Study on construction diversion and cofferdam technology?

What is the specific content of construction diversion and cofferdam technology research? Zhong Da Consulting will answer your questions below.

1. After years of research and development, China's water conservancy and hydropower construction technology and technology have made great progress, and major breakthroughs have also been made in diversion and cofferdam construction technology. Because water conservancy and hydropower construction are mostly in sites with harsh environment, effective diversion and cofferdam must be implemented in order to effectively adjust the position of water resources without destroying the local natural environment. In the process of river diversion, it is necessary to analyze and discuss the uncertainty of local hydrology and water conservancy in detail, and choose appropriate and accurate calculation and design methods to design diversion schemes and specific diversion technologies to ensure the smooth development of related water conservancy and hydropower construction work.

2. Project overview

Yancheng Yundong Sluice Project is located at the intersection of Subei Irrigation Main Canal and Beijing-Hangzhou Grand Canal, 2.5km south of Chuzhou District, Huai 'an City. It is a single-stage sluice project connecting the Beijing-Hangzhou Grand Canal and the main irrigation canal in northern Jiangsu. The sluice, the left Yundong sluice, the Yundong hydropower station and the embankment of the main irrigation canal in northern Jiangsu form a flood control barrier under the Yundong sluice. Cofferdams during the construction period of the project include the construction cofferdam on the side of Beijing-Hangzhou Canal in the upstream of the sluice, the construction cofferdam on the side of the main canal in the downstream of the sluice, and the secondary cofferdam on the side of the main irrigation canal in northern Jiangsu (completed in April 2065438+2005).

3. Engineering geological conditions

3. 1 hydrometeorology

Yundong Taozha is located in Baima Lake area in the lower reaches of Huaihe River, which is located in the transitional zone between the north subtropical zone and the warm temperate zone. Influenced by monsoon circulation, it has the climatic characteristics of obvious changes in cold and summer, distinct four seasons and the same season of rain and heat. The annual average temperature is between 14~ 16℃, the frost-free period is 220~240 days, the average sunshine hours for many years are 2300h, the average evaporation for many years is 1350mm, and the average precipitation for many years is 931mm. The rainfall varies greatly during the year, and it is rainy season.

3.2 Geological conditions

According to the engineering geological survey report and the stratum profile of the working area, the engineering geology of the working area is general, which is divided into seven layers, namely plain fill silty clay mixed with light silty loam, light silty loam, light silty clay mixed with heavy silty loam, light silty loam, silty clay mixed with silty clay, and loam mixed with silty fine sand, with silt as the main component.

3.3 Groundwater

The groundwater in the exploration depth of the exploration area is mainly interstitial phreatic water and pore confined water in loose sediments, and the fifth layer has poor water permeability. The groundwater below the fifth layer is confined water, and the main aquifers are (6A), (7) and (8). The recharge mode is mainly lateral recharge, and the connectivity with surface water is poor. The average water level of confined water measured during the survey is about+4.2m. ..

4. Selection and design of cofferdam construction scheme

According to the hydrological data provided in the tender documents, the lowest water level of not less than 4.0m should be considered before the cofferdam built on the inclined channel of approach river.

4. 1 Design of soil cofferdam at inclined river side of approach river

In the open channel section of the inclined river leading to the river, the water retaining cofferdam is filled outward along the excavation line on the south side (right side) of the foundation pit, with a top width of 7.0m, a platform width of 3.0m, and an elevation of 40cm on the back. The original wooden stake is set on the platform with a center distance of 8m. According to the fortification standards provided in the tender documents, the main canal side of the inclined river is diverted for irrigation. Seepage-proof geotextile and 30cm-thick bagged soil are used for double protection to enhance its stability and erosion resistance.

4.2 Design of downstream cofferdam of sluice

According to the fortification standards provided in the tender documents, the water retaining level of the downstream construction dam of the Hetao sluice in Yundong River is designed as the highest water level of 6.0m in non-flood season. Considering the factors of wind, waves and superelevation, the design height of the dam crest should be 7.0m, the ratio of slope inside and outside the dam should be 1:5, and the width of the dam crest should be 6.0m. At the same time, wooden stakes with the original center distance of 40cm and the length of 8m are added at the back water surface and the joint between the cofferdam and the steel sheet pile cofferdam.

4.3 Design of Steel Sheet Pile Cofferdam

Steel sheet pile cofferdam is used in the narrow river near the lower sluice head. Steel sheet pile cofferdam is an effective method for deep-water foundation pit support, and it is a form of cofferdam with simple construction and clear structural stress. According to the actual situation of the inclined river level of the approach river, the water depth is about 4m, and the steel sheet pile cofferdam is adopted, which occupies a small river section and has strong scour resistance. The steel sheet pile cofferdam is connected by double-row Ⅳ Larsen steel sheet piles and 24# channel steel cofferdam φ 18 steel wire rope, filled with clay in the middle, with a width of 7m and a top elevation of 7.0m (1m high bagged soil cofferdam). The top and bottom elevations of the steel sheet pile are 6.0m-3.0m respectively.

4.4 Foundation pit enclosure design after cofferdam scheme adjustment

After the diversion inclined river cofferdam is changed from two cofferdams to a longitudinal cofferdam, the space of the foundation pit on the south side (right side) of the lower sluice head and chamber is reduced, and the river water outside the cofferdam has obvious influence on the foundation pit. In order to ensure the construction of the building, it is necessary to strengthen the foundation pit support and drainage of the lower gate head. The specific arrangement is as follows: 9m Larsen Ⅳ steel sheet pile is used for foundation pit support on the south side (right side) of the lower sluice head, with the elevation of the pile bottom at -7.5m and the elevation of the pile top at 1.5m, and the distance between the retaining structure and the bottom plate of the downstream navigation wall is 20cm. At the same time, eight groups of light well points are set along the cofferdam to strengthen the interception of river water outside the weir. The construction method is the same as the special scheme of foundation pit enclosure.

5. Cofferdam construction technology

The total amount of earthwork filled by the longitudinal retaining cofferdam on the inclined river side of the approach river is about15000m3, and the amount of clay filled by the steel pipe pile cofferdam is about 5000m3. According to the site situation, it is planned to gradually borrow soil from the foundation pit to fill the longitudinal soil cofferdam on the inclined river side of the approach river when pumping and draining the Zhatang River, and the insufficient soil source can be purchased.

5. 1 earth cofferdam construction

1) Earth Cofferdam Cofferdam Filling Construction Dam Root Cleaning → Cofferdam Earthwork Filling Construction → Earthwork Filling and Compaction in Layers → Slope Repairing → Scouring Prevention and Sandbags. 2) Debris and silt cleaning: In order to ensure the soil quality of the cofferdam, excavators or bulldozers are used to remove the roots, turf and other debris with a surface thickness of about 40cm in the borrow area. Before the cofferdam is filled, the surface of dam root shall be cleaned by excavators and bulldozers to ensure that the cofferdam is embedded in the river bank and the anti-seepage effect of the connecting section shall be ensured; Mud at the bottom of the weir is removed by earthwork extrusion. 3) Cofferdam filling construction: occupation method is adopted. After the fill is 0.5m higher than the river surface, it will be leveled and compacted in layers by bulldozer. The cofferdam is filled with water, and the layered filling and tamping scheme is adopted, with a layer thickness of 25cm, leveled and compacted by bulldozers, and sufficient slope is made. The construction cofferdam of this project adopts dump trucks to load excavators, bulldozers to push the earth, occupy, level and tamp the earth, and the excavators cooperate with the finishing. 4) Leveling and compaction: After the cofferdam comes out, it will be compacted to the design elevation by layers with bulldozers, and the back water slope will be built in time, and other scour prevention or reinforcement measures will be constructed as required. 5) Construction of original wooden stakes and anti-scour sandbags.

5.2 Steel Sheet Pile Cofferdam Construction

The construction procedure of steel sheet pile cofferdam is as follows: piling of steel sheet pile → fixing and pulling of transverse I-shaped steel cofferdam → fixing bamboo raft with geotextile → filling construction of clay core wall of cofferdam → leveling, compacting, stacking and bagging the soil at the top of cofferdam.

1) steel sheet pile construction: the steel sheet pile is driven by piling boat.

2) Fix two transverse I-beams around the ridge and pull the wire rope.

3) In the construction of bamboo basketry geotextile enclosure, in order to prevent soil loss between piles, bamboo basketry geotextile enclosure is adopted, and bamboo basketry can be fixed on steel sheet piles through iron wires.

4) Filling construction of clay core wall of cofferdam: the clay is directly excavated by excavator at the site and transported to the mud barge, and the excavator is transported to one side of the completed sheet pile cofferdam (placed and fixed on the engineering ship). The clay filling between steel sheet piles starts from the north bank, and the water part is compacted by small machinery and backfilled to the designed pile top elevation in layers. During the process, pay attention to the consolidation of wire rope. 5) The bagged earth dump is highly protected.

For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd