What is cfg composite foundation

CFG pile is the abbreviation of Cement

Fly-ash

Grave, which means Cement Fly-ash Gravel Pile, a variable strength pile made of crushed stone, stone chips, sand, fly-ash mixed with cement and water, and made by various pile forming machines. By adjusting the cement mixing amount and proportion, its strength grade varies between C5-C25, which is a kind of pile type between rigid and flexible piles.CFG piles and inter-pile soils together, through the bedding layer to form CFG piles composite foundation*** with the work, so it can be based on the composite foundation traits and calculations of engineering design.CFG piles are generally not required to calculate the reinforcement, and also can be utilized as industrial wastes of fly ash and stone chips for the mixing material, further reducing the cost of the pile, which can be used for the construction of the pile. CFG pile-application scope CFG pile has a wide application scope. There are a lot of successful cases in sandy soil, silt, clay, silty soil, miscellaneous fill etc. CFG piles are suitable for independent foundation, strip foundation and raft foundation.CFG Piles-Construction CFG piles construction,

The following construction techniques should be selected according to the site conditions:

Long auger drilled piles,

Applicable to clay, silt, and vegetal fill above the groundwater level, above moderately compact pile soil.

2. Long auger drilling and filling with pumped mixture in pipe,

Suitable for clay, silt and sandy soil,

as well as the sites with strict requirements on noise or mud pollution.

3.Vibratory immersed tube piles,

Suitable for pulverized soil, clayey soil and plain fill foundation.

CFG pile-material requirements 1, concrete, concrete admixtures and mixes:

Retarder, fly ash,

should be in accordance with the corresponding standards,

The amount of mixing should be determined by the laboratory according to the construction requirements.

2, strictly in accordance with the proportion of preparation of the mixture.　　The slump of long auger drilling and in-pipe pumping mix should be 160~200mm,

The slump of vibrating immersed tube piling should be 30~50mm,

The thickness of floating slurry on the top of the pile should not be more than 200mm after the vibrating immersed tube piling.

4.The design depth of the pile should be accurately controlled by the lifting and lifting of the pile after the drilling. After drilling to the designed depth, the time of lifting the drill pipe should be accurately controlled, the pumping amount of mix should be matched with the speed of pulling the pipe, and the pump should not be stopped to wait for the material when encountering saturated sandy or saturated powdery soil layer; the speed of pulling the pipe in immersed pipe casting piles should be controlled according to the uniform speed, and the pulling speed of pulling the pipe should be controlled at around 1.2~1.5m/min, and the pulling speed of pulling the pipe should be slowed down appropriately when encountering silt or silty soil.　　

CFG pile-other precautions 1, the temperature of the manhole of the mixture shall not be lower than 5℃ during winter construction, and the heat preservation measures shall be taken for the pile head and the soil between the piles.　　2. The deviation of verticality of construction shall not be more than 1%; for the foundation of full-row layout pile, the deviation of pile position shall not be more than 0.4 times of the pile diameter; for the strip foundation, the deviation of pile position shall not be more than 0.25 times of the pile diameter, and the deviation of the pile position for the single-row layout pile shall not be more than 60mm. Main technical indexes: According to the actual situation of the project, the commonly used construction process of cement fly ash gravel pile includes long auger drilling, pumping the mix in the pipe to form pile, vibrating, sinking pipe grouting to form pile and long auger drilling. According to the actual situation of the project, the commonly used construction techniques for cemented fly ash rubble piles include long auger drilling, pumping mixture in pipe to form piles, vibrating immersed pipe grouting and long auger drilling and grouting. The main technical indexes are as follows: foundation bearing capacity: design requirement; pile

diameter: 350-600mm; pile

length; design requirement, the holding layer at the pile end should be chosen as the soil layer with relatively high bearing capacity; pile

body

strength: the strength of the concrete meets the design requirement, usually ≥C15; pile

intermediate

pile

strength: the strength of concrete meets the design requirement, usually ≥C15; pile

Inter-pile

distance:

suitable to take 3-5 times the pile diameter; pile verticality: ≤1.5%; bedding

bedding

layer: suitable for sand, coarse sand, gravel or graded gravel, etc., not suitable for pebble, the largest particle size should not be greater than 30mm. thickness of 150-300mm, tamping degree ≤0.5mm, and the thickness of the filling ≤0.5mm, and the thickness of the filling ≤0.5mm. The thickness is 150-300mm, and the degree of tamping and filling is ≤0.9. In the actual project; the above parameters are determined according to the conditions of geological conditions, type of foundation, type of structure, foundation bearing capacity and deformation requirements, or on-site test. Question

Add Abstract

Abstract

CFG

Pile composite foundation is a new foundation treatment technology, this paper introduces

CFG

pile characteristics and current status of engineering applications.

Keywords

CFG

Pile Basic Theory; Characteristics; Engineering Status

Composite foundation is to set up a certain proportion of reinforcing body in the natural foundation, and by the original soil and reinforcing body **** the same to bear the building load transmitted by the foundation, such a kind of artificial foundation is called composite foundation. The reinforcing body is composed of materials whose strength and modulus are higher than those of the original soil, and it is customary to call the reinforcing body a pile. According to the different materials, the longitudinal reinforcement can be divided into crushed stone piles, hydraulic soil piles,

CFG

piles and so on. According to the strength and modulus of the pile body, it can be divided into bulk composite foundation (such as vibrated rubble pile composite foundation), low-bonded strength pile composite foundation (such as lime pile, gray soil pile), medium-bonded strength pile composite foundation

(

such as rammed hydraulic soil pile composite foundation

)

, and high-bonded strength pile composite foundation

(

such as

CFG

pile

)

1

Characteristics of CFG

pile composite foundation

Cement Fly Ash Gravel Pile Method (abbreviated as

CFG

pile) is a method of cement, fly ash, crushed stone, stone chips, or sand mixing and blending with water to form high It is a foundation treatment method that consists of piles, inter-pile soil and bedding layer together to form a composite foundation.

CFG

The backbone material of CFG

pile is crushed stone, coarse aggregate; stone chips are medium-sized aggregate to improve the gradation of the pile body and enhance the strength of the pile body; fly ash is fine aggregate, and has the role of low grade cement, which can make the pile body have obvious late strength. This foundation reinforcement method absorbs the advantages of vibrated rubble pile and cement mixing pile, firstly, the construction process is as simple as ordinary vibrated immersed pipe grouting pile, no site pollution and small vibration influence compared with vibrated rubble pile; secondly, the materials used only need a small amount of cement, which is convenient to get materials locally; saving materials; thirdly, the force characteristics are similar to cement mixing pile.

CFG

CFG

Pile mixing material fly ash is a kind of industrial waste discharged from the combustion power plant, it is ground to a certain fineness of the fly ash in the pulverized coal furnace combustion (

1,100

~

1,500

℃

College of dust collector collection of the fine ash, referred to as dry ash. With the wet method of ash from the fly ash is called wet ash, due to part of the activity of the first hydration, so its activity is also lower than the dry ash, the activity of the fly ash is to affect the strength of the mixture of the main indicators, the higher the activity of the mixture, the less water, the higher the strength; the lower the activity of the mixture, the more water, the lower the strength. Fly ash collected from different power plants, due to the different types of raw coal, combustion conditions, coal fineness, ash collection methods, the activity is very different, so the strength of the mixture has a great impact. The activity of fly ash is determined by the content of various particle sizes

AL

2

O

3

and

SiO

2

, and

CaO

is also favorable to the activity of fly ash. The particle size composition of fly ash is the main indicator of the quality of fly ash, generally the finer the fly ash, the more spherical particles, the increase in hydration and contact interface, it is easy to play the activity of fly ash.

CFG

Pile aggregate crushed stone, mixed with stone chips is to fill the voids of the crushed stone, so that the gradation is good. The contact specific surface area increases and improves the pile shear strength.

CFG

Pile composite foundation is generally suitable for dealing with cohesive soils, silt, sand, artificial fill and silty soil foundation; can be used for both soil with good compacting effect and soil with poor compacting effect. When

CFG

piles are used in soil with good compacting effect, the increase of bearing capacity is both compacting and replacement; when

CFG

piles are used in soil with poor compacting effect, the increase of bearing capacity is only related to replacement. Compared with other pile types for composite foundations,

CFG

piles have a particularly pronounced replacement effect due to the lighter pile material. As far as the foundation form is concerned,

CFG

Pile composite foundation is suitable for both strip foundation (with ground beam) and independent foundation, as well as raft foundation and box foundation.

2

CFG

Pile composite foundation treatment technology status

CFG

Pile composite foundation is a new foundation treatment technology,

CFG

Pile composite foundation experimental research is the Ministry of Construction's "Seventh Five-Year Plan" program.

CFG

Pile composite foundation test research is the "seventh five-year plan" of the Ministry of Construction

,

in 1988

and was applied in the engineering practice,

CFG

Pile composite foundation test research results were appraised in

1992

by the Ministry of Construction

. p>,

experts believe that the results have the international leading level;

CFG

Pile composite foundation complete set of technology,

1994

in 1994

was listed by the Ministry of Construction as the national key promotion project

,1997

was regarded as the national workmanship, and was included in the national industry standard "Technical specification for building At present

,

this technology has been popularized and used in 23

provinces and cities in China

,

according to incomplete statistics

,

there have been

1,000

multiple projects that use this technology,

CFG

is the most important technology for the construction industry in China. CFG

Piles can reduce environmental pollution

,

and achieve the purpose of waste utilization

,

has significant economic and social benefits due to the addition of industrial waste fly ash into the pile body material

,

CFG

Piles are not reinforced.

,

And give full play to the bearing capacity of the soil between the piles

,

Compared with ordinary concrete piles

,

The number of piles needed is less

,

The cost of the piles is only 1/3 of that of the piles,

~

1/2,

Construction cost is also lower.

Engineering cost is also low

,

worthy of focusing on the promotion.

With the promotion and application of

CFG

pile composite foundation throughout the country

,

especially in recent years,

CFG

pile composite foundation technology plays a very important role in China's capital construction, from buildings to roads, coal mines have been commonly used. Especially in recent years, this technology has been applied in the foundation treatment of high-rise buildings in the northern region, and according to incomplete statistics, there are

300

more than 300

high-rise building foundation treatments using

CFG

pile reinforcement technology. Therefore, in recent years, a lot of achievements have been made in the research on various aspects of

CFG

pile composite foundation, (

1

) on the research of

CFG

pile composite foundation engineering characteristics,

Professor Yan Mingli

and Senior Engineer Zhang Donggang have done a lot of experimental work, (

) summarizing its engineering characteristics. summarized its engineering characteristics; (

2

) on the design of

CFG

pile composite foundation, Zhao Qihua and Li Jianguang put forward the design idea of

CFG

pile composite foundation with double control of settlement and bearing capacity; (

3

) on the

3

On the experimental research on the material properties of CFG

piles, Fan Yun and Wang Yingzhen obtained the change rule of the strength of pile material under different proportioning conditions through the indoor proportioning test of CFG

piles, and put forward certain principles and methods that should be followed in the proportioning of CFG

piles; (

4

The design idea of composite foundation is to design CFG

piles.

4

)Regarding the bearing properties of

CFG

pile composite foundation, Zhang Jing, Li Bin and others carried out a large number of experimental studies, analyzed the

CFG

pile composite foundation bearing properties through the results of static loading test after composite foundation treatment of the softer and weaker soil layers in the engineering, and analyzed the different composite foundations such as monopile, pile-soil composite, pile-soil composite, and inter-pile composite foundation, and so on. Different composite foundation test results such as single pile, pile-soil composite, inter-pile soil, etc. were analyzed and compared, and it was concluded that the late strength growth of the

CFG

pile was higher, which was a favorable conclusion for the overall pile properties. (

5

) Regarding the application study of

CFG

pile composite foundation in engineering examples,

Professor Yan Mingli

and Zhang Donggang Gaojiao worked on a large number of application studies of engineering examples, and summarized many engineering experiences. Regarding the research on the deformation, side load conditions and mechanical properties of

CFG

pile composite foundations, many experts have made a lot of research work and come up with the corresponding laws and results, so I won't repeat them here.

Each foundation treatment method has its own geological conditions and scope of use, as well as a specific construction method, and under different conditions, different problems will be encountered, all of which require different treatments.

CFG

Pile composite foundation treatment technology has the characteristics of fast construction speed, short construction period, easy quality control and low project cost, therefore, it has become one of the main foundation treatment technologies in high-rise buildings in Zhengzhou area; however, due to the great difference in the geological conditions in Zhengzhou area, as well as the different surrounding environmental conditions, a lot of different problems have been encountered in the construction in the recent years. However, due to the geological conditions vary greatly in Zhengzhou area and the different surrounding environmental conditions, many different problems have been encountered in the construction in recent years, some of which have led to different degrees of economic losses, which should be emphasized and studied to provide experience for the future projects and to prevent the problems from occurring in the future; the correctness or otherwise of the design and construction methods is related to the safety of the project, the cost of the project, and the length of the construction period. Summarize engineering experience, is to ensure safety, improve quality, shorten the duration, save investment, create quality projects.