First, the ground deformation disaster
Ground deformation disaster refers to the geological disaster that occurs near the surface and is dominated by deformation, including ground subsidence, ground fissures and ground collapse.
1. Land subsidence
Land subsidence in the working area mainly occurs in Lubei Plain, namely Dongying City, which is mainly caused by deep groundwater exploitation and oil and gas exploitation.
1985, when the Institute of Geophysics of the State Seismological Bureau and the Seismological Bureau of Shandong Province carried out modern deformation measurement, it was found that the ground subsidence in Dongying City was 80 mm, and in 2000, the earthquake department carried out elevation measurement on some elevation points in this area, and the ground subsidence at the elevation points was 248 ~ 397 mm
From 2002 to 2003, the monitoring results of 43 land subsidence observation points in Dongying area were analyzed, and it was found that there were 7 points with subsidence of 30mm or more, 4 points with subsidence of 20 mm ~ 29 mm, 5 points with subsidence of 10mm or less, and the rest were 165438 points.
The above monitoring data of land subsidence show that the northern Shandong Plain is in a state of overall subsidence, and the land subsidence in some deep groundwater exploitation areas and oil field concentration areas has reached a certain scale, so a monitoring system of land subsidence in the working area should be established as soon as possible.
2. Ground fissures
Ground fissures are mainly distributed in Bohai Plain, mining areas, Yantai, Qingdao, Weihai and earthquake areas. Some ground fissures are caused by pumping and drainage, some are accompanied by ground subsidence, and some are the result of internal dynamic actions such as earthquakes. On June 65438+1October 65438+August, 2005, an earthquake of magnitude 4.3 occurred in Rushan, Shandong Province, and three ground fissures with a length of more than 20m were formed in Meijia Town, the macro epicenter. Ground fissures are derived geological disasters, which are potentially harmful, sudden, mass and uncontrollable when they develop obviously.
There is a ground fissure in the area of Yuli Town-Guanshuai Town-Wang Hu Town, Wulian City, Rizhao, which is in the northeast direction, with a total length of 25km and a width of about 2km, with a total area of about 100km2. At present, 28 villages in 3 towns and villages have been affected to varying degrees, with about 20,000 people affected, and houses have cracked13,875, of which/kloc-0 is uninhabitable and 500 houses have collapsed. There are transverse cracks in many places on National Highway 206; Deformation and cracks appeared in two dams and some canals. Its economic losses are huge and its hidden dangers are serious. The preliminary exploration results show that the main reasons are man-made factors such as tectonic activity earthquake and nearby mining.
3. Ground collapse
There are two types of ground collapse in Shandong Peninsula. One is goaf collapse. In the process of mining, because the goaf is not filled or permanently supported, the upper strata sink under the action of self-weight, which leads to a large area of ground collapse. The other is karst collapse. In the area where carbonate strata are distributed, the dynamic conditions of groundwater change and the ground collapses due to uncontrolled over-exploitation of karst groundwater or improper mine drainage. Karst collapse in Shandong Peninsula urban agglomeration area is mainly distributed near Xindian water source in Zibo (Yin Jianzhong, 1996).
The second is the disaster of slope environment variation.
Slope environmental variation disaster refers to the overall collapse of rock, soil and sediment caused by gravity imbalance, including landslide, collapse and mud (rock) flow, which is complex, derivative, potentially harmful, widely distributed, sudden and collective, and most of them are controllable.
Collapse, landslide and debris flow mostly occur in the middle and low mountains and hills composed of metamorphic rocks, intrusive rocks and CAMBRIAN limestone, which have the characteristics of sudden and certain concealment, and once they occur, they often cause great economic losses and casualties. In the work area, geological disasters such as landslides, landslides and landslides have occurred in Jinan, Zibo, Yantai and Qingdao.
The main manifestations of gravity geological disasters are debris flow and collapse. In recent years, such accidents have occurred from time to time. Due to continuous rainstorm in Linglong Concentrator of Zhaoyuan Gold Mine, flash floods occurred in tailings pond, and tailings sand flowed down the river, which washed away more than mu of orchard 10, 25 mu of farmland and silted up small reservoirs 1 seat. The accident also silted up a 3-kilometer-long river, causing an economic loss of 350,000 yuan.
The formation of collapse, landslide and debris flow is closely related to topography and climate. It develops in the hilly areas of central and southern Shandong and eastern Shandong, and develops in Jinan, Zibo, Yantai and Qingdao. See Table 32 for a summary of the occurrence of collapses, landslides and mudslides in various cities.
As can be seen from Table 32 in the summary, collapse 138, landslide 67 and debris flow 74 have occurred in the working area. According to the investigation, most of the debris flow disasters in this area are debris flows formed by waste rock piles from mineral exploitation.
Three. Fluid disaster
Fluid disaster refers to various geological disasters caused by various fluids in mountainous areas, including coastal erosion, seawater intrusion, storm surge, tsunami, tail swing of the Yellow River, tunnel water inrush, harbor siltation and so on. These geological disasters have both internal and external causes, and the causes are complex. Most of the above geological disasters are potentially harmful, uncontrollable and mass (individual disasters can also occur alone), among which storm surge, tsunami and tunnel water inrush are also sudden.
1. Sea (salty) water intrusion
(1) Evolution history of seawater intrusion and distribution of key intrusion areas.
During the period of 1976, the long-term monitoring wells of groundwater dynamics in Shouguang, Hanting, Laizhou and other places in the work area found seawater (salty) water intrusion phenomena such as salty water quality and increased Cl- concentration for the first time. At that time, there were only a few isolated point intrusions, which developed slowly from the late 1970 s to the early 1980 s and the invasion area was small, which was the stage of occurrence. In the middle and late 1980s, the invasion area expanded rapidly, and the invasion speed reached the maximum. The whole Laizhou Bay is connected with the east and south banks, which is a rapid development stage. Since the 1990s, seawater intrusion has slowed down, and there is a weakening trend in some areas, which is a slow development stage.
According to the survey statistics, the total area of seawater intrusion in Shandong Peninsula at this stage is 135 1.7km2 (Table 8- 1).
Table 8- 1 Statistics of Sea (Salt) Water Invasion in Shandong Peninsula
(2) Evolution trend of seawater intrusion
The development of seawater (salt water) intrusion around Bohai Sea in Shandong Province has gone through three stages: ① in the early 1970s; ② the rapid development stage in 1980s; (3) Since the 1990s, due to the increase of precipitation, all localities have fully realized the harm of seawater (salty) intrusion and taken certain measures to limit exploitation, and seawater intrusion is generally in a slow stage.
Seawater intrusion on the east coast of Laizhou Bay mainly takes Quaternary strata as the intrusion channel. Because the underlying bedrock is metamorphic rock and granite, the water permeability is extremely weak, so the intersection line between sea level and the top surface of bedrock is the largest intrusion line in this area. According to this principle, the maximum line position of seawater intrusion can be determined. If effective measures are not taken to limit groundwater exploitation in Longkou Plain on the east coast of Laizhou Bay, the groundwater level will continue to decline, and seawater intrusion will eventually endanger the whole Longkou Plain, with the maximum intrusion distance reaching 14.2km, and the intrusion lines in other areas are close to the maximum intrusion line, and there will be no obvious expansion. Although the Quaternary system on the south bank of Laizhou Bay is thick, the salt water intrusion will not invade the inland indefinitely, but is related to the scale of the negative funnel of groundwater level and the position of the central axis of the funnel. The maximum invasion line is located in the south of the negative funnel, and the hydraulic gradient is just the position of the original hydraulic gradient. According to the analysis of the layout and degree of groundwater exploitation in the south bank of Laizhou Bay, the position and scale of the negative funnel of groundwater will not change greatly, so the maximum intrusion line can be determined according to the present situation of the funnel. In the future, the development of brine intrusion is mainly concentrated in Guangrao, western Shouguang and Changyi City, and will invade inland for 3 ~ 15 km in the future. Other areas are close to the invasion termination line, and the area will not be greatly expanded.
In Shandong province around Bohai Sea, except the coast of Laizhou Bay, seawater intrusion has occurred in the estuary plains of major rivers. The Quaternary distribution near the intrusion area is small, and the Quaternary basement has dense lithology and undeveloped cracks, which limits the seawater intrusion to some extent. In addition, the local government has taken a series of measures to limit the exploitation of groundwater in the invaded area, and the seawater intrusion has been curbed, and the scope of invasion in some areas tends to shrink. Therefore, in the near future, seawater intrusion in the above areas will generally maintain the status quo and will not change much.
2. Storm surge
The spatial distribution of storm surges along the coast of Shandong Province has certain regularity. On the south bank of Laizhou Bay, tidal spring storms are the main ones. The coast of the Yellow Sea is dominated by typhoons and storms, mainly in summer. At the beginning of June, a severe storm 1993 1 1 occurred in the south bank of Bohai Sea, which hollowed out most of the revetment dams on both sides of the Yellow River harbor and washed some oil field exploration dams into several sections.
The invasion range of storm surge to inland is 5 ~ 10km ~ 20 ~ 30k m. On July 1938, 17, the storm surge on the south bank of Bohai Sea invaded the land by 30km. 1On April 5, 964, the storm surge reached 4.77m, affecting 23,300 people in 5,305 households in 25 villages, causing 30,000 mu of farmland to be deserted. After the storm surge, plagues often spread, and seawater intrusion salinized a large area of farmland, polluted fresh water resources and deteriorated the ecological environment. Its side effects are often difficult to eliminate for several years, especially the impact on agricultural production is often long-term.
3. Coastal erosion
The coastline of Shandong Peninsula is 3 1 and 2 1km long, which is mainly composed of bedrock coast (accounting for 2/3, mainly distributed in the east, southeast and northeast coast of Shandong Peninsula), muddy coast and sandy coast (mainly distributed in Lubei coast, Laizhou Bay and Jiaozhou Bay). Coastal erosion is a disastrous coastal geological phenomenon with various forms and different degrees. Coastal erosion in Shandong Peninsula has brought serious economic losses to coastal residents and posed a serious threat to coastal economic development.
The areas with serious coastal erosion in the working area are Penglai-Qimu Island and the Yellow River Delta coast.
4. Siltation in ports, reservoirs and bays
Siltation in ports, reservoirs and bays is usually caused by two aspects. One is that soil erosion in adjacent land areas brings a lot of sediment to the sea area; Secondly, the unreasonable coastal engineering layout changes the seawater flow field and siltation occurs. The former is JIAOZHOU bay. Compared with the areas of 1980 and 1935, the total area of JIAOZHOU bay has decreased by 1 12km2 (Gao Zhenhua,1985; Wang Wenhai, 1985), the average annual decrease is 2.8km2, and the average annual decrease of tidal flat is 2.5km2. Nine rivers in Yantai and Weihai discharge 577.7× 104m2 of sediment every year. Weihai Yao Yuan Wharf was built at 1963 with an investment of 800,000 yuan. It only took 10 years to be silted up and scrapped. There are many examples of erosion and deposition changes in sea areas caused by unreasonable coastal engineering layout. For example, the unreasonable coastal engineering in front of the first and second beaches in Qingdao changed the flow field, resulting in the sand in the two beaches being taken away to varying degrees.
5. Other fluid disasters
The tail swing of the Yellow River is mainly distributed in the Yellow River Delta. Since 1855, there have been 45 breaches in the Shandong section of the Yellow River, which has high sediment concentration and is easy to deposit, measure and migrate. The Yellow River is a suspended river on the ground, so dredging and strengthening the riverbank is very important to prevent and reduce its harm.
Tunnel water inrush is mainly distributed in Zhao Ye Gold Mine. Tunnel water inrush is a serious geological disaster in Shandong Province in recent years, which mainly comes from cross-border mining, indiscriminate mining and improper drainage.
Four, the water and soil environment variation disaster
All the deterioration phenomena of water quality and soil quality belong to the variation of water quality, including groundwater pollution, soil erosion, sand liquefaction and land salinization. Most of these geological disasters are caused by external power, and they are all potential hazards. Except for groundwater pollution, the rest are derived geological disasters; Except sand liquefaction, it can be controlled; The liquefaction of sand is sudden.
Verb (abbreviation for verb) Other geological disasters
1. Potential geological disasters
Potential geological disasters mainly refer to disasters that could have been avoided, but were caused by unreasonable planning. The most important thing is to build the project on the fault zone, which is like burying a bomb under the building. This situation can be seen in many cities.
2. Ancient rivers and tidal gullies
Ancient rivers are mainly distributed along the Bohai Sea, Laizhou Bay and the Yellow Sea. The variability of lithofacies and the structural instability of ancient river channel (seabed) are the limiting geological disaster factors that hinder coastal and submarine engineering.
Ancient tidal gullies are mainly distributed in Laizhou Bay and the shallow sea area in the west of the Yellow Sea. Because of the difference in lithology between the inside and outside of the ancient tidal ditch, the metastability of its engineering geological environment is determined.
3. Submarine uplift and diapir
Submarine uplift is mainly distributed in Laizhou Bay and Yellow Sea. No matter the tectonic origin, gravity or erosion, submarine uplift constitutes a laterally unstable geomorphic unit, which is an obstacle to engineering construction.
The diapir is mainly distributed in Laizhou Bay and the Yellow Sea. Diaphragm is an image of submarine uplift caused by tectonic activity or density difference, which is characterized by instability and is a limiting geological disaster factor that submarine engineering should avoid and focus on defense.
4. Gas phase disaster
Gas phase disasters refer to various geological disasters caused by underground natural gas and other gases, mainly shallow seabed gas. The reasons are complex, potentially harmful, sudden, single and uncontrollable.
Shallow seabed natural gas is mainly distributed in Bohai Bay, Laizhou Bay and the offshore seabed of the Yellow Sea. Natural gas in seabed loose sediments forms sand blasting and mud mountain under the action of external forces such as structure and drilling, which can subvert offshore drilling platforms and is a potential danger source of submarine engineering.