The steel sheet pile structure has the advantages of light weight, high strength, close lock, convenient construction and high construction speed. Although the amount of steel is large and the cost is high (when the steel sheet pile is no longer recycled) Deep foundation pit support, the use of sheet piles is still more common, but the use of deep foundation pit excavation is still relatively rare. In 1998, when the reconstruction of Baijian Power Drainage Station in Sanshui District, Foshan City, Guangdong Province, due to the restriction of engineering geological conditions of pumping stations, it was not possible to solve the problems of excavation of foundation pit by taking measures such as light well point drainage and stump slope protection Soil slope collapse problem, the use of steel sheet pile supporting cut-off method and achieved good results, thus ensuring the pump station construction progress and construction quality. First, the project profile Baitu town is located in the southernmost tip of Foshan Sanshui District, west of the West River. Eighty percent of the town's drainage task is undertaken by the two existing drainage stations (Kokli station and Dagang station). However, both of these stations are secondary drainage stations, of which, Founded in 1958, although several technological improvements have been made in recent decades, some fundamental problems, such as various reasons, low design standards and improper drainage planning, have not been solved. In particular, the operation of the pumping station should be restricted by the downstream Guanshan large pumping station, so water drainage can not be normally drained. In order to adapt to the steady and sustained development of the industrial and agricultural production in Baodi Town, it was decided to relocate Liuli Station to rebuild the existing two second-level pumping stations into a first-level drainage station to discharge the waterlogging directly into the Xijiang River. The rebuilt pump station is named Baizhen Drainage Discharge Station, benefiting an area of ​​2800hm2, of which 860hm2 are fishponds. It will be the largest pump station currently installed in Sanshui District. The reconstructed Baijian Power Station is located at the 19 + 200 Stake at Qiaosanglian. The pump station covers a rain area of ​​93km2. It is designed according to the standard design that the rainstorm amount (206.4mm) is drained for 3 days in 10 years and the total drainage flow is 35.42m3 / s. The device 1600ZLQ9.5-8 vertical axial-flow pump 4 Taiwan, with TL1000-20 / 2150 10kV vertical synchronous motor, the total installed capacity of 4 × 1000kW. Do not wait for the pumping station project third class, the main hydraulic structure for the three. The pump house is a block-based structure with side piers all around. The foundation is a combined floor. The bottom elevation is bead base -5.35m. The lower part is prefabricated pipe pile foundation. The elevation of the piling platform is designed to be -3m. Second, the hydrogeological conditions Baicheng town is located in the subtropical, warm climate, abundant rainfall, and most of the rainfall concentrated between April and September, the rest of the month less rainfall. The maximum annual rainfall of 1720.9mm, the minimum 933.8mm, an average of 1475.6mm. The Baijian power station is located at the bank of the left bank of the main stream of the Xijiang River and has a single terrain in the river section. It is mainly controlled by floods of the Xijiang River and the Beijiang River. The impact of the tides is very little and basically belongs to the non-tide area. The section where the pump station is located originally belonged to the alluvial plains of the river facies, the terrain was a staircase, the embankment was a beach platform, and the embankment was a fish pond, paddy field and vegetable land. According to the geological survey report, the geological structure from top to bottom are: artificial fill layer (flood embankment), the Quaternary fluvial sedimentary layer of sedimentary facies, tertiary limestone bedrock. The characteristics of the rock and soil layers from top to bottom: (1) Backfill silty clay, thickness 3.8 ~ 12.4m, for embankment filling, filling more solid, hard and plastic. All the culvert pipes of the pumping station are buried in this layer. After the flood control dike has been solidified for a long time, the filling has been stable, dense and the bearing capacity is also high. (2) Silt, thick 8.0 ~ 20.3m, stable soil, full audience distribution, is the basis of the pump house holding layer, soil hard, plastic, high carrying capacity. (3) fine sand, thickness 17.3 ~ 31.3m, audience distribution, soil loose to slightly dense. (4) silt, thickness 8.4 ~ 8.6m, only found in some strata, saturated and loose. (5) silt silt clay, thick 3.2 ~ 9.6m, widely distributed, saturated, flow plastic to soft plastic. (6) In the weathered limestone, the surface of the rock is uneven, the height difference is large, dense, hard and strong, but the depth is large, generally 38 ~ 45m below the surface. The geomorphic units in the site are simple with little change in soil layers, mostly silty and silty clay, silt and sand but with unequal intensity and low groundwater depth, shallow water depth, high groundwater level and site II Classes and other foundation conditions. Third, the construction of the foundation pit Baizhan electric power station reconstruction project in December 1998 groundbreaking, excavation of foundation pit, fill the cofferdam. After more than 10 days, the excavation of the main pumping station's foundation pit has basically taken shape. The following engineering measures include: piling platform, light well drainage, stake protection, sheet pile support, pit deep well foundation and surface treatment six links. 1. Piling platform according to the design requirements, pile foundation elevation of -3.0m, but when the foundation pit excavation to the design elevation, due to the higher groundwater level, more water, the use of conventional drainage ditches have not been effectively reduced Groundwater level. Because the saturated soil foundation, if any disturbance at this time is likely to become silty fine sand, reduce the bearing capacity, pile driver will not be able to enter the face of the operation. In order to avoid the above problems, it is decided to use the backfill 1m thicker dry clay as the base of piling platform after leveling and rolling so as to ensure the smooth construction of piling construction team. 2. Light Well Drainage Because the soil within the depth of nearly 10m below the excavation surface of the excavation contains silt, poor water permeability, it is very easy to produce quicksand piping, coupled with the vibration generated during the pipe piling, slope collapse more To be serious, the stability of pit slope is extremely unfavorable. In order to keep the piling platform filled from flooding and ensure the smooth progress of the pipe pile construction, after detailed investigation by the relevant experts, using the water pump to clear the drainage method failed to work, we decided to adopt a method of artificially lowering the groundwater level, namely adopting Light well point drainage method. The concrete method is to use the steel pipe and hard plastic pipe to make a hole, and a 6m deep well point is arranged every 3m around the foundation pit, and a total of 40 well points are arranged. Well points using excavator pressure φ150 steel pipe into the hole, and then with a hole φ100 hard plastic pipe wrapped with filter cloth inserted into φ150 steel hole into the well, and poured in the hard plastic pipe around the broken stone. In this way, the water pump can be used to pump the well water into the gullys on both sides of the foundation pit of the pump house, and then the water pump can drain the water from the foundation pit. Facts show that the use of light well point drainage (downhole elevation of about -8m), did reduce the pit water table has played a certain role, to a certain extent, to ensure that the station pipe pile construction. 3. After the completion of the construction of the pile protecting pile, the excavation of the main pumping station pit will be continued. However, because the groundwater level can not be controlled below the effective height, the result is more water in the foundation pit. Due to the large excavation space around the excavation and the left and right sides of the foundation pit and pump house during construction, the excavation is relatively smooth. However, on the side of the Xijiang river that is the water culvert pipe, the slope collapse occurred, which caused the foundation pit excavation to fail keep going. In order to maintain the stability of the slope, we put a row of 6m long wooden piles at a distance of -2.0m and -3.0m on the side of the foundation pit on the culvert side at a distance of 0.5m. Sand package foot. However, when excavation of the foundation pit continues, the tendency of slope cracking and falling still appears and the safety of the foundation of the culvert is threatened. This shows that well point well drainage and piling slope protection still can not fundamentally solve the above problems. 4. Due to the late start time of the pumping station, after more than a month of construction and the foundation pile has been completed for nearly 10 days, the foundation pit of the main pumping station has still not been able to excavate to the founding surface of -5.35m. In order to ensure the construction period, the Engineering Command convened design, supervision and construction units and other departments concerned to jointly discuss and decide to adopt the plan of supporting the steel sheet pile for water cut-off. The result is that it not only plays the role of supporting but also plays the role of impermeability. The concrete approach is to arrange a row of steel sheet piles near the foundation pit slope on the side near the culvert of the water outlet, that is to say, the originally arranged double row of wood piles. The pile position is about 3m from the edge of the bottom of the main pumping station, Both ends of the extension of 5m layout, total length of 32m. The steel sheet piles are of type LSⅢ, each length is 9m, the height of pile top is -1.5m and the height of pile bottom is -10.5m. The top of the steel sheet pile is anchored by 10mm steel wire rope and anchored. Slope slope cut load, in order to reduce the pressure of sheet piles. 5. Deep well dewatering of foundation pit adopts steel sheet piles to solve the problems of foundation pit support and horizontal cutoff seepage, but it still fails to reduce groundwater level and solve the problem of permeation around both sides of steel sheet piles. In order to excavate the excavation pit below -5.35m, the foundation pit water level must be reduced to at least -6.0m elevation to keep the foundation pit dry. Therefore, it is necessary to cut off water seepage from the main supply source of groundwater and the water pressure on both sides of the steel sheet pile Seepage flow. To this end, in addition to the use of steel sheet piles, we also arrange the left and right sides of the main pumping station foundation pit of four uniformly distributed wells, diameter of 127mm, well depth of 12.0m, downhole elevation of -14.0m or so, Using φ127m casing, the bottom of the drainage pipe is also φ127mm casing processing, outsourcing 6 layers of filter cloth, drilling φ146mm hole, hole casing, surrounded by backfill broken stone, the bottom of the seal, with a head of 40m A small pump pumped water from the casing. The water was first pumped to the gutters on both sides of the pit and then out of the foundation pit by a pump. 6. Surface treatment of steel sheet pile supporting cutoff and deep well dewatering, can well maintain the stability of the slope, and effectively reduce the foundation pit of the groundwater level, the excavation of the pit to work smoothly, but digging to the foundation Surface, the foundation pit is still a small amount of piping. To this end, we will over-excavation of the base construction 0.3m, and then backfill 0.3m thick gravel, and the depth direction of the foundation pit are provided drainage ditch, backfill with gravel, spacing of about 4 ~ 5m, depth of about 0.5m, In order to clear the pipe flow; in the middle of the foundation pit and on the side of the forebay foundation pit are provided on both sides of the drainage wells with a diameter of 1m, wells set steel cage, outsourcing filter cloth, surrounded by sand backfilling, mainly for the collection of pit Of the pipe water flow, and then discharged from the foundation pit to keep the foundation pit without water. Backfill of overburden gravel after compaction leveling, but also can increase the strength of the basement. Fourth, the project proved that the practice of steel sheet pile support cut off seepage and pit deep wells to reduce the groundwater level, the foundation pit to dig deeper can quickly dig to a predetermined elevation by the base surface treatment can pour the main pump room the next day Floor of the concrete cushion, thus creating the next phase of the construction of favorable conditions. It is not difficult to see that the construction scheme of steel sheet pile support and deep well dewatering adopted in the late excavation of the foundation pit is feasible and effective and the progress of the project was grabbed back to ensure the smooth progress of the entire project.
Hardening Furnace,Electric Furnace,Spring Quenching Furnace,Induction Hardening Furnace
Changxing Jiacheng Furnace Industry Co. Ltd , https://www.jcfurnace.com