Hydrology of Wuxi section of Sunan Canal?

Reference: Overview of Jiang Ye Sunan Canal Revetment Project of Jiangsu Transportation Planning and Design Institute 2 10005 Abstract: Based on a comprehensive description of hydrology, engineering geology and topography along Sunan Canal, the structural forms of waterway revetment are introduced, and the design and construction of concrete precast block, Fab revetment, gravity revetment and counterweight revetment are further introduced in detail.

Key words: overview of canal revetment project 1. The south section of the Beijing-Hangzhou Canal (also known as the South Canal) starts from Jianbikou Gate on the south bank of the Yangtze River in the north and ends at Duck Dam at the junction of Jiangsu and Zhejiang in the south, with a total length of 208.2km? It runs through the economically developed cities of Zhenjiang, Changzhou, Wuxi and Suzhou in Jiangsu.

The Sunan Canal is reserved according to the third-class channel standard, and the fourth-class channel standard is implemented. The minimum water depth of the waterway is 2.5m, the general river bottom width is ≥40m, the revetment spacing is ≥60m, the minimum bending radius is ≥600m, the clear width of the navigation hole of the river-crossing bridge is ≥50m, and the clear height is ≥7m (above the designed maximum navigable water level). The designed largest ship type is a 4×500t towing fleet, taking into account the 6×300t,1100t, 12×60t towing fleet, and the 2×500t pushing fleet is navigable.

The renovation project of Sunan Canal started in August 1992 and was completed in September 1997. 156.56k m, including Zhenjiang section 23. 1 12km, Changzhou section 35.5 17km, Wuxi section 24.946km and Suzhou section 72.986km. At the same time, 286.03km of new revetment was built, including 45.82km of precast concrete revetment, 4. 1 1km of stone revetment and 3km of stone revetment. 236. 1 km.2 Basic data 2. 1 design water level

The design characteristic water level adopts the 30-year series data of hydrological stations along the waterway, and carries out hydrological analysis and calculation in combination with water conservancy planning. The high water level once every 20 years is the designed maximum navigable water level, and the low water level with 98% guarantee rate is the designed minimum navigable water level. See table 1 for the characteristic water level along the canal.

2.2 Geological and Geomorphological Features

2.2. 1 Topographic features

The Sunan Canal, from Jianbikou Gate in Zhenjiang to the north of Danyang City, is a hilly area extending from Ningzhen Mountain Range. The mountains on both sides of the river are undulating, with occasional residual hills. The landform belongs to the first terrace type of the Yangtze River floodplain. Due to the scouring and cutting of water flow, the abrupt change of scarp is formed, and the ground elevation is generally around 10m (Wusong elevation zero base); The south of Danyang enters the Yangtze River Delta, where a large amount of sediment carried by the Yangtze River continues to deposit, forming a vast delta plain. The ground elevation is generally 5 ~ 10m, which is high in the northwest and low in the southeast. Changzhou extends eastward to the north of Wujiang in Suzhou, with a ground elevation of 3 ~ 5m. Taihu Lake water network plain, which belongs to the accumulation plain area of Taihu Lake Basin, has dense river network and developed water system, and is lake facies or limnetic facies. The area from Sanli Bridge to Bati in Wujiang belongs to the plain of lakeside polder area, and the ground elevation is about 4m, which is lacustrine deposit. From the south of Bati to the duck dam, it belongs to the low-lying lake swing plain. Jiang Ye: Overview of the bank protection project of Sunan Canal, with dense lakes and waves, the ground elevation is 1 ~ 3m, which is the lowest terrain of Sunan Canal. Unit: m Design water level table of the highest navigable water level of Sunan Canal (Wusong base) 1.

Minimum navigable water level (once every 20 years)

(98% guarantee rate) At normal water level, the walls are 7.02.55.0, Danyang 7.02.54.0 ~ 4.5 Lingkou 6.82.54.0 ~ 4.5 Changzhou 5.32.53.6 Wuxi 4.72.53. 1 Wang Ting 4.32.5 ~ 2.

Zhenjiang section

(1) Jianbi to Danyang Ren Minqiao. The main sedimentary layers are gray, yellowish gray or grayish yellow loam and clay layers, which are in a hard plastic state, with medium compressibility and good soil quality. Due to the cutting action of valleys or rivers in the later period, grey loam layer is intermittently deposited on the upper part, and the soil quality is poor. Affected by the sedimentary environment of the Yangtze River, the soil quality in Jianbi-Yuehekou section is slightly different. The upper part 2~3m is yellow gray and grayish yellow, and the lower part 6 ~ 1m is grayish yellow silty sand mixed with thin clayey soil. ..

(2) Ren Minqiao-Lucheng section. The upper part is brownish yellow and yellowish brown loam, which is hard and plastic, and the local part is cut from soft soil deposited by gullies. Near Lucheng, below 0 above sea level. 0m, with grayish yellow and grayish loam mixed with silty sand or silty sand layer, saturated and loose. The sandy property of this layer gradually becomes larger from west to east, which is easy to cause quicksand during construction and excavation.

Changzhou section of 2.2.2.2

(1) Jiuli to West Culvert Section. The upper part is gray, grayish yellow clay or loam, with a thickness of 3 ~ 5m, hard plastic, medium compressibility and good soil quality; The middle part is grayish yellow and gray loam mixed with silty sand, which is soft and plastic, and the elevation at the bottom is below 0.0m Niu Ben Town and Wuxing Bridge are cut by gullies, and gray loam mixed with silty sand is deposited, with different thicknesses, and the thickest part is about 10m. The lower part is gray and yellow-gray silty sand mixed with cohesive soil, which is saturated and slightly to moderately dense.

(2) Changzhou Third Bridge to Zhihu Port. The upper part is brown, grayish yellow clay or loam, which can be plastic to hard plastic state, with medium compressibility and layer thickness of1~ 5m; The middle part is grayish brown loam mixed with silty soil, soft and plastic, with a layer thickness of 1 ~ 7m. However, in the east and west of Henglin Town, this layer is replaced by gray muddy loam, and the thickest part is 65438. In addition, between the Third Bridge and Qishuyan, there is a layer of grayish yellow silty sand with different thicknesses. The lower part is gray and grayish yellow loam, which can be plastic to hard plastic state and has good soil quality.

Wuxi section of 2.2.2.3

The soil quality in the eastern and western sections of Wuxi is similar, and the upper part is grayish yellow, grayish brown clay, clay, iron-bearing manganese nodules, hard plastic state and medium compressibility. Due to the late gully cutting, gray muddy clay is intermittently deposited on the top, which looks like an inverted cone. The middle part is grayish yellow, grayish loam mixed with silty sand, soft to plastic, moderately compressed, with a layer thickness of 2 ~ 4m, and the lower part is grayish silty soil, slightly dense to medium dense, with a layer thickness of 6 ~ 8 m, which is common in the east of Wuxi. The lower part is green-gray, gray-yellow loam and clay layer, which is in a hard plastic state, with a small amount of gray soft loam and rotten plants locally.

Suzhou section of 2.2.2.4

(1) section from Wangting to Qiao Feng. The soil quality is similar to Wuxi section, except that there is a layer of taupe clay about 2 meters near the surface in the east section of Xingxian Bridge in Huguan, which can be plastic to soft plastic state and has medium and high compressibility.

(2) baodai bridge-Lisan Bridge. The upper part is grayish yellow clay and loam, containing iron and manganese, which can be plastic to hard plastic state and has medium compressibility. This layer has good soil quality, with a thickness of 4 ~ 5m and continuous distribution. On the other hand, in the south section of Wusong Port, there is a layer of gray muddy clay with the thickness of 1.4 ~ 6.65m at the top, which is plastic and has high compressibility. The middle part is grayish yellow loam mixed with silty sand, which is in plastic ~ flowing plastic state with moderate compressibility, and the lower part is grayish loam mixed with silty sand or interbedded with silty sand with 2 ~ 4m thickness, which is soft ~ flowing plastic, moderately compressed, with different thicknesses and widely distributed. The bottom is gray silt, slightly dense to medium dense, and the general roof elevation is below-7.00 m.

(3) Section from Lisan Bridge to Yaziba. The upper part is grayish yellow and grayish yellow loam, which is plastic, locally soft and moderately compressed, with a layer thickness of1~ 2m; The middle part is gray muddy loam, clay or silt, which is plastic and has high compressibility. This layer is thick in the south and thin in the north, with the thickness of 10 ~ 15m and the thickest part exceeding 20m. The lower part is grayish yellow clay and silty sand mixed with loam. This layer is mainly distributed in the northern part of Wang Ping, and it is intermittently distributed by gully cutting in the later period. The roof elevation is about 0.0m, and the layer thickness varies from 5 to 5 to 8m. According to the overall design principle of Sunan Canal, the revetment engineering structure is designed according to the fourth-class channel standard, and considering the third-class standard planning, it can be used for navigation of thousand-ton ships in the future. At the same time, in order to meet the requirements of reducing the navigation resistance of ships, reducing the project cost and operating cost, and facilitating the construction, combined with the terrain characteristics along the route, the channel section design mostly adopts rectangular and inverted trapezoidal sections.

Generally, vertical or semi-vertical revetment structure is adopted in the market town section of the South Jiangsu Canal with rectangular cross section, which is not only beneficial to the waterway, but also can minimize the influence of urban demolition and mining enterprises along the route and improve the environmental conditions of the market town. Through technical and economic comparison, the revetment retaining wall structure adopts mortar rubble gravity wall and counterweight wall, with the wall height of 3.5~6.0m, the wall bottom plate higher than the bottom of the channel 1.0 ~ 1.5m, and the platform reserved in front of the wall is connected with the bottom of the gentle slope river, which can not only protect the wall foundation, reduce the scour in front of the wall, but also leave room for the future implementation of the third-level channel, and the height of the wall top is the same as that of the bank. From the perspective of construction application, this structural form can adapt to the geological conditions in southern Jiangsu, make full use of the rich local stone resources, and has the advantages of low cost, simple structure, convenient construction, accelerated construction progress, strong anti-erosion and anti-collision ability.

The inverted trapezoidal section is a rural section other than the market town section. Except that the bank slope is sandy soil and concrete slope protection is considered, the original design of other river sections adopts undisturbed soil exposed slope to save engineering investment and reduce engineering quantity. The slope ratio is controlled by the overall stability of the bank slope, which is generally 1∶3, forming an inverted trapezoidal section. Later, in the specific implementation process, the bare slope was cancelled and changed into a small revetment structure, chemical fiber (fabric) or concrete block revetment structure. Through the technical and economic comparison of dry block stone, mortar rubble, precast concrete block and cast-in-place concrete block, the slope protection structure adopts the form of laying permeable nonwoven geotextile (thickness 7 ~ 9 cm) under precast concrete block. In order to increase the overall stability of slope protection, mortar stone ridges are set at the top, toe and middle of slope. This kind of slope protection structure is characterized by simple structure, convenient construction and low engineering cost, which can effectively prevent ship waves from scouring the bank slope, but the disadvantage is that concrete blocks are easy to be damaged and difficult to repair after being hit by ships.

This revetment structure is widely used in some sections of Zhenjiang and Changzhou, but in Luoshe Township, the western section of Wuxi, in order to reduce the influence of construction cofferdam on the navigation of ships, the Fab revetment structure is adopted, and the concrete is directly poured underwater on the slope after being leveled by dredger. This kind of slope protection structure does not need to build cofferdam, which is beneficial to uninterrupted navigation construction and less earthwork. The thickness of formwork bag concrete is 15cm, which has good integrity and can effectively resist the collision between ships, but it is generally suitable for bank slopes of clay or loam.

In addition, in the rural section of Suzhou Creek, within a distance of nearly 5km, the backward retaining wall structure of slurry block stone is adopted, the wall height is within 3m, the slope behind the wall is 4∶ 1, and the slope ratio between the wall body and the water surface is 2.04∶ 1. 4 Design and construction of revetment structure 4. 1 Precast concrete block revetment

Taking precast concrete slope protection in waterway regulation of Lingkou section of Danyang Canal in southern Jiangsu as an example. In view of the fact that the river geology in this section is dominated by extremely fine sand, and the fourth layer is Holocene (Q4) modern sedimentary layer, with various soil interlayers such as loam, peat, silt and miscellaneous fill, the designers choose the construction method of light well point drainage along the river to reduce groundwater. 400g/m2 nonwoven geotextile is used as the filter layer, and its main physical and mechanical properties are shown in Table 2. Table 2 Project unit area weight thickness breaking strength elongation ratio index 400 g/m 23.5 mm ≥ 600 N/5 cm ≥ 80% <1.5 Project trapezoidal tear strength, bead bursting strength, effective pore permeability coefficient porosity index ≥ 400 N ≥ 900 N ≥ 0.1mm ≥ 5×/. S≥90% Compared with the traditional gravel filter layer, geotextile not only has the functions of water permeability and sand retention, but also has the characteristics of stabilizing the slope, that is, geotextile binds the soil slope into a whole and plays an important role in preventing the slope from collapsing. According to the calculation, the unit cost of using geotextile is 15% ~ 20% less than that of traditional sand and gravel filter layer. After 6 ~ 7 years' delivery, it has not only remarkable economic benefits, but also excellent engineering quality, and has become one of the most used segments of inland waterway in China.

Special attention should be paid to the construction of concrete precast block slope protection structure: geotextile should be laid to the top at one time and the top ridge should be built immediately. After the excavation of the top sill, cohesive soil with a thickness of 30 ~ 40 cm should be backfilled and compacted in layers immediately, especially in the extremely fine sand and silty river sections, mainly to prevent the surface rainwater from flowing down after the pit erosion and endangering the stability or flatness of the slope; When geotextile is used as the filter layer of slope protection, it is not suitable to pour concrete blocks on site. This is mainly because it is difficult to ensure the quality of large-scale concrete pouring on site, and the cement slurry is easy to block the pores of geotextile, which affects its drainage performance, and it is also difficult to repair the damaged parts in the future navigation use.

It should be noted that, according to the physical model test of the waterproof and revetment project of Sunan Canal jointly conducted by Jiangsu Transportation Planning and Design Institute and nanjing hydraulic research institute, the critical stable thickness of the concrete block of the facing is only 4cm, and the actual thickness of the concrete block is 7-9 cm. First of all, considering the sudden rise and fall of the water level when the ship is sailing, the water in the bank slope can not be discharged in time, which has an adverse effect on the concrete block for the surface protection. Therefore, it is necessary to consider a certain safety factor and increase its thickness to 7cm (from the aspect of strength, the safety factor of crack resistance when the thickness is 7cm is1.31); Second, it is common that many ships don't berth at the designated position (anchorage) according to the regulations, but berth in the channel at will. This phenomenon may be difficult to eliminate in a certain period of time, so it is necessary to increase the thickness of concrete blocks to improve their anti-collision ability and avoid concrete blocks from being damaged in use as much as possible (see figure 1).

4.2 Faber slope protection

Because of the wide river surface in the rural section of Luoshe, Wuxi, if the conventional concrete block slope protection scheme is adopted, it is necessary to fill the cofferdam before construction. In order to reduce the influence of cofferdam construction on the safe navigation of ships, combined with the terrain and soil conditions in this section, it is planned to adopt Fab slope protection structure, without cofferdam, and directly pour concrete on the slope. Figure 1 Application of nonwoven geotextile in Danyang Lingkou Waterway. The crest elevation of this section is generally between 5.2-5.7m, the soil quality is 0.5m in addition to the surface layer, and the riverbed bottom is yellowish gray or grayish yellow clay or loam, and its main physical and mechanical indexes are the upper limit. After the overall stability of the bank slope is calculated, 1: 2 can be used under water and 1:2 can be used on water. Woven geotextile bags are used as flexible formwork for concrete pouring. The mould bag is woven from high-strength chemical fiber filaments, and the flexible woven mould bag can fully adapt to the terrain conditions and ensure the pouring of concrete from bottom to top, which is suitable for above-water and underwater construction without pouring cofferdam. In addition, before the filler reaches the design strength, the surface layer of the mold bag can play a transitional protection role for the changes of water flow and wind waves. What should be paid attention to in the construction is: (1) The geotextile bags are longitudinally sectioned for joint, capping and footing treatment. Due to the low water flow speed of the waterway and the good soil quality and low height of this section, the sectioned formwork bags are overlapped, and the geotextile with a width of 0.4m is pressed down, and underwater groove cleaning, deep trench excavation and footing fixation are carried out at the footing; To prevent rainwater leakage or other possible mechanical displacement, the top should be pressurized (width ≥0.5m). (2) Slope protection drainage holes shall be set at the elevation of 3.6m on the slope, and the drainage hole construction shall be carried out simultaneously with the high-pressure sprinkler irrigation concrete with mould bags, and the drainage plastic pipes shall be filled with chemical fiber permeable materials. Pump truck is used to spray 15 pebble (melon seeds) concrete in the mould bag from bottom to top, and the slump is 15 ~ 20 cm.

The geotextile bag slope protection structure has the characteristics of less land occupation and less earthwork excavation. As far as ship collision is concerned, it has stronger anti-destruction ability than slope concrete block slope protection, reduces the construction cost of cofferdam and is beneficial to navigation safety during construction. The comprehensive cost is less 10% ~ 15% than that of masonry revetment (see Figure 2).

4.3 Gravity revetment with slurry block stone

Generally, it consists of three parts: concrete coping, slurry block stone wall and stone concrete floor. No.20 concrete capping beam usually has a width of 0.5~0.6m and a thickness of 0.3, 10. 10 masonry wall should not use wind fossils or smooth pebbles. Mortar or concrete filler shall be dense and seamless, and it is not allowed to directly lap stones. 15 block stone concrete floor is generally 0.5~0.7m thick, and some of them have front toes or rear toes to meet the anti-skid requirements. Layout of geotextile bag in longitudinal section. Special attention should be paid to the drainage of foundation pit during the whole revetment construction to ensure the stability of foundation pit slope and dry land construction. For silty sand or loam mixed with silty sand, light well point drainage must be adopted to reduce the groundwater level. In addition, the backfill behind the wall can only be carried out when the strength of the wall slurry block stone reaches more than 70%. Backfill soil must be backfilled by layers and compacted by layers, and the thickness of layers shall not exceed 0.3m Manual or mechanical compaction can be adopted, and the compaction at corners should be paid attention to. The dry capacity of backfill soil should be controlled above 15kN/m3.

4.4 Heavy revetment with pulp block and stone scale

The counterweight revetment is also composed of three parts: concrete capping beam, mortar block stone wall and stone concrete floor, except that a platform is set in the middle of the back of the wall, and then it slopes back to the basement, thus forming an unloading plate, which can reduce the earth pressure behind the wall and reduce the cross section of the wall. This requires that the soil quality of the foundation pit is good and the bearing capacity of the foundation is large, reaching above 150kPa.

Take the pulp block stone revetment in Xin 'an Town, Wuxi as an example, as shown in Figure 3.

4.5 Treatment measures for soft foundation of revetment foundation

There are soft soil layers with different local thicknesses under the revetment foundation of Sunan Canal. According to the height of revetment and geological conditions in different places, different soft foundation treatment schemes are adopted after demonstration. Fig. 3 Structural schematic diagram of counterweight revetment (1) Usually, the soft soil layer is thin, and the thickness under the foundation is within the range of 1 ~ 2m. It is the most economical and reasonable treatment measure to dig out the soft soil and throw stones, and expand the foundation with the riprap bed to strengthen the foundation.

(2) The height of revetment wall in Changzhou, Wuxi and other areas is in the range of 4 ~ 5m, and the thickness of muddy clay or loam under the foundation is in the range of 3 ~ 8m. The bearing capacity of composite foundation strengthened by vibro-replacement gravel pile can reach more than 135kPa.

(3) In the reach of Danyang City, Zhenjiang, a bank protection foundation with a length of 1500m falls on muddy loam. The maximum thickness of soil layer is 10.85m, the maximum water content is 42.9%, and the bearing capacity of foundation is only 60 ~ 70 kPa. When considering the soft foundation treatment scheme, considering the dense houses in Danyang city, the narrow working surface of foundation pit excavation, the difficulty in material supply if a large amount of light cinder is backfilled behind the wall, and the comprehensive cost comparison, the diameter is finally selected. 50cm dry jet grouting pile to strengthen foundation. The revetment foundation is treated by powder jet grouting pile to form a composite foundation. Due to the improvement of shear strength of composite foundation, the original most unfavorable sliding surface of bank slope will be changed, thus increasing the overall stability of bank slope, and its safety factor can be increased by about 20%. At the same time, the earthwork excavation and concrete floor pouring of revetment foundation pit were changed from wetland construction to dry construction, which not only improved the foundation bearing capacity, but also greatly reduced the construction difficulty and ensured the construction quality.

Attention should be paid to the construction of cement injection pile to strengthen foundation: because the mixing pile is built to the top, because the overlying soil pressure is small and the mixing quality is poor, the top must be dug 50cm to ensure the strength of the pile body; In addition, gravel cushion should be set under the concrete floor to avoid the phenomenon of "void" caused by poor leveling of the top surface and improve the combination conditions of foundation and composite foundation; Secondly, because the top of the pile penetrates into the cushion, the pile force diffuses in the cushion, thus reducing the stress concentration of the pile on the bottom plate (see Figure 4).

(4) In the south section of Lisanqiao Bridge in Wujiang City, Suzhou, the topsoil is about 0.5m, and the thickness under it is 2 ~ 2? 3.5m loam layer, the lower part of which is gray silt, contains a large number of saprophytes, and some of which are sandwiched with fine sand peat layer, with water content as high as 76%. It is in a flow plastic state under high compression, and its allowable bearing capacity is only 30 ~ 50 kPa. In order to ensure the safety of bank protection and save investment, three soft foundation treatment schemes are tested, each of which is 30m. One is to reinforce the foundation with small piles (see Figure 5). The small pile is 3.5m long, with a pile tip diameter of 12cm and a plane layout of 50×50cm. The second scheme is to add geogrids on the stone foundation bed (see Figure 6). The foundation bed is over-excavated by 0.8 ~ 1.0m, and a layer of geotextile grid is laid at the bottom and middle of the stone foundation bed, with the upper layer of stone and the lower layer of gravel cushion. Third, the plan of paving stone bed with woven geotextile. The foundation bed is overbreak1.0 ~1.65,438+0m. First, 3 0cm thick medium-coarse sand is paved, then geotextile is paved, and then gravel blocks are paved. Fig. 4 Structure diagram of revetment (unit: mm) Fig. 5 carries out settlement deformation test on three test sections of revetment foundation with small stakes to test the most unfavorable working conditions during construction. It is found that the walls of the three schemes have not changed, and the settlement after 14 days is only 1 ~ 2cm. After one year of use, the wall is not deformed (the accumulated water in front of the wall has been removed according to the design requirements).

Through joint research and demonstration, it is considered that the above three soft foundation treatment schemes are technically feasible and the cost is not much different. However, the small wooden stake reinforcement scheme does not require overbreak under the foundation, so the construction difficulty is small, and the construction of wooden stakes is convenient and fast. The local construction team has mature experience, so it is decided to adopt the small wooden stake reinforcement scheme, which is widely used in soft soil sections of Wujiang City. Judging from the current operation, the effect is good. Fig. 6 Application of geogrid in revetment foundation Conclusion On the premise of meeting waterway requirements, saving investment and facilitating construction, the revetment project of Sunan Canal has various forms and types according to local conditions, which has accumulated mature experience and achievements for the revetment project of inland waterway.