水泥粉喷桩在地基处理中的应用（Application of cement powder spraying pile in foundation treatment）.doc

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1、【精品文档】如有侵权，请联系网站删除，仅供学习与交流水泥粉喷桩在地基处理中的应用（Application of cement powder spraying pile in foundation treatment）.精品文档.水泥粉喷桩在地基处理中的应用（Application of cement powder spraying pile in foundation treatment）Cement powder spray pile in foundation treatment using 2009-4-10 16:26:00 source: Global Online Channel:

2、 Structural EngineerAbstract: in civil engineering construction, often encountered bad geological conditions, it is necessary to deal with it, in order to meet the requirements of the structure of the foundation. There are many kinds of ground treatment methods 1, in which cement powder injection pi

3、le foundation has been widely used in recent years.Key words: cement injection pile; foundation; application1. Brief introduction of powder injection pilePile are learning the introduction of foreign high pressure jet grouting pile based on the innovation and development of the new type of pile, our

4、 own innovation and the development of complete sets of construction equipment and technology, advantages of this kind of pile can be improved: strengthening foundation, improve the bearing capacity of Foundation (2-3 times) and the stability of the water, no pollution to the environment, no noise,

5、no influence on adjacent buildings, equipment simple hydraulic control technology is easy to grasp, a pile of high efficiency (8m long piles, each pile machine can be completed every day 100), the cost of reinforcement is lower than the construction cost of pile pile for low 40%. 7 layer below and c

6、ohesive soil in groundwater or soil water content more than 25% sand, soft soil, silt soil in the shallow layer (deep 14m) pile reinforcement, but this is not applicable to miscellaneous (MSW) (the foundation bearing capacity is not uniform and soil) The water content is not less than 23%, otherwise

7、 it will cause the pile to be loose.2, engineering examples2.1, engineering works for the South yanchangbu Street commercial building, the foundation excavation part after the emergence of a large number of silt soil, soil depth and small thickness of 3.5 meters, the Geological Exploration Departmen

8、t of the construction site of the evaluation is: the venue for the soft site, belonging to three types of soil, ground water level of 0.9 meters below the surface.2.2, the foundation treatment requirements of the building features is the large upper load, and the soil is weak; basic form of resident

9、ial building drawings for raft foundation requirements 150kPa value for the bearing capacity of the foundation, not up to the value of 110kpa bearing standard test foundation construction site foundation bearing capacity; allowable settlement is less than 200mm; the owners required to reduce the cos

10、t of foundation treatment as much as possible.2.3, treatment options, Nanpu district on this kind of foundation often use prefabricated pile or cast-in-place pile, the survey unit also suggested the use of cast-in-place pile, the project department to make the foundation treatment scheme. After Part

11、y A, design, supervision, construction and management departments of the various arguments, research and comparison of the cost of the program shows that the final selection of our ground treatment program. It is applicable to reinforce the soil with cement injection pile. The mixing pile is more ec

12、onomical than the cast-in-place pile and has less influence on the surrounding environment.2.4. Design and design of composite foundation of powder injection pile, effective pile length L=5.5m, pile diameter 0.5m, plus solid chamber compressive strength is 2Mpa (through laboratory test to determine

13、cement mixing ratio is 15%). From the literature 1 (9.2.2-2), (9.2.2 - 3) calculate the bearing capacity of a single pile Rke=140KN; according to (9.2.2-1) formula can be calculated: the replacement rate of residential buildings m=0.3, according to the layout of the pile, the pile used in rectangula

14、r form.2.5, construction methods, spraying the use of curing agent for P.O32.5 ordinary portland cement, the use of domestic PH-5A type powder injection pile machine construction.(1) the site shall be leveled before the construction, the pile location shall be determined and numbered, and the assemb

15、ling frame shall be provided with a powder injection pile machine to check whether the main engine and other systems are working properly.(2) according to the layout plan of pile location, row number of pile and construction flow section, the moving mixing main machine aims at the design pile positi

16、on.(3) turn on the mixer after drilling into the 50cm, while drilling with the jet, pay attention to prevent the clogging of the powder injection hole, with the drill pipe drilling, reinforcement soil in situ stirring, chopping, drilling to the design depth, stop drilling.(4) when the drill pipe is

17、drilled to the design depth, it rotates backward, starts the cement transmitting device, raises the side of the drill pipe to stir, and the hoisting speed should be less than 1m/min, and the forced powder is stirred with the soil in situ. When the drill is raised to about 2m of the top of the pile,

18、the hoisting speed should be reduced. Lift to more than the design height of 30-50cm, turn off the cement transmission device, the rig rotates in situ, 1min, continue to ascend to the ground. Dusting Pile requires one go, without interruption, jet pressure control in 0.5-0.8N/MM2. in order to improv

19、e the strength of the pile and the bearing capacity, to avoid uneven mixing, then was stirred 1 times in the original pile length, the pile body is completed.2.6, to ensure the strength and integrity of the pile, the key lies in the amount of powder control and mixing is even, in view of this situat

20、ion, the construction of the following measures taken.(1) adopt one spray four stirs craft, its process is as follows. Measuring unreeling machine in place pile drilling in the end (jet) - boot - top (powder) - reverse lifting forward repuddling end - reversal (jet) - to enhance the displacement of

21、pile machine.(2) in the formal construction before choosing a certain number of pile test, to determine the pile construction technique for the parameters in the engineering geological conditions (pile machine drilling speed, stirring speed and enhance the jet mixing speed, scraping speed and spray

22、dust stirred to enhance the speed of the air compressor, air pressure and air volume etc.).(3) the control of pile position deviation is not greater than 5cm, pile verticality deviation is less than 1.5%, the diameter of the pile deviation 4%, pile length deviation of 50mm per meter cement injection

23、 quantity and the design value deviation of 3%.(4) take 24h Quality Supervision Inspection valet service industry, focus on examination of the spray volume per meter, pile length, pile and pile drilling machine verticality and lifting speed, in addition, the use of electronic scales (metering device

24、) to control the spray volume of each pile, and each meter record of a dusting. In order to accurately track the piles from bottom to top quality, once at a depth of gray shortage or broken ash, can accurately fill spray.(5) if drilling, plugging or mechanical failure occurs during drilling or dusti

25、ng, the drilling shall be stopped immediately and the drilling and re drilling shall be carried out after completion of the treatment.(6) cement must be checked and qualified before use.2.7, pile quality inspection, this project altogether hits hits the cement powder spraying pile 13587, the total e

26、xtension 118880 meters. After the owners agree, the following 4 kinds of pile testing method.(1) cone penetration test: the strength test of pile body is carried out with light dynamic penetration test in 7d after completion of pile, the number of inspection is 2%, and the pile is found to be treate

27、d in time. A total of 280 piles were detected, and 20 piles were found.(2) pile head excavation: pile 7d, 2% piles, about 60cm deep excavation,Check the diameter of the pile body, the border of the pile body, the homogeneity of lime soil mixing and the compactness of the pile body. 250 piles were te

28、sted, and the shape of the pile body was in good condition.(3) drilling core compression test: after the pile is 28d, 6 piles are taken for core inspection, and the compressive strength and shear strength of the pile are measured by sampling and maintenance. Test results show that the pile has reach

29、ed the design depth, good shape, the coring rate greater than 75%; the compressive strength of the pile is about 3.1 4.6Mpa, cohesion 1.9Mpa and internal friction solution which is 22.1 degrees, are to meet the design requirements.(4): 28d load test pile selected 4 groups of single pile composite fo

30、undation loading test, according to the technical code for ground treatment of buildings (JGJ79 - 91) test methods specified, determine the residential building of DJM pile composite foundation bearing capacity of FK is larger than 180kpa, meet the design requirements. With the increase of age, the

31、bearing capacity of the foundation still increases to a certain extent.2.8, effect evaluation, this project adopts cement injection pile to deal with weak foundation, and the bearing capacity of foundation increases from 110kpa to 180 200KPa, and the strength increases about 1 times. Since the build

32、ing has been completed and accepted for three years, no uneven settlement of foundation and cracks in the upper structure have been found, and the reinforcement effect is good. The project has been awarded high quality project in Nanpu development zone.By adopting the scheme, the utility model has t

33、he advantages of simple equipment, convenient construction, fast speed, no vibration, no pollution, etc., and the cost is low, and the cost is reduced by 40%. by using the cast-in-place pile, and the cost is saved by 400 thousand yuan for the first party.3, pay attention to the problem3.1, spraying

34、pile is not the pile foundation, the powder spraying pile can be called the foundation pile, but it is not exactly the same as the foundation pile in the pile foundation. The specific differences between the two are as follows.(1) materials are different. The powder jet pile is formed by the indurat

35、ion between the cementitious material and the undisturbed soil and natural water, and the coarse aggregate is not added in the base.(2) the strength is different. Because of the difference of composition materials, the strength of powder jet pile is lower.(3) the bearing properties are different. Th

36、e pile in the pile foundation is a rigid pile, which directly bears the main structure load of the building. The powder jet pile produces a certain compressive deformation when it is compressed, so it belongs to a plastic pile, acting with the soil between the piles, and indirectly bearing the main

37、structure load through the building foundation.(4) the decisive factors of bearing capacity of single pile are different. The factors that determine the bearing capacity of cement pile are the strength of the pile except the support constraint of the soil.(5) determine the strength of specimens at t

38、he age of standard strength; the standard strength of the powder injection pile shall be the strength of specimens at 90d age.3.2, the soil in composite foundation can not be ignored. The powder jet pile is a part of the foundation, and the composite foundation is combined with the foundation soil t

39、o bear the upper load. Therefore, the soil in composite foundation can not be neglected in pile design and pile inspection. When carrying out the test on the foundation treated with the powder jet pile, the static load test of the composite foundation should be carried out, but not the bearing capac

40、ity test of the single pile.3.3, the bearing capacity of composite foundation should be treated differently, and the bearing capacity of composite foundation is generally determined according to the sum of the soil bearing capacity between single pile and pile. The bearing capacity of composite foun

41、dation is not simply added to the bearing capacity of a single pile, but is treated differently according to the soil condition of the pile. When the pile body and the pile bottom are in good soil layer, the composite foundation has a smaller settlement under certain load,The powder jet pile takes m

42、ost of the load. Because of the compressibility, the soil between the piles can only exert part of the bearing capacity. On the other hand, when the jet grouting pile is in the weak stratum and the settlement of the foundation is large, the bearing capacity of the soil between the piles can be fully utilized.