(1 Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Beijing,10159; 2 Shandong Bureau of Geology and Mineral Resources, Jinan, 250014; 3 Shandong Institute of Geology and Mineral Resources, Jinan, 2500 14)
The eastern part of Jinan has simple topography, little change in stratigraphic lithology and lithofacies, general geological structure complexity, good hydrogeological conditions and geotechnical engineering geological properties, and environmental geological conditions are suitable for the planning and construction of industrial belt. However, human engineering activities such as iron ore mining, road construction and real estate development in this area are fierce, which may potentially induce geological disasters such as goaf collapse, ground fissures and collapse, and do harm to the planning and construction of industrial belt. Therefore, some important construction projects should try to avoid the danger zone of geological disasters.
Keywords geological environment, geological disaster industrial belt, Jinan city
order
The eastern industrial belt of Jinan is located in the east of the main city. On the basis of the traditional industrial zone and high-tech industrial development zone represented by Jigang, it is planned to develop and form an important national software industry base, a high-tech industry and high value-added manufacturing corridor around Bohai Bay, a new industrialization base in Shandong Province, a technological innovation base and an industrialization base of high-tech achievements. The planned construction land is about 120km2, with a population of 700,000 ~ 900,000.
1 Overview of geological environment conditions
1. 1 landform
The industrial belt is located in the piedmont zone of hilly and mountainous areas, and its landform type is simple, belonging to denudation and accumulation landform type. The open plains and hills alternate with each other, and the hills are mostly round steamed buns, mainly including Weizishan-Qiushan-Huangyushan (elevation 250 ~ 3 10m) and Fenghuang Mountain (elevation 2 18m), and the slope of the hillside is generally 10 ~ 30. The vegetation on the mountain is good, mainly drought-tolerant evergreen conifers and shrubs.
1.2 meteorology and hydrology
Jinan is located in the warm temperate zone and semi-humid continental monsoon climate zone. According to the precipitation data from 1952 to 2000, the annual average precipitation is 644.60mm, the annual maximum precipitation is 1253.85mm( 1964), and the annual minimum precipitation is 378.7mm( 1999). The maximum daily rainstorm is 334 mm (1August 26th, 987).
This area belongs to Xiaoqing River system, and the rivers flowing through this area mainly include Ganggou River and Juye River, which are seasonal rivers. Only when there is heavy rain in the flood season, the mountain torrents are discharged for a short time and dried up after the rain.
1.3 Geological and Mineral Geological Survey
In general, the eastern part of Jinan is a monoclinal structure with Paleozoic strata as the main body and tilted to the north. The strata exposed in this area are mainly Ordovician carbonate rocks mixed with clastic rocks. The Cenozoic Quaternary loose deposits are widely distributed in piedmont and valley areas, and the thickness gradually increases from south to north. Yanshanian gabbro is exposed in Dunqiu area.
The Ordovician strata in this area are relatively complete, and karst mainly develops along the strata. There are some cracks, grooves, fissures and honeycomb-shaped dissolved holes on the surface, but there are generally no large caves. Borehole data show that the underground karst is mainly vertical dissolved fractures, and there are small dissolved pores and holes in some areas, which can reach several centimeters in diameter.
Quaternary is mainly distributed in piedmont plain, mountain valley and piedmont slope, with variegated clay and red, purplish red sandy and silty clay mixed with gravel as the main lithology, and the thickness changes greatly, and the overall trend is to gradually thicken from mountain valley and piedmont slope in the southern mountainous area to the northern plain.
There are NW-trending faults in this area, such as Ganggou fault, Suncun fault and Wu Dong fault, which are mainly developed in Paleozoic strata, among which Wu Dong fault is a regional large fault and is generally considered as the eastern boundary of Jinan spring area.
The main mineral in this area is iron ore, and its genetic type belongs to skarn contact metasomatic iron deposit. The structure of the mining area is simple, and the main ore-controlling structure is a short-axis anticline formed by the intrusion of basic diorite in the middle Yanshan period, which arches the middle Ordovician limestone. The ore-forming mother rocks are pyroxene diorite and syenite diorite. These rocks are also carriers that carry mineral liquids up. The surrounding rocks are Ordovician limestone with weak alteration, mainly skarn and marble. It mainly occurs in the periphery of igneous rocks and has the characteristics of shallow burial, rich grade and small scale. The ore bodies are mostly layered, lenticular and irregular [1].
1.4 engineering geological characteristics of rock and soil mass
The rock mass in the area mainly includes hard massive magmatic rock mass and hard thick layered limestone mass. Soil is mainly divided into two types: mountain valley loose accumulation type and piedmont plain loose accumulation type. Among them, the loose accumulation type of intermountain valley is mainly distributed in the plain area of intermountain valley, with the thickness ranging from several meters to more than ten meters, and the soil is a single-layer cohesive soil. The types of loose accumulation in piedmont plain are mainly distributed in piedmont alluvial-diluvial plain and mountain slope. The lithology is mainly silty clay and muddy gravel layer. The rock and soil in this period can generally be used as the natural foundation of industrial and civil buildings [2].
1.5 hydrogeological conditions
1.5. 1 regional hydrogeological conditions
The industrial zone is located in the karst water recharge runoff area in Baiquan Spring Area, adjacent to Wu Jia in the north, and is a karst water-rich area (water source area in Wu Jia), with a buried depth of 45 ~ 60m, a single well water yield of 1000 ~ 5000 m3/d, a limestone roof buried depth of about 200m, a Quaternary thickness of more than 20m, and an aquifer buried depth of 220 ~ 270 m. ..
1.5.2 Hydrogeological survey of mining area
The main aquifer in the mining area is the fractured karst aquifer of Majiagou Formation of Ordovician, and the water quantity changes with the development of karst fractures, with the permeability coefficient of 1 ~ 10m/d, and the water quantity is generally about 1000m3/d ... The aquiclude is dense diorite, magnetite, etc. , located at the bottom of the aquifer, plays the role of water blocking and plugging.
1.6 human engineering activities
In recent years, with the rapid economic development and frequent engineering geological activities in Jinan, the resulting adverse geological phenomena are on the rise. In the process of mountain quarrying and highway construction, the original stress structure is destroyed, which is easy to cause slope instability and may lead to geological disasters such as collapse and landslide.
In addition, relevant information shows that iron ore mining in this area has a long history. Due to the long-term mining of iron ore in this area, many mined-out areas have been formed, and many ground collapses have occurred in some areas, such as Tang Ye to Xingcun, Kangshan Breeding Factory, etc., resulting in abandoned farmland and cracking of some buildings, posing a threat to nearby roads and civil buildings.
2 Geological hazard risk status
2. 1 main disaster types
Generally speaking, the main types of geological disasters affecting construction planning are collapse, landslide, debris flow, ground collapse, ground fissure and ground subsidence.
According to the geological environment conditions in the area, the planning area of industrial belt generally does not have the basic conditions of landslide, debris flow and land subsidence. However, due to the influence of human activities such as mineral development, roads and real estate construction, geological disasters such as goaf collapse, ground fissures and collapse have occurred in this area to varying degrees. Goaf collapse and ground fissures will have a great impact on the planning and construction of the eastern industrial belt.
2.2 Geological hazard risk assessment
The assessment of the present situation mainly determines the danger of geological disasters according to their scale, degree of harm and stability. Because the ground fissures in this area are accompanied by goaf collapse, the two disasters are evaluated together.
2.2. 1 basic situation of goaf
The distribution of mined-out areas is consistent with that of Guodian iron mine, and they are all distributed in the marginal zone of Tang Ye-Xingcun rock mass and Dunqiu rock mass. Guodian iron mine located in this area was built in the early days of the founding of the People's Republic of China, and there was no overall design. The development mode is mainly the combination of double inclined shaft, central double inclined shaft and inclined shaft, and the underground transportation adopts decentralized transportation mode, and the transportation alleys in each stage go straight to the main shaft; Because the ore bodies are scattered, small in scale and complex in shape, the mining methods mainly include small sublevel open stope method, high sublevel open stope method and sublevel caving method, and the mining depth varies from ++ 10m (horizontal elevation, the same below) to-70m. Long-term mining has formed mined-out areas with different scales and vertical multi-layer distribution.
2.2.2 goaf collapse and risk assessment.
According to the field investigation, four small ground collapses (see table 1) were found near Kangshan, Tangyexingcun, Diaoyutai and other mining areas, mainly in the form of small collapse pits, square or round in shape and about 10~20m ~ 20m in diameter. The inducing dynamic factor is the roof caving in iron ore mining roadway, and the main influencing objects are farmland, roads, etc., accompanied by building cracking.
Table 1 ground subsidence investigation
Generally speaking, the scope and scale of the collapses that have occurred in this area are small, causing less harm, but the collapses in Kangshan and Xingcun North are still unstable. Therefore, the present situation of goaf collapse risk in these two places is evaluated as large; The other two places are stable and the risk situation is assessed as small.
Analysis of the influence of 3 on industrial belt planning and its prevention and control countermeasures
3. 1 Analysis of the influence of geological environment conditions on the planning and construction of industrial belt
From the analysis of geological environment conditions in the area, the terrain in the area is simple, the lithology and lithofacies of the strata change little, the complexity of geological structure is general, and the hydrogeological conditions and geotechnical engineering geological properties are good, which is suitable for the planning and construction of industrial belt. The impact on industrial belt planning and construction is mainly manifested in the following aspects:
(1) Due to the good geological conditions of geotechnical engineering, natural foundation can be directly used for ordinary buildings; For high-rise buildings or buildings with heavy loads, the foundation excavation depth is not large, so it is generally unnecessary to carry out dewatering treatment, which can greatly reduce the project cost.
(2) The deep and high-quality underground karst water resources in the area are abundant, which can basically meet the domestic water demand of the planned population and some industrial production water demand.
(3) The alternate distribution of low mountains, flat land and river valleys in the area is beneficial to the planning and construction of ecological environment and scenic spots.
(4) Due to the intense human engineering activities in this area, especially the long-term iron ore mining, many large mined-out areas have been produced, and several smaller mined-out collapses have occurred in some areas, which will have a negative impact on the planning and construction of the industrial belt.
3.2 Analysis of the Impact of Geological Disasters on the Planning and Construction of Industrial Belt
Judging from the present situation of geological disasters, Wujiang-Dongdunqiu, Gaoerzhuang-Nandunqiu, Tang Ye-Xingcun and Zhang Ling are all located in the mined-out area of iron mine. Although the original mining area has been closed, there are still sporadic small mines, which makes the goaf unstable and the risk of geological disasters is high. The impact on industrial belt planning and construction is mainly manifested in the following two aspects:
(1) Potential hazards of goaf collapse and ground fissures to the proposed project.
This paper mainly analyzes the proposed road project from two aspects: first, the distance between goaf collapse and ground fissure and the proposed road; The second is the stability of goaf collapse and ground fissure itself. According to the survey of the above mined-out areas and the subsidence and ground fissures in the mined-out areas, Tang Ye-Xingcun, Shagou, Dongdunqiu, Kangshan, Dongshanpo, Diaoyutai-Liuhai, Duanjiafen and Zhang Ling are about 10 ~ 300 m away from the proposed highway, and the mined-out areas in Tang Ye-Xingcun and Kangshan have collapsed (or ground fissures) many times. In addition, in these mined-out areas, there are still sporadic small mines being mined and dug indiscriminately, which further increases the unstable factors. Therefore, the proposed road is dangerous.
(2) The possibility of inducing and aggravating geological disasters by construction projects.
First, in road construction projects, subgrade soil is generally compacted by vibration, which has a certain impact on nearby mined-out areas because of its high frequency and strength; Then, after the road is opened to traffic, the vibration generated during the driving of the vehicle will also have an impact on the nearby goaf. Therefore, in a sense, road construction will affect the stability of mined-out areas, aggravate or even induce new ground collapse.
3.3 Prevention and control countermeasures and suggestions
(1) Strengthen investigation and avoid it appropriately. First of all, we should try to avoid planning and constructing important engineering projects in geological disaster risk areas; If some linear projects, such as roads and pipelines, must pass through areas with high risk of geological disasters, it is suggested that before the design, in addition to the routine engineering investigation according to the relevant Code for Engineering Geological Investigation, the goaf in key areas should also be specially required to be investigated, so as to keep a proper distance between the proposed project and the goaf.
(2) Clean up sporadic mines and keep the original mined-out area stable. The investigation shows that after the closure of state-owned mines in this area, the phenomenon of indiscriminate mining and excavation of individual small mines is serious, and the mining has not stopped yet, which directly affects the stability of the original goaf and increases the hidden dangers of disasters. Therefore, it is suggested that the relevant authorities take measures to control it.
(3) The excavation toe should be anchored for slope protection, and the soil slopes and gullies on both sides of the road should be lined for slope protection and greening, so as to keep the slope stable.
(4) Because this area is located in the recharge and runoff area of Jinan Spring and Wujiayan karst water sources, corresponding environmental protection measures should be taken to prevent pollutants from entering the groundwater and affecting the water quality of Jinan Spring and Wujiayan karst water sources downstream.
4 conclusion
The natural geological environment in the east of Jinan is good, which is conducive to the planning and construction of industrial belt. However, there are geological disasters such as goaf collapse, ground fissures and collapse in some areas, which are mainly related to artificial mining and engineering construction activities. At present, it has caused certain harm in some areas, and its degree of danger has a great influence on the planning and construction of the eastern industrial belt of Jinan city. After evaluation, in areas with high risk of geological disasters, measures such as appropriate avoidance should be taken in the planning of industrial belts to prevent the harm to engineering construction and avoid inducing or aggravating geological disasters.
In the process of writing, this paper refers to the Research Report on Urban Planning Space of Jinan City, the Geological Summary Report on Closed Pits in Guodian Iron Mine Area of Jinan, Shandong Province submitted by Jigang Group Company, the Report on Geological Disaster Investigation and Zoning in Licheng District of Jinan City submitted by Shandong Geological Environment Monitoring Station, and the Report of Jinan City, Shandong Province 1 ∶ 5 submitted by Shandong Institute of Geology and Mineral Resources (formerly 80 1 Team).
refer to
[1] Zeng Guangxiang et al. Shandong iron ore geology. Jinan: Shandong Science and Technology Press, 1998.
[2] Shandong Bureau of Geology and Mineral Resources. Atlas of environmental geology in Shandong Province. Jinan: Shandong Map Publishing House, 1996.