Application of Geogrid Stone Mat and Grass Slope Protection in Revetment of Yangtze River
Abstract: The second tender section of the Yangtze River Channel Improvement Project of the Three Gorges Project in Zhijiang City is a comprehensive improvement and protection project for the bank slope of Sihetun section of Zhijiang City. Through the analysis of the water level, flow velocity, wind and waves and other factors in the Zhijiang section of the Yangtze River, the structure of the secondary slope protection (elevation 40.0~44.5m) was changed from the masonry slope protection to the wholesale fiberglass geogrid stone pad grass planting ecological slope protection, and the changed plan has engineering. Low cost, eco-friendly, and good landscape benefits, while meeting the requirements for the safe operation of the project. It has been proved by practice that the fiberglass geogrid for sale stone pad grass planting slope protection scheme is feasible, and it implements the ecological development of engineering construction and realizes the harmonious coexistence between man and nature.
Keywords: Yangtze River revetment; Zhijiang City; wholesale fiberglass geogrid stone pad grass planting; control points
1. Project Overview
The 2nd tender section of the follow-up work river regulation project of the Three Gorges in Zhijiang City is located in the main city section of Zhijiang City on the north bank of the middle reaches of the Yangtze River. It starts at the No. 0 pile position of the Baijili Dike in Binjiang Park and ends at the exit of Dongguan Canal (station 2+260). The main construction contents of the project are the new 2.26km Yangtze River revetment project. The project is also an important part of the ecological environment infrastructure construction of Zhijiang Riverside Park. At the same time, it is also the first technical barrier for the first time in the middle and lower reaches of the Yangtze River to be used. The good engineering effect provides a new idea and method for the “Three Gorges Follow-up Work on the Yangtze River Channel Improvement Project”.
1.1 Natural conditions
The Yizhi River section is about 60.8km long and is a straight curved river. Flowing through the low hills, it is the zone where the Yangtze River transitions from a mountainous river to an alluvial plain. The river channel mainly consists of bedrock nodes such as Wulong Mountain, Huya Beach, Chengbei River, Yunchi, Baiyang, and Zhicheng.
The floods in the engineering section mainly come from the upper reaches of the Yangtze River, with high water levels appearing frequently and lasting for a long time, and the flood peak flow is large. When the upstream flood encounters the flood of the Dongting Lake water system or is affected by the flooding of the Dongting Lake water system, the high flood level of the river section is more likely to occur. According to statistics from Yichang Station, since 1890, there have been 51 years of warning water level exceeding 53m, with 55.94m being the highest in 1896, 55.73m in 1954, and 55.38m in 1981. Since 1950, Yichang Station has an annual peak flow of more than 60,000 m3/s, which is the largest at 70,800 m3/s on July 18, 1981. After the completion of the Three Gorges Project, the maximum flow rate of the controlled discharge shall not exceed 56,700 m3/s when the flood occurs below 100 years, and the nearshore velocity of the Zhijiang River section shall be below 4 m/s.
The bank slope of this section is mainly composed of Quaternary alluvial (alQ4) fine sand, sandy loam, silty loam, and silty clay, which are single-layer, double-layer and multi-layer structure types.
1.2 Engineering role
After the completion of the Three Gorges Project, the clear water discharge caused the erosion of the river section, causing the current river bank slope to retreat continuously, and the danger of bank collapse frequently occurred. The riverbed of the near-shore riverbed in the main urban area was 2~5m deep, and the bank slope retreated, endangering the dike and Zhijiang Riverside Park is safe. In order to ensure the flood control safety of the dikes in the main urban area of the Zhijiang River and the stability of the river regime, the section of the river dam after the impoundment of the Three Gorges will be guarded. The main function of the project is to eliminate the danger of bank collapse caused by the clear water discharge of the Three Gorges Project and to be an important part of the ecological environment infrastructure construction of Zhijiang Riverside Park.
1.3 The origin of design changes
The original design of the revetment engineering structure is: with the dry water platform as the boundary, the upper part is the two-level slope and the pedestrian walkway, the top of the bank is provided with the drainage ditch and the pressure top, and the dry water platform is the underwater riprap protection foot, and the two grade slopes are adopted. Stonemasonry slope protection. The revetment project is located in the Binjiang Park section of the main urban area of Zhijiang. As a place for people to enjoy the scenery, it should reflect the harmony between man and nature. The project construction should be combined with the environmental transformation to meet the growing material and cultural needs of the people. Although the masonry slope protection effect is better against wind and waves, but the stone material suitable for the masonry slope protection needs to be sorted or secondary artificially deblocked, which increases the control difficulty of construction quality to a certain extent, so that the stone The unevenness between the blocks is difficult, and the cost per unit project is relatively high, and the ecological requirements are not met.
In order to further optimize the design, the modern riverbank revetment project layout should not only have an economical and reasonable slope protection function but also meet the ecological function. The project legal person and the design unit went to the Hankou River Beach, Wuchang River Beach, Yichang River Beach, and other urban revetment site inspections. After investigation and analysis of the Yangtze River water level and flow velocity in the Zhijiang River section, it was decided to use the masonry slope protection and wholesale fiberglass geogrid stone pad greening. The slope protection type combined with grass and slope protection, that is, the part with long water immersion time (below the pedestrian walkway) adopts the anti-wind and wave effect better slurry block stone slope protection type, and the relatively short water immersion time (above the pedestrian walkway) adopts easy plant fiberglass geogrid for sale stone mat for grass growing and slope protection with good landscape effect.
2. Advantages of geogrid stone pad grass protection slope protection
With the development of composite materials research, wholesale fiberglass geogrid has good durability and tensile strength, its specific gravity is 0.9-0.91, the temperature range is -30～140°C, chemical resistance is good, infertility is strong, price low. On the grid stone mat, the soil is covered with 20cm for turf slope protection, which effectively solves the problem that the grille will burn when it encounters open flame or the ambient temperature is higher than 350 °C; it also solves the problem of the theft of the fiberglass geogrid for sale. With the growth and maturity of plants, plants and high quality fiberglass geogrid stone mats have long-term protection and greening effect on the slope. fiberglass geogrid factory price stone mat grass slope can withstand the flow of 4~5m/s flow, and the masonry slope protection, In contrast, the fiberglass geogrid manufacturers stone pad grass protection slope protection has the advantages of low engineering cost and good landscape effect while meeting the safety of the project, which reflects the idea that the ecological environment is the foundation in the project construction.
3. Geogrid stone mat grass protection slope technical indicators
3.1 fiberglass geogrid factory price mat
This time, the two-way high quality fiberglass geogrid is used. The raw material of the wholesale fiberglass geogrid is polypropylene (PP), and the mesh pitch is 61mm*61mm. Its main technical indicators: carbon black content ≧ 2%, unit area quality > 0.33kg / m2, low-temperature resistance bending temperature ≦ -30 ° C, longitudinal and transverse tensile strength ≧ 40KN / m, vertical/horizontal 2% elongation The tensile strength at the time is K14KN/m, the tensile strength at the longitudinal/transverse 5% elongation is K28KN/m, and the vertical/horizontal elongation is ≦15%/13%. The fiberglass geogrid manufacturers are made into a mesh mat with a width of 1 m, a length of 2 m and a height of 0.23 m. The ligating material is high-density polyethylene (PE) plied rope with a diameter of 5 mm, a single rope with a breaking strength of K1.5 KN, and a carbon black content ≧ 2%.
3.2 Filling stone
For the stone filled with fiberglass geogrid for sale stone mat, the pebbles with a particle size of 7.5-15 cm are selected, the wet compressive strength is greater than 50 MPa, the softening coefficient is greater than 0.7, and the density is not less than 2.55 t/m3. It is not allowed to use blocks of strips, strips, sharp corners, etc.; weathered rocks, mudstones, etc. shall not be used as filling stones.
3.3 Soil material
The soil on the stone mat is made of clay and a certain proportion of compound fertilizer or peat fertilizer.
3.4 Grass species
The revetment of the Yangtze River is greatly affected by the erosion and submergence of the water flow. It has high impact resistance and is suitable for large-scale, rapid construction and low price of dikes. It is suitable for the local environmental climate and has a high survival rate in the Zhijiang section of the Yangtze River embankment. Grass species, namely Bermuda grass, commonly known as Bermudagrass, at the same time, in order to increase the green benefits of Chengping, keep the seasons evergreen, and interplant ryegrass. The radish of the Bermudagrass is basically flat in 40 days, and the coverage is 95%. Although it may be submerged underwater for 1 month in the main flood season, the turf will be yellow, but the water can still gradually return to green after the retreat, especially suitable for river revetment.
4. Construction technology of geogrid stone pad grass planting slope protection
The construction process of fiberglass geogrid for sale stone pad grass protection slope protection is: cutting slope → repairing filter ditch, drainage ditch → laying geotextile → making grid stone pad → loading pebble → manual sorting → capping cover → tying → covering soil → planting grass → Stonemasonry intercepting ditch. Construction from the bottom up.
4.1 Cutting slope
After the measuring personnel field staked the open line, the on-site construction personnel immediately piling and pulling the wire on the open line, and then the backhoe excavator was in place for excavation; when approaching the design slope, the on-site construction personnel used the level ruler and the self-made slope ruler to track Verify and check the slope ratio until the design requirements are met.
4.2 Laying geotextile
Before laying the geotextile, first level the flat. For the place where there is too much unevenness, manually lay the geotextile after the flattening, so that the geotextile can be in close contact with the slope, which can make the geotextile in a better state, so as not to affect The quality of the laying of geotextiles.
4.3 Single fiberglass geogrid factory price stone mat production
Cut the mesh around the grid body of the stone cage from the net roll according to the design specification 2m×1m×0.23m; then lay the bottom mesh on the formed slope surface and tie it with polypropylene rope. Then, the lower and side barriers are tied into a cage shape, and the lap joints are manually sutured with polypropylene ropes as required. The stone cages are fixed with special bamboo nails, and the fixing depth is 25 to 30 cm.
4.4 Stone filling
The 7.5~15cm particle pebbles in the stone pad are filled with PC350 long arm excavator. To prevent sliding and deformation, the loading sequence is symmetrical from bottom to top and on both sides. When the thickness reaches 23cm, it is manually leveled and covered with the grille. Covering the surface, the edge is connected with a polypropylene rope to form a whole, and then the connection between the cages is required to be killed. The system spacing is 20-30 cm, and the connecting rope is tied in a “shape”, each node At the end of the fight.
4.5 Grid stone pad covering soil and pressure implementation
The soil and soil materials are evenly pulverized. When paving, the PC350 long arm excavator is used to spread the artificial covering to the stone mat. The paving thickness should be uniform and the surface should be flat. Using the excavator bucket for light compaction, the constructor uses a level gauge and a self-made slope gauge to control the slope ratio. Filling machines shall not be used on grilles that are not covered with packing.
4.6 Planting grass
When the grass is transplanted by the straw cutting method, the grass is cut into 30×30cm and 2～3cm thick boxes and transported to the site. The turf is laid with a dense tiling, and the dense tiling should be connected to each other without leaving an interval. It is required to quickly form a ping. After the slab is laid, the shovel is pressed and fixed with bamboo nails. After the grass is laid, compact and water it in time.
5. Construction quality control points
5.1 Procurement link control
The quality of high quality fiberglass geogrid and turf is the key to the success of the whole project. It is necessary to conduct common market research by the owner, design, supervision, and construction to determine the geosynthetics and turf suppliers that meet the engineering requirements.
5.2 fiberglass geogrid factory price inspection
For each batch of fiberglass geogrid manufacturers, there are material qualification certificates and quality guarantees; before construction, the fiberglass geogrid manufacturers materials entering the site are sampled according to the specifications and design requirements, and the ultimate strength and elongation test are carried out to ensure the materials meet the requirements. Design and construction requirements. The base elevation is re-tested before laying to ensure the elevation of the high quality fiberglass geogrid.
5.3 Acceptance of construction procedures
The construction process of grille stone mat grass slope protection has a total of 5 steps of cutting slope, geotextile laying, grille cage production, and filling, covering planting soil and turf laying, and it must be ensured that the construction process of each road is qualified by inspection and acceptance.
5.4 Construction Process Control
According to the quality standard of the unit engineering quality assessment form, the quality inspection personnel of the construction unit conduct self-inspection, that is, the first inspection, the re-inspection and the final inspection, and the supervision engineer carry out the review.
5.5 Turf survival rate control
The turf needs to be maintained by atomized watering. The water for conservation should be non-toxic and free of water that hinders the growth of the plants. During the curing period, ensure that the turf is not dead and grows normally, ensuring that the landscape requirements are met.
6. Conclusion
The second tender of the follow-up work channel improvement project of the Three Gorges in Zhijiang City has been successfully implemented, and the Yangtze River revetment in Zhijiang City has been completed 2.26km. The high quality fiberglass geogrid stone pad grass planting slope area is more than 24,000 m2. At present, the turf coverage rate reaches 95%, completely eliminating the collapse of the section due to the clear water discharge of the Three Gorges Project, and successfully creating a beautiful in the middle and lower reaches of the Yangtze River. The scenery, combined with the Zhijiang Riverside Park, provides a place for the public to relax and cool. The fiberglass geogrid manufacturers stone pad grass protection slope has achieved the expected effect in the follow-up work river regulation project of the Three Gorges and has a very high promotion value.