High Pressure Jet Grouting in Deep Water of low pi

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High Pressure Jet Grouting in Deep Water of low pile platform Construction

Abstract: Bengbu Huaihe River Highway Bridge, Chaoyang Road, the main pier in hard water, clay and sand, sandy loam layer, the use of single-wall steel pile cofferdam with high pressure jet successfully completed the construction of low pile platform in deep water,[link widoczny dla zalogowanych], so that high pressure spray pile application has been further developed, but also created a deep low-pile cap construction of new engineering methods, is a term worthy of promotion and application of new technologies. Keywords: rotating pile of low pile platform applications 1, Introduction deep pile cap construction of low-conventional methods generally use a single, double-wall steel cofferdam sink to the back after the construction of concrete elevation, and for the Bengbu Huaihe River Highway Bridge, Chaoyang Road, the main pier surface geology for the hard clay bed, and fell on the base cap permeable sand and sandy loam layer, subject the cofferdam sink to the design elevation becomes complex and difficult. Shore with a high pressure jet grouting pile dike is not only a pool of water and can support the principles, boldly applied to deep water, so that high-pressure jet grouting pile cofferdam and organically integrated, not only solve the Cofferdam through thick hard clay level of difficulty, but also to overcome the sand pile cap excavation, sub-sand layer sealing, supporting the problem. This article focuses on the vertical high-pressure Jet Grouting curtain sealing, the low support in the deep pile cap construction applications. 2, Project Overview Chaoyang Road, Bengbu Huaihe River Huaihe River Highway Bridge is a road across the bridge a total length of 1730m, dual four-lane, 140m main span prestressed concrete with rigid frame, among the main pier is located in the Huaihe River, the basis of embedded rock pillar with 14φ2.0m bored pile, low pile platform, the construction depth of 4 ~ 6m, the structure shown in Fig. (1) Engineering Geology river side of the pier from top to bottom geology were: (a) a hard clay layer: Capacity 260Kpa , slice thickness 2 ~ 4m, the limit friction 60Kpa. (b) sandy loam, sand: cofferdam 2 / 3 weeks strengths for the sand, and its capacity 80Kpa. thickness of 2.2m. the rest is sandy loam layer was soft-plastic state, the average thickness of 1.5m, 13 SPT blow, capacity 180Kpa. (c) hard plastic sub-clay layer: the average thickness of 5.75m, SPT 13 attack, capacity 220Kpa. (d) The following sub-layers and layers of sand. specific geological layout as shown in Figure (2) groundwater main pier at the Huaihe River water, which are impermeable clay soil exposed layer, only sand, sandy loam layer of porous layer, the permeable layer and constitute a complementary relationship between the Huaihe River water. 2, the construction program (1) cofferdam used bottom section with double-wall steel cofferdam cofferdam, the rest are single-wall steel cofferdam, outside diameter of φ = 26.6m, diameter 25m, high 16m, weight 237t. consider the cofferdam, light weight, using the weight method to overcome the outside pressure borrow enormous friction sinking cofferdam more difficult. According to geological subsidence cofferdam 1.5m ~ 2.0m, and then using high pressure jet grouting pile vertical curtain support, sealing, the cap construction. (2) high pressure jet piles ① pile layout By design, the lateral sub-sand layer along the cofferdam area laid two rows of piles , laid three rows of sand region piles, pile cofferdam from the edge of 0.1m, pile spacing of 501mm, pile length 9.0m, pile diameter 0.7m, pile tip into the hard plastic clay in Asia than 1m, the specific layout shown in Figure II model shown in Figure three, four.

calculated that meet the requirements of its force. ② mechanism of high pressure jet piles rig XPZ-50 single-tube high-pressure jet grouting pile, BWT100/30 high-pressure injection pump machine, when the drill after drill design elevation with high pressure jet machine to a level of security under the nozzle to the bottom of the hole grouting pipe, using high pressure equipment to enable the nozzle to the pressure of the slurry jet 20Mpa out, the impact of cutting the soil and mixing with the soil, with the grouting tube formed by the cylinder rotation and increase the pile, slurry and soil through a series of physical and chemical reaction, solid form pile, so as to achieve support, sealing effect. ③ design requirements High Pressure Jet Grouting curtain parts of sand, sand sub-soil permeability coefficient K ≤ 1x10-7 / s, the compressive strength of pile to take 3Mpa. 4, the construction process (1) process → cited hole drilling rig in place (reaming) to the design of the vertical elevation of the nozzle block → → stirred slurry → jet from the bottom up the top job in the design → washing → shift. (2) the construction sequence first hit 2 to 3 test pile, process and understand the construction of jet effects, and finally to determine the construction parameters. Further rotating pile construction, the construction should be within the pile construction, pile after the construction outside, to ensure that piles and piles can be a good bite, a method should be adopted fight hop, and the interval should be greater than 36 hours. (3) construction parameters pump pressure: 20Mpa nozzle diameter and volume: 2.3mmx1 ~ 2.4mmx1 flow: 37 ~ 40L/min drill pipe increases the speed: clay 30/min sandy soil 15/min rod speed: clay 30r/min sandy soil 15r/min water-cement ratio: 1.1 ~ 1.2 Cement: P 32.5, the amount of cement per meter 125Kg / m additives: sodium chloride 1.5%, triethanolamine 0.03% or 1.5% sodium silicate, sodium silicate modulus of 2.4 to 3.4, the concentration of 30 to 40 Baume degrees. Note: triethanolamine and water glass can not be shared, otherwise they will react. 5, Summary 2001 年 8 months to September, Chaoyang Road in Bengbu Huaihe Bridge use the main pier for the first time and achieved good results, through the pile cap excavation to Look, support, sealing meet the design requirements, pile cap excavation dug into the water by the general artificial excavation, not only significant savings in time (5000m3 land in just 15 days), and solve the cofferdam in the hard the difficulty of sinking clay layer, the same type of structure in the future construction, cofferdam design can still be optimized in order to create a better economic efficiency, is a new technology should be promoted. But the fly in the ointment is that rotating pile construction, pile the vertical degree of accuracy must be controlled to within 1 ‰, Guiding Hole hole error is less than 5cm, in order to ensure that pile of bite, otherwise it would cause water seepage, to the construction control zone to difficulty.