Study on Geological Disasters and Environmental Geological Problems in Yantai City

Yantai, located in the east of Shandong Peninsula, is one of the important opening cities in China. The region has vast mountains, developed mining industry and rapid economic development. Under the influence of the development and evolution of geological environment and human activities, various environmental geological problems have emerged, resulting in geological disasters, especially mine geological disasters.

Regional geological disasters are divided into internal geological disasters, external geological disasters and geological disasters caused by human activities. The geological disasters caused by internal forces are mainly earthquakes, which are a natural phenomenon and an irresistible natural law that human beings can't control. Exogenous geological disasters mainly include gravity geological disasters, karst collapse geological disasters, ground deformation disasters caused by mining, marine erosion geological disasters and so on. Geological disasters caused by external forces, especially those related to human activities, can be prevented or even avoided. This paper mainly studies geological disasters caused by external forces.

First, the ground deformation disaster

1. Ground collapse

The ground collapse of mine goaf is the main type of ground collapse in Yantai, and karst collapse is only distributed in a small local area, which is less harmful.

(1) ground collapse of mine goaf

There are many subsidence points on the mined-out ground, which are distributed in almost all counties and cities (districts) according to the location of subsidence. The types of collapse are divided into gold mine, talc mine, coal mine, fluorite mine, building materials and other mine collapses.

(2) Geological disasters of karst collapse

Carbonate rocks are widely distributed in this area, mainly in Guangshan section of Jingshan Group, Dingguosi section, Zhanggezhuang Formation of Fenzishan Group and Xiangkuang Formation of Penglai Group.

2. Land subsidence

Yantai City is located in Jiaodong Peninsula, and its topography is mainly low hills with gentle ups and downs and gentle valley width and slope. There are continuous low mountains, gullies and plains, and depressions are distributed locally on both sides of the valley and coastal areas. No large-scale land subsidence disaster has been found, but due to the intensification of artificial mining activities, local and small-scale land subsidence is more developed.

3. Ground fissures

After investigation, there are four representative ground fissures in the city, namely, No.2 ground fissure in Linglong Mining Area, No.4 ground fissure in Linglong Mining Area, ground fissure in talc mine in Miaohou Township of Qixia City and ground fissure in Fushan Copper Mine.

The second is the disaster of slope environment variation.

Yantai is a gentle rolling hill with gentle valley width, gentle slope, high in the middle and low in the north and south. From west to east, there are Daze Mountain, Luoshan Mountain, Ai Shan Mountain, Yashan Mountain and Kunyu Mountain in the middle, forming a north-south trunk that runs across the east and west, with the highest elevation of 922m; The central mountainous area is generally 300 m ~ 800 m, accounting for 36.6% of the city's total area; The mountainous area and its extension are hilly areas with an altitude of 100m~300m ~ 300 m, accounting for about 39.7%. There are piedmont plains and coastal plains on the north and south sides, accounting for about 20.8%. Because mountainous and hilly areas account for 79.2%, the environmental variation disasters of slopes in this area are relatively developed, and the representative forms are collapse, landslide and debris flow.

Three. Coastal erosion disaster

Coastal erosion disasters in Yantai are mainly distributed in the west of Penglai and the north of Mu Ping.

Four. Sea (salty) water intrusion

Since the late 1970s, due to over-exploitation of groundwater in Yantai City, groundwater level funnels have been formed in coastal plains and river estuaries, resulting in seawater (salt water) invading and polluting groundwater. Since 1975, when seawater (salt water) invaded Laizhou city for the first time, seawater (salt water) pushed inland at the rate of 12% every year, which made the groundwater resources face a serious threat and the situation was very grim. Due to the invasion of seawater (salt water), the social and economic development of the city has suffered serious losses, the land is barren, the grain production is reduced, and it is difficult for people and animals to use water. Laizhou City has 12 towns, 126 natural villages and 270,000 mu of cultivated land. One village in Xiyou Town was invaded by seawater (salt water), the water quality deteriorated and the land was barren. At the same time, the sea (salty) water invasion also induced many other diseases, which greatly damaged people's health. In view of the great loss and harm brought by seawater intrusion to social and economic development and people's life, which has attracted great attention from all walks of life and the government, China Academy of Sciences, Yantai Water Conservancy Bureau and other units have conducted a large number of investigations on the present situation of seawater intrusion in our city.

According to the monitoring data for many years, by the end of 1999, the sea (salty) water intrusion area in Yantai City had reached 60 1.3 1km2, mainly distributed in the northern coastal area from Muping District in the east to Jiaolai River in Laizhou City in the west, with small areas in Laiyang City and Haiyang City in the south.

Five, the negative environmental impact of groundwater exploitation

With the vigorous development of national economy and the deepening of opening to the outside world, Yantai City is facing severe resource and environmental problems, among which the environmental effect of water resources development and utilization is the most obvious, which restricts the sustainable development of regional economy. In addition to the above-mentioned seawater intrusion disasters, the negative environmental effects of groundwater exploitation in Yantai City also include the following negative environmental effects:

1. Overexploitation of groundwater has formed a subsidence funnel.

Yantai city is located in the hilly and mountainous areas with poor water resources, and the main water supply sources are distributed in the valley alluvial-diluvial plain. In recent years, the city's rapid economic development and increasing demand for water for industrial and agricultural production have led to over-exploitation of various water sources, and the groundwater level has continued to decline, forming a concentrated distribution area of water level drop funnel.

2. Soil salinization

Soil salinization refers to the fact that the alkali content in the soil exceeds the level of cultivated soil, so that crops are harmed when they begin to grow. Salinization in Yantai city is distributed in the muddy coastal zone on the west and south coast of Bohai Bay. The reason of soil salinization is mainly caused by poor water management of irrigated land. The genetic type of soil salinization is coastal type. Coastal saline soil area is caused by seawater intrusion due to excessive pumping of groundwater, while inland saline soil area is caused by poor irrigation water management in the Yellow River Plain. For example, 1958, unilateral development of irrigation, large water diversion and storage, and inadequate drainage. The regional inflow greatly exceeds the drainage, which raises the soil groundwater level and causes the soil salinization to develop rapidly in 1959 ~ 196 1 year. In the late 1960 s, the climate was frequently dry, the soil groundwater level dropped, and the salinization area decreased. In 1970s and 1980s, due to years of drought, the secondary salinization area has quietly increased since the Yellow River Diversion resumed, due to the lack of control of water level and irrigation quantity, high-level water diversion, massive irrigation and neglect of drainage. Soil salinization seriously affects the development of regional agriculture.

3. Ground deformation caused by groundwater exploitation

The main forms of ground deformation are ground subsidence, ground fissure and ground collapse. Due to the expansion of groundwater funnel area, land subsidence occurred in some areas, which led to a series of environmental geological problems such as cracks in Daguhe dike, which brought hidden dangers to dike safety. Ground fissures are a kind of geological phenomenon that cracks are produced in the surface rock and soil under the action of natural or man-made factors, and cracks with a certain length and width are formed on the ground. The causes of ground fissures in Yantai city are related to the exploitation of groundwater. For example, the ground fissures in Fushan copper mine in Yantai are affected by mine drainage. 1In August, 986, a ground fissure occurred in the basketball court of Dongting Primary School in Fushan. Cracks spread to the northwest, more than 300 meters long and 0.05 meters wide, and some houses cracked. Therefore, the mine compensated for the loss of 654.38 million yuan.

4. Overexploitation causes the destruction of natural balance and the imbalance of natural ecological cycle.

Due to the over-exploitation of groundwater and poor management of surface water resources, the virtuous circle of resources and environment in Yantai coastal areas has been destroyed, leading to the destruction of natural balance. Due to the long-term drought and lack of rain, the groundwater dried up, the groundwater level dropped, and the ecological environment problems further expanded, which not only caused soil salinization, but also reduced the flow of rivers into the sea, soil erosion and intensified land desertification. Seawater intrusion also destroyed the ecological balance in this area. For example, in the seawater intrusion area along the coast of Laizhou Bay, more than 7,000 wells have been abandoned, and 4× 104hm2 of cultivated land has been affected, resulting in the cumulative reduction of grain production by (30 ~ 45 )× 108 kg, and 3,300×104m2 of cultivated land has become wasteland, which also leads to the damage of some industrial equipment and the decline of production efficiency.

Six, other environmental geological problems

1) foundation environment change;

2) mine water inrush;

3) Endemic diseases.