid climate zone, with obvious maritime monsoon climate characteristics, four distinct seasons, sufficient sunlight, mild temperatures, abundant rainfall, a long frost-free period, changeable weather in spring, and cool and average weather in autumn. The air pressure is 1016.5 hPa, the annual average temperature is 15°C, the annual average precipitation is 1037.1mm, the average relative humidity is 81%, the annual average number of days above 35°C is 5 days, and the maximum number of days is 18 days (1964); the annual maximum wind direction is Southeast wind, the annual average wind speed is 3.5m/s; the annual average sunshine hours are 2073 hours; the annual average frost-free period is 222 days. Among them, Yuantuojiao in Yinyang Town is the first place in Jiangsu to see the sunrise.
The terrain within the territory is flat, with crisscrossing ditches and rivers, and it is a low-level coastal area. The topography of the micro domain is slightly undulating, slightly tilting from northwest to southeast. The inverted river is the natural dividing line between the north and south landforms. The elevation in Henan (Wusong elevation) is 3.6 to 4.6 meters, and the elevation in Hebei is 5.1 to 6.1 meters. The north-south slope is about 1/30000 meters. . The east-west slope is about 1/43500 meters. The annual groundwater level is 1.2 to 1.6 meters.
Within 17 meters under the natural ground, there are mainly: fill soil layer (or cultivated soil layer), its general thickness is 0.6 to 1.0 meters, and the soil quality is soft. The secondary layer is silty clay, and some areas are dominated by thin layers of silty clay with silt soil. The thickness of this layer ranges from 2 to 4 meters. It is a good supporting layer for the foundation of general buildings. The lower layer is composed of silt and clay. The soil layer is partially sandwiched with a thin layer of silt and fine sand, which is relatively uniform. From west to east, the main silt changes to silt-clay interbeds, and the thickness gradually thickens by about 7.5 to 10.0 meters. Its bearing capacity is high, and the soil layer It has a certain thickness and is distributed stably, and the lower layer is a silt-fine sand layer. In general, the foundation bearing capacity of Qidong is generally 10-13T/m2, and it is an alluvial plain that is adjacent to the river and the sea.
The Qidong crystalline basement is buried deeply, and its lithology is weak and flexible. It is difficult to meet the rock conditions for large earthquakes. Since the Cenozoic, depression has dominated and has shown large-scale subsidence. movement, forming basins and plains, with large stratigraphic plasticity and weak rupture and deformation. Due to the active faults since the Cenozoic, most of them are synsedimentary faults. Energy is easy to release but not easy to accumulate. There is obvious oscillation in the lifting and lowering operations, so this area is not prone to major earthquakes. .