Assessment of geological hazards along the east route of the South-to-North Water Diversion Project (Shandong Section)

Jia Dewang, Wang Xuesen, Zhang Min, Zhu Chang

(Lunan Geological Engineering Survey Institute, Shandong Province, Yanzhou 272100)

About the author: Jia Dewang (1972—), male , engineer, mainly engaged in hydraulic environmental geological survey and research.

Abstract: The South-to-North Water Diversion Project is a grand project that has attracted worldwide attention. The geological disasters along the route and the geological problems that may be induced after the implementation of the project are of great significance to the project construction. Based on the collection of existing geological survey data, this article analyzes the existing geological hazards along the Shandong section of the East Route of the South-to-North Water Diversion Project, and then uses the comprehensive index evaluation method to evaluate them. Based on the evaluation results, the area along the line is divided into geological hazard-free areas. and mild geological disaster areas, and put forward corresponding preventive measures and suggestions.

Keywords: South-to-North Water Diversion; Types of Geological Hazards; Geological Hazard Assessment; Shandong

1 Overview of the East Route Project (Shandong Section) of the South-to-North Water Diversion Project

The East Route Project is the South-to-North Water Diversion Project An important part of the basic framework of the master plan of "four horizontals and three verticals", the Shandong section spans the western part of Shandong Province and passes through five cities in Shandong Province: Zaozhuang, Jining, Tai'an, Liaocheng and Dezhou from south to north. The total length of the north-south main canal is 486.8km. . After the water is transferred from Jiangsu Province to Shandong Province, it uses the Taierzhuang, Wannianzha and Hanzhuang three-level pumping stations to deliver water to the lower-level lake of Nansi Lake at the Hanzhuang Canal, and then lifts the water to the upper-level lake through the second-level dam, along the length of the Liangji Canal. The three-stage pumping stations of Gou, Denglou and Baliwan pump water into Dongping Lake, and then deliver water to Lubei and Jiaodong respectively after exiting Dongping Lake. The Shandong North Water Conveyance Main Canal crosses the Yellow River in Weishan and then flows to Linqing. It uses the Qiyi and Liuwu Rivers of the Shandong North Branch Canal to provide water sources for cities such as Xiajin and Dezhou. The Jiaodong Main Water Conveyance Canal lifts water from the Qinglong Gate of Dongping Lake, flows eastward on the south side of the Yellow River, and connects with the Yellow River Diversion to Qingdao Project through the main stream of the Xiaoqing River and the open irrigation canal outside the left embankment, and then transfers water to Qingdao and Yantai. This project costs a lot of money and has long-term significance. Therefore, in order to implement the project smoothly, it is very necessary to conduct scientific planning to "avoid hazards and promote benefits" and to investigate and evaluate geological hazards along the line.

2 Geological environment background

The Shandong section of the east-line project belongs to a warm temperate semi-humid climate zone with sufficient sunlight and four distinct seasons. The amount of precipitation decreases from south to north, and the distribution pattern of evaporation is basically opposite to that of precipitation. The project passes through the western part of the Shandong first-level neotectonic unit Central South Shandong-Shandong Shandong rising mountains and the central and southern part of the western Shandong Shandong-Northern Shandong subsidence plain. Landforms are divided into two major types: fluvial landforms and lacustrine landforms based on their origin. They can also be divided into six landform types: alluvial plains, alluvial plains, valley plains, erosion plains, erosion and denudation plains, and lacustrine plains. Typical soils are brown soil, sand ginger black soil, paddy soil, cinnamon soil and fluvo-aquic soil. The surface water system is developed. The project spans the three major river basins of Huaihe River, Yellow River and Haihe River from north to south. The larger rivers include Majia River, Tuhai River, Yellow River, Dawen River, Si River, etc. The lakes include Nansi Lake, Dongping Lake, and Nansi Lake. It is a long and narrow strip of lake extending from northwest to southeast, where the water diversion project passes. Dongping Lake is a flood detention area for the Yellow River and Wen River. The total storage capacity of the two lakes is about 1×109m3.

Figure 1 Geological hazard distribution map of the east route of the South-to-North Water Diversion Project (Shandong Section)

1—Soil desertification area; 2—Goaf subsidence prone area; 3—Karst collapse area; < /p>

4—areas prone to ground fluorosis; 5—land subsidence; 6—ground fissures; 7—zoning boundaries; 8—water diversion routes

The main structures along the Shandong section of the water diversion project They are nearly north-south tensional faults, including Juye fault, Jiaxiang fault, Sunshidian fault and Yishan fault. Controlled by structure, the strata developed along the line include Taishan Group, Sinian System, Ordovician System and Quaternary System. The underground coal resources are abundant and the mining volume is large. Zaozhuang and Yanzhou are important coal export bases in the country. The types of groundwater are mainly divided into pore water and carbonate rock karst water. The unit water inflow volume of pore water wells (holes) is 100~1000m3/(d·m), and the unit water inflow volume of carbonate rock fissure karst water wells (holes) is 500~ 1000m3/（d·m）. Large and medium-sized enterprises along the line mainly exploit karst groundwater. Units with large water demands include Zaozhuang Shiliquan Power Plant, Zouxian Power Plant, Liyan Power Plant and various city water companies. Some areas have been over-exploited due to excessive water intake.

3 Types of geological disasters

Geological disasters along the project line that are mainly caused by natural causes include collapse, water and soil erosion, etc.; geological disasters induced by human activities mainly include karst collapse, ground subsidence, Goaf subsidence, soil desertification, ground fissures, etc.

(1) Collapse: It mostly occurs in areas with steep terrain and relatively developed vertical joints. The upper rock layer is formed by the action of internal and external dynamics. The collapse point along the line is located at the northwest foothills of Taozhuang Town, Xuecheng District. The lithology of the collapse body is limestone. The upper part collapsed due to long-term weathering and erosion of the underlying shale. The collapse body is about tens of meters long.

(2) Water and soil erosion: The occurrence of water and soil erosion is affected by meteorology, hydrology, topography, vegetation, etc. It destroys farmland and also reduces soil fertility. Water and soil erosion along the line mainly occurs around the Tuhai and Majia river systems in the Shandong Plain, reducing flood drainage capacity by 30% to 50% on average and reducing surge prevention capacity by 25% to 40%.

(3) Karst collapse: The important basic condition for collapse is a large area of ??hidden carbonate rock. Collapse mainly occurs in Nanshi, Zaozhuang Shiliquan, Dingzhuang and Dongwangzhuang areas in Xuecheng District. The uncontrolled excessive exploitation of karst water by cities and industrial and mining enterprises has changed the dynamic conditions of groundwater in water source areas, eventually leading to karst ground collapse.

(4) Land subsidence: The occurrence of this disaster is a long-term slow-changing process and mainly exists in the urban areas of Dezhou City and the central district of Jining City, which have a concentrated population and developed economy. According to data, the subsidence rate has been increasing year by year since 1989. The range of subsidence is mostly consistent with the falling funnel of groundwater mining. The ground subsidence is uneven in the area. The areas with larger declines are mostly concentrated in the urban water supply sources.

(5) Goaf subsidence: The subsidence points are located in Taiping, Huancheng, Daizhuang and Zaozhuang City in Jining City. The subsidence area and the scope of subsidence tendency are about 3000km2. The occurrence of this disaster seriously damaged the regional ecological environment, lost large areas of land, forced villages to relocate, and caused huge economic losses.

(6) Soil desertification: Saturated powder, fine, medium sand and loamy clay can all liquefy under certain conditions. Soil desertification along the line can be divided into moderate desertification and mild desertification. Moderate desertification Desertification areas are distributed near Xiajin County, with large areas, dense pits and sand piles, and strong wind erosion; mild desertification areas are distributed in Xiajin-Wucheng, south Linqing, northwest Liaocheng, Dong'a and other places, in addition to Liangshan County and Wenshang County There is also a small area of ??distribution at the junction of Yuankou and Guanyi.

(7) Ground fissures: Mostly related to human activities such as groundwater extraction and mining, they are mainly distributed in 17 natural villages in Wangzhuang Township and Wulin Office in Yicheng District, covering an area of ??about 15km2, and are mostly located in groundwater fall areas. Inside the funnel; In June 1977, ground cracks appeared on the asphalt pavement in the dormitory of Yanzhou Mining Machinery Factory. It was a single crack with a "V" shaped cross section, nearly S-N direction. The crack surface was rough, the lifting and dislocation was not obvious, and it was tensile; Lu, Weishan County The bridge ground fissures are distributed in the Luqiao-Nanyang Lake section, with weak directionality and no continuity. There is no horizontal displacement or up-and-down movement.

4 Geological hazard evaluation

There are no norms and standards at home and abroad for the evaluation of geological hazards. The comprehensive index method is used here. First, various geological hazards are classified according to Table 1. Score, and then use the comprehensive index (Formula (1), Formula (2)) to calculate:

Shandong Province Environmental Geology Collection

Shandong Province Environmental Geology Collection

In the formula: F is the average value of each component score Fi; Fmax is the maximum value of a single component score Fi; n is the number of participating evaluation indicators.

The comprehensive index of geological hazards is obtained, and then Table 2 is used for zoning. Based on the evaluation results, the project line is divided into no geological hazard areas and mild geological hazard areas.

Table 1 Geological hazard evaluation index table

Table 2 Geological hazard comprehensive index analysis standard table

(1) Geological hazard-free area: the geological hazard comprehensive index is less than 1. Mainly distributed in Liulin-Yanggu, Liangshan-Yutai, Liaocheng City, Wangzhuang, Tengzhou City and other places. This area belongs to alluvial plains and alluvial plains. The land is less erosive. Currently, there are no ground fissures, karst collapse, or Geological disasters such as land subsidence, goaf subsidence, and soil desertification.

(2) Mild geological disaster areas: geological disaster index 1 to 2.75, distributed in Dezhou-Xiajin, Jining-Taierzhuang and low mountain and hilly areas. Dezhou-Xiajin is mainly affected by geological disasters such as land desertification, land subsidence, water and soil erosion. The land desertification area is large and has reached moderate desertification; water and soil erosion occurs in the Majia River and Tuhai River basins of the Yellow River Plain in northern Shandong; land subsidence occurs In the urban areas of Dezhou and Jining, the degree of subsidence is relatively light; geological problems such as karst collapse, goaf subsidence, ground fissures, and collapse occur in Jining-Tengzhou coalfield, Xuecheng-Taierzhuang and other places.

5 Geological Disaster Prevention and Control Measures

(1) Implement the prevention-oriented approach and increase efforts in predicting and forecasting various geological disasters.

(2) According to local conditions, avoidance measures should be taken for new or proposed projects in existing and potential areas of geological disasters such as collapse, karst collapse, goaf subsidence, and ground fissures.

(3) Improve geological environmental protection laws and regulations, strengthen management, limit the extraction of underground resources in areas such as ground subsidence, karst collapse, and goaf subsidence, and strictly control over-exploitation.

(4) To treat the symptoms and root causes, biological management and engineering management measures can be adopted for certain areas. Use SNS flexible protection projects and concrete lattice reinforcement in collapse-prone areas; carry out afforestation in areas with soil erosion and soil desertification; build fluoride prevention wells in high-fluoride areas; and increase backfilling efforts for goaf subsidence.

6 Conclusions and Suggestions

(1) There are many geological disasters and geological problems along the project line, mainly including ground fissures, soil desertification, land subsidence, karst collapse and goaf subsidence, etc. .

(2) Use the comprehensive index method to evaluate geological hazards, and divide the areas along the line into no geological hazard areas and mild geological hazard areas.

(3) Strengthen early warning and forecasting measures for geological hazards and geological problems in the region to effectively contain and prevent the occurrence of disasters.

References

Duan Yonghou, Luo Yuanhua et al. 1993. Geological disasters in China. Beijing: China Construction Industry Press

Li Gongyan et al. 2003. Zaozhuang Basin, Shandong Province Discussion on the formation conditions of karst collapse and the division method of prone areas. Chinese Journal of Geological Hazards and Prevention, 12(4): 49～52