What are the requirements for the control depth of the hole formation of cast in place piles?

1) Friction piles. Friction piles.

The depth of the hole is controlled by the design pile length. When the hammer sinking pipe method is used to form holes, the depth of pile pipe into the soil is mainly controlled by elevation and penetration.

Supplement. (2) End-bearing pile. The end-bearing friction pile must ensure that the design pile length and the pile end enter the bearing layer.

Depth. When drilling (punching) and excavation are used to form holes, it is necessary to ensure that the pile holes enter the depth of the design bearing layer; When the hammer immersed tube method is used to form a hole, the depth control of the immersed tube is mainly based on the penetration degree, supplemented by the design of the bearing layer elevation.

You can refer to the "Technical Specifications for the Construction of Highway Bridges and Culverts":

Advantages of using pile foundations:

Good anti-** performance. The static characteristics of the pile are mainly studied by its strength and settlement, and the seismic performance of the pile is mainly determined by its stiffness and stability.

The settlement of the pile is small and the bearing capacity is high, and the settlement of the pile is composed of three parts, and the pile body is elastically compressed; The frictional resistance of the pile side is transmitted downward, which causes the shear deformation of the soil on the pile side and the compression deformation of the soil at the pile end.

It is possible to solve the bearing capacity of special foundation soils.

The construction noise is low, and it is suitable for urban renovation and densely populated sites.

However, the hole formation of cast-in-place pile is completed under the ground or underwater at the pile position, and the construction process is many, and the quality control is difficult, and serious defects such as broken pile are easy to occur if you are not careful. According to statistics, the accident rate of bored piles at home and abroad is as high as 5 10%. Therefore, the quality inspection of cast-in-place piles is particularly important.

The quality of cast-in-place piles usually exists in two.

The methods of cast-in-place pile hole formation are: dry operation hole formation, mud wall protection hole formation, casing hole formation, and manual digging hole.

1. Dry operation into holes.

It is suitable for clayey soil, silt, fill, sandy soil above medium compactness, and weathered rock formations above the groundwater level.

2. Mud wall protection into holes.

1) Rotary drilling rig into holes.

It is suitable for soft and hard soil layers with high groundwater level, such as silt, clayey soil, sand, soft rock layer, etc.

2) Submersible drilling rig into holes.

It is suitable for soft and hard soil layers with high groundwater level, such as silt, silty soil, and sand and pebbles.

3) Percussion drilling into holes.

It is suitable for application in loess, cohesive soil or silty clay and artificial miscellaneous fill layer.

3. The casing is made into a hole.

1) Vibrating immersed tube hole formation is suitable for use in general cohesive soil, silt, silty soil, silt and backfill soil.

2) Hammer sinking tube hole formation is suitable for use in cohesive soil, silt, silty soil, and miscellaneous fill soil layer.

4. Manual hollowing out.

It is suitable for clay with no groundwater or less groundwater, silty clay, clay layer with a small amount of sand, sand pebbles, and ginger stones.

The basic characteristics of bored pile hole construction:

1. Compared with the hammering method sunk into the pile, the construction noise and vibration are much smaller.

2. It can build piles that are much larger than the diameter of prefabricated piles.

3. It can be used on all kinds of foundations.

4. The quality of construction has a great impact on the bearing capacity of the pile.

5. Because the concrete is poured in muddy water, the quality of the concrete is difficult to control.

6. It is labor-intensive and time-consuming, the hole forming speed is slow, and the mud slag pollutes the environment.

Cast-in-place piles are different according to the method of hole formation, what are the forms.

Cast-in-place piles are different according to the method of forming holes, what are the forms of pro! Hello, I am glad to answer for you<> according to the different methods of hole formation, what are the forms as follows: cast-in-place piles according to their different hole forming methods, can be divided into bored piles, immersed pipe piles, artificial digging piles, burst expansion piles four kinds.

1. Drilling and perfusion. Refers to a pile made by drilling a hole in a pile and pouring concrete into the hole (or hoisting a reinforcement cage in the hole first). According to whether the drill bit of the drilling machinery is constructed in the aquifer of the soil, it is divided into three methods: mud wall protection hole formation, dry operation hole formation and casing wall protection.

2. Immersed tube perfusion. It refers to the pile formed by using the hammer piling method or vibrating piling method, sinking the steel casing with a flap pile tip or prefabricated reinforced concrete pile shoe into the soil, and then pouring concrete (or putting a steel cage in the pipe first), and pulling the pipe while hammering or vibrating. The former is called a hammered immersed tube pile, and the latter is called a vibrating immersed tube pile.

3. Manual digging holes. Refers to the pile hole is formed by manual excavation method, and then the reinforcement cage is placed, and the pile made of concrete is poured. In order to ensure the safety of the construction process of manually dug piles, it is necessary to consider the prevention of hole wall collapse and quicksand phenomenon during construction, and formulate reasonable wall protection measures.

The wall retaining method can adopt cast-in-place concrete retaining wall, shotcrete retaining wall, brick masonry retaining wall, caisson retaining wall, steel casing retaining wall, section steel or wood sheet pile tool retaining wall, etc. Taking the widely used cast-in-situ concrete segmented wall as an example to illustrate the construction process of manually dug piles. 4. Burst and expand cast-in-place piles.

It refers to the expansion of the hole with drilling and blasting, putting explosives at the bottom of the hole, then pouring an appropriate amount of concrete, and then detonating to form an enlarged head at the bottom of the hole, and then putting in the reinforcement cage and pouring the concrete of the pile body. Hope mine can help you <>

Do you have any other questions?

<> core drilling method The core drilling method is mainly to use a drilling machine (generally with 10mm inner diameter) to carry out core pulling and hole family judgment on the pile foundation, according to the core sample, the length of the pile foundation, the strength of concrete, and the thickness of the sediment at the bottom of the pile can be determined.

Low strain method The low strain detection method uses a small hammer to hit the panicle grip at the top of the pile, receives the stress wave signal from the pile through the sensor bonded to the pile top, and uses the stress wave theory to study the dynamic response of the pile-soil system.

3.High strain method High strain detection method is a method to detect the integrity of pile foundation and the vertical bearing capacity of a single pile, and the method of acceptance and modification is to use a hammer weight of more than 10% of the weight of the pile or the vertical bearing capacity of a single pile.

Answer]: a, b

According to the first paragraph of Article 1 of the Technical Code for Building Pile Foundations (JGJ94-2008), friction piles should be controlled by the design pile length to form a hole depth and include a rental degree.

Paragraph B is correct, and paragraph 2 of Article 1 stipulates that the end-bearing pile must ensure that the pile end enters the design depth of the bearing layer.

When the hammer sinking pipe method is used to form a hole, the depth control of the end bearing friction pile pipe into the soil should be mainly based on the elevation, supplemented by the control of the degree of penetration, and the control of the depth of the pile pipe into the soil of the friction end bearing pile pipe is mainly based on the degree of penetration, supplemented by the control of the elevation.

Cast-in-place piles must be made into holes for inspection.

In the construction of cast-in-place piles, the quality of the holes directly affects the quality of the piles after concrete pouring: the small aperture of the pile holes reduces the lateral friction resistance of the piles, the bearing capacity of the pile tip, and the bearing capacity of the whole pile. The expansion of the upper part of the pile hole will lead to the increase of the resistance of the upper side of the pile, while the resistance of the lower side can not be fully exerted, and the concrete pouring amount of the single pile will increase at the same time.

To a certain extent, the deviation of the pile hole changes the vertical bearing force characteristics of the pile, which weakens the effective play of the bearing capacity of the pile. The excessive thickness of the sediment at the bottom of the pile reduces the pile length, and the end bearing capacity of the pile tip is directly affected for the end bearing pile.

<>1) The quality and specifications of cement, sand, stone, water, external admixtures and mixed materials used in pile concrete must meet the requirements of the relevant specifications and be constructed according to the specified mix ratio.

2) After the hole is formed, the hole must be cleaned, the hole diameter, hole depth, hole position and the thickness of the sediment layer must be measured, and the underwater concrete can be poured only after confirming that the requirements of the design or construction technical specifications are met.

3) Underwater concrete should be poured continuously, and it is strictly forbidden to have interlayers and broken piles.

4) The length of the anchor reinforcement embedded in the cushion cap shall not be lower than the minimum anchorage length requirement specified in the design code.

5) Representative piles should be selected for testing with the non-damage method, and piles of important projects or important parts should be tested one by one. When there are regulations in the design or there is doubt about the quality of the pile, the pile should be tested by drilling and core sampling method.

6) After chiseling off the reserved concrete at the pile head, there should be no residual loose concrete at the top of the pile.

Answer]: a, b, c, e

The test point involved in this question is the main reason why the verticality of the bored pile does not meet the requirements of the specification. The main reasons why the verticality of the bored pile does not meet the requirements of the specification are: (1) the site flatness and compactness are poor, the drilling rig collapses and the installation is uneven or the uneven settlement occurs during the drilling process, resulting in the deflection of the borehole; (2) The drill pipe is bent and the gap between the drill pipe joints is too large, resulting in the deviation of the drill hole; (3) The wear of the drill bit wing plate is different, and the force of the drill head is uneven, resulting in deviation from the drilling direction; (4) When encountering the interface of soft and hard soil layers or inclined rock surface in drilling, the drilling pressure is too high and the drill bit is stressed unevenly, resulting in deviation from the drilling direction.