Supervision of piles, prefabricated piles, construction works

1. The prefabricated pile is prefabricated first, in the prefabrication process, it has been maintained, and it does not need to be maintained after driving into the soil.

2. There are several reasons for not hitting the design elevation (time:

1) The exploration point is not enough or the exploration data is rough, and the engineering geological situation is unclear, especially the undulating elevation of the bearing layer is unclear, resulting in the design considering the bearing layer or selecting the pile tip elevation is wrong, and sometimes because the design requirements are too strict, it exceeds the capacity of the construction machinery or the concrete strength of the pile.

2) The exploration work is based on points and surfaces, and it is impossible to fully understand the lenses of local hard or soft interlayers, especially under complex engineering geological conditions, and underground obstacles, such as large stones, concrete blocks, etc. When piling construction encounters this situation, it is difficult to meet the construction control standards required by the design.

3) When the new modern sand layer is used as the bearing layer, due to the instability of the structure of the new modern sand layer, the strength of the same layer of soil is very different. However, during the construction of the pile group, the sand layer becomes denser and denser, and finally there is a phenomenon that cannot be sunk.

4) The pile hammer is too small or too large, so that the pile cannot sink or sink beyond the control elevation required by the design.

5) The top of the pile is broken or the pile body is broken, so that the pile cannot continue. Infiltrate. In particular, the pile of the column foundation group is too dense and compacted with each other, and the selection of the application sequence is unreasonable.

Governance Approach. 1) In case of hard interlayer, pile planting method, water injection method or air blowing method can be used for construction.

2) If the pile cannot be driven, the pile hammer with larger energy can be replaced, and the buffer cushion can be thickened.

3) Choose a reasonable piling sequence, especially the column foundation group pile, if the middle pile is driven first, and then the surrounding pile is driven, the pile will be lifted; On the contrary, if the surrounding piles are driven first, and then the middle piles are driven, it is difficult to drive in. For this purpose, the zigzag piling sequence should be chosen, or the sequence of symmetrical piling from the middle to the sides.

4) The principle that the pile hammer should be selected should be based on the principle of low hammer blowing, which is easy to penetrate people and can reduce the damage rate of the pile.

5) Before the pile foundation project is formally implemented, the process test pile should be done to check the rationality of exploration and design, and the load test pile should also be done for major projects to determine whether the design requirements can be met.

3. Pile foundation static load test: After the pile foundation is completed, the pile head is treated, the net slurry is chiseled, leveled, and then the qualified unit is invited to the site for inspection.

4. Materials: It is necessary to review the construction plan of the construction unit (the pile should be a special construction plan), technical disclosure, the qualification certificate of the prefabricated pile, the pile pay-off record, the pile foundation construction record, the test pile or the test record (the test pile must be driven before construction, and the number of wood is not less than 2), the concrete precast pile engineering inspection batch quality acceptance record form, etc. The pile must be accepted by the quality supervision station and each unit before the next sub-project can be carried out.

It is recommended that you read the Harbin "Code for Construction Quality Acceptance of Building Foundation Engineering" GB50202-2002

1.Prefabricated piles do not need to be maintained.

2.There are more cases. It may be that the specified load-bearing capacity has been reached.

Lonely rocks may be encountered. Probably because of the groundwater. What to do.

To be honest, we came out of the same path. The best thing to do is to keep a good record of it. Report to the Superintendent.

Because you're just starting out. I don't know a lot of things. Don't do things that others hate.

3.Static load is commonly known as static load. Build a platform and place a large pile of stones on the measuring pile. The ability to detect its actual working state.

4.Upstairs is right.

Pile sinking method.

1. Drive into the pile (hammer pile).

Driven piles are driven to sink the precast piles into the foundation by hammering (also assisted by high-pressure water jets). This construction method is suitable for the situation that the pile diameter is small (generally below the pile diameter), and the foundation soil is plastic clay soil, sandy soil, silt, fine sand and loose crushed pebble soil.

2. Vibrating pile sinking.

Vibrating pile sinking is to install a high-power vibrating pile driver on the top of the pile, on the one hand, the vibration is used to reduce the resistance of the soil to the pile, and on the other hand, the downward vibration force is used to sink the pile into the soil. This construction method is suitable for plasticity of cohesive soil and sand, and is used for the foundation of sand soil that has a large reduction when the shear strength of the soil is vibrate, and its effect is more obvious.

3. Static pile pressing.

Static pile pressing is to press the prefabricated pile into the soil by the static reaction force provided by hydraulic pressure or pulley block with the help of the self-weight of the pile frame and the pressure on the pile frame. This construction method is suitable for the more homogeneous plastic cohesive soil foundation, and the sand and other harder soil layers are not suitable for use because the pile pressing resistance is too large.

4. Water injection pile sinking.

Water injection pile is suitable for dense sand, gravel soil and gravel soil. Use with caution in clayey soil and near important buildings.

5. Bored and buried piles.

Bored piles are suitable for clay, sand, gravel and thick riverbed covering.

1) The axis and elevation of the pile foundation have been measured, and the pre-inspection procedures have been checked. The control piles of the axis and elevation of the pile foundation should be set up near the construction area and should be properly protected.

2) After dealing with high-altitude and underground obstacles, if it affects the use and safety of adjacent buildings or structures, effective measures should be taken in conjunction with relevant units to deal with them.

3) The site should be rolled and flattened, and the drainage should be smooth to ensure the movement and stability of the pile driver, and if necessary, fill and pave construction measures such as sand and gravel, steel track plates, sleepers, etc., and carry out ground reinforcement.

4) According to the axis, release the pile position line, nail the pile position with a wooden peg or steel bar, and mark it with white ash to facilitate the application.

5) Driving test piles. Before construction, test piles must be driven, and the number of them shall not be less than 2, to determine the degree of penetration and verify whether the piling equipment, construction technology and technical measures are appropriate.

Prefabricated piles according to the construction method usually have:

Hammer sinking pile method, static pile pressing method, vibration method.

The hammer sinking method and the static pile pressing method are the most commonly used.

Common precast pile construction methods: hydrostatic pressure method and hammering method.

Steel sheet pile supervision and control points: pro-steel sheet pile supervision and control points are the acceptance of materials: 1. Acceptance of materials:

Concrete precast piles: factory grid certificate, production license, effective quality sampling report within one year; Steel sheet pile tip: factory certificate, specifications, thickness and size of steel plate should meet the requirements of the design of the simple hand; Welding rods:

Factory certificate. 2. Key points of construction supervision: supervise the construction of the pile, check the verticality of the pile, the depth of the pile, the degree of penetration, and check the welding quality and welding art when the pile is connected.

3. Precautions: Specifications of steel sheet pile tip, welding pile stop time (28 minutes), and final penetration. Piling Sequence:

For dense pile groups, the drive is applied symmetrically from the middle in both directions or to the periphery; When one side is adjacent to a building, the blow is applied from the adjacent building to the other direction. 4. In the review of drawings, it should be noted that the center distance of the pile should meet the following requirements (excerpted from the "Technical Specification for Pile Foundation" JGJ94-94) The number of rows is not less than 3 and the number of piles is not less than 9 friction type extruded prefabricated piles, the center distance of the pile is squeezed prefabricated piles In other cases, the center distance of the pile.

1. Acceptance of materials:

Concrete precast pile: factory certificate, production license, valid quality sampling report within one year;

Steel sheet pile tip: factory certificate, specifications, steel plate thickness and size should meet the design requirements;

Welding rod: factory certificate.

2. Key points of construction supervision:

Supervise the construction of the pile, check the verticality of the pile, the depth of the pile into the soil, the degree of penetration, and check the welding quality and welding process when the pile is connected.

3. Precautions should be taken for the songliang:

Sheet pile tip specifications, welded pile stop time (8 minutes), and final penetration.

Piling sequence: For dense pile groups, the pile is driven symmetrically from the middle in both directions or to the periphery; When one side is adjacent to a building, the other direction is applied from the adjacent building;

4. Attention should be paid to the following in the review of drawings

The center distance of the pile should meet the following requirements (extracted from the "Technical Code for Pile Foundation" JGJ94-94);

The number of rows is not less than 3 large and the number of piles is not less than 9 friction type extruded prefabricated piles, the center distance of the pile The precast pile is imitated in other cases, and the center distance of the pile More about engineering services Procurement of bidding documents** production, improve the bid winning rate, you can click on the bottom of the official website customer service for free consultation.

At this stage, how to carry out the construction of prefabricated piles in construction enterprises, and what are the precautions for the conventional construction process of construction enterprises? The following is the relevant content of the professional construction terminology of the pile sinking sequence of prefabricated piles sorted out by Zhongda Consulting, and the basic situation is as follows:

Prefabricated piles are piles made of various materials and various forms (such as wooden piles, concrete square piles, prestressed concrete pipe piles, steel piles, etc.) made in factories or construction sites, and the piles are driven, pressed or vibrated into the soil with pile sinking equipment. In China's construction field, there are mainly two types of prefabricated piles: concrete prefabricated piles and steel piles.

Construction sequence of prefabricated piles: (Zhongda Consulting takes the construction of hammered sinking piles as an example).

Step 1: Pile hammer selection.

Step 2: Lift into place.

Step 3: Piling.

Step 4: Requirements to be met when entering the pile.

Step 5: Stop the hammer standard for hammering the sinking pile.

Step 6: Piling quality control.

Step 7: Problems and solutions in piling.

Precautions for the construction of precast piles:

1. In terms of the same bearing capacity, the pipe pile is more economical, and the production and construction quality can be relatively guaranteed. It is recommended that pipe piles be used in no other cases.

The prefabricated square pile has a long production period, generally one month; Prestressed pipe piles are generally steam cured, which only takes about a week.

2. Attention should be paid to prefabricated square piles, hammered piles and static piles. **Also distinctly different. Hammered piles are much more expensive than static piles, and the reinforcement of hammered piles is larger than that of static piles.

As for the cost of piling, the static pile driver should be cheaper than the hammer pile driver, so it should be considered comprehensively according to the site conditions.

3. When prefabricating square piles, the pile model and concrete number can be marked, and the pile cap and connection method can be selected by the pile-making unit according to the standard drawing If you want to choose the right one, for example, the 400 group B pile can only use the pile cap A (national standard), but some local standard drawings may allow the pile cap B, so when choosing the pile cap, you must carefully look at the standard drawing to select the standard.

5. It is recommended to use prefabricated square piles when uplift piles, which are easy to check the main reinforcement and cracks, which is very convenient. On the contrary, with prestressed pipe piles, it is difficult to calculate the prestress and cracks during uplift! It won't count!

When the main reinforcement is not enough, it can be changed, and the prefabricated square pile is used in a variety of underground uplift piles, and the effect is very good!

6. Now prestressed pipe pile is very popular, but it has its faults and small wall thickness. Prone to cracks.

7. When calculating the bearing capacity of pipe piles, it is necessary to pay attention to the calculation of the pile end. The new 08 pile foundation specification already has a formula for calculating the open pile end. To be reduced!

In addition, in many places, the pipe pile is used without a pile tip, and the reduction of the bearing capacity of the pile foundation should be considered when designing.

8. The length modulus of the prefabricated square pile can generally be determined by the design, and the length can not be an integer, such as it can; Prestressed pipe piles are generally measured in m.

<> about the construction and supervision and control of cement mixing piles? If you want to know the answer, the following is the relevant content of the construction and supervision and control of cement mixing piles sorted out by Zhongda Consulting, and the basic situation is as follows:

The cement mixing pile treatment soft foundation is to use special mechanical equipment to send the cement slurry into the ground, through the cement slurry and the in-situ foundation soil forced stirring and mixing, so that a series of physical and chemical reactions between the foundation soil and the reinforcing material quickly occur, in the short term, the grout forms a solid and fixed load panicle column, and the soft soil foundation becomes a composite foundation with integrity, water stability and a certain strength of the reinforced soil pile.

The project management department assigns a special person to be responsible for the construction of the cement cement mixing pile, and the construction process of the cement mixing pile is next to the whole process. All construction machinery should be numbered, and the on-site technician, the person in charge of the site, the length of the cement mixing pile, the pile distance, etc., should be made of signs and hung in the obvious place of the drilling rig to ensure that the personnel are in place and the responsibility is assigned to the person.

In order to ensure the quality of the pile end, pile top and pile body of the cement mixing pile, the pile should stay at the bottom of the pile for 30 seconds when the first drilling travel spraying should be carried out, the pile end should be grinded, and the remaining slurry should be sprayed into the pile body during the lifting process, and the pile head should be ground at the top of the pile, and the residence time should be 30 seconds.

The quality of cement mixing pile construction is directly related to the effectiveness of foundation reinforcement, and is further related to the stability of the upper main structure, which is very important for the normal operation of the water supply system project. Therefore, the construction quality of the mixing pile must be controlled in advance, controlled during and tested after the event, and strictly supervised and controlled.

The quality assessment of the cement mixing pile unit project shall be in accordance with the "Water Conservancy and Hydropower Project Cement Mixing Pile Foundation Unit Engineering Quality Assessment Form", which shall be self-assessed by the contractor and recognized by the supervision department, and the unit project shall be assessed.

The pressure grouting method is used to treat the unqualified piles. The low strain detection method cannot be used for the detection of multi-section prefabricated piles with piles, and at the same time, the pile connection method of the national standard 97G361 should be further improved and strengthened under the conditions of large impact force and high number of hits.

For the static pile project, due to the unpredictability of the construction situation, in order to ensure the quality of the project and facilitate the handling of emergency situations, the supervision of the side station personnel should stick to their posts at any time. 1. Working methods: control methods of witnessing, side stationing, patrol and parallel inspection.

2. Work measures: organizational measures, technical measures, economic measures, and contract measures.

1. Before the construction of the pile foundation, the supervisor must review the construction organization design or construction plan of the static pile. In addition, the construction unit must also submit the business license and qualification certificate of the enterprise to the supervision and review. 2. After the prefabricated pipe pile enters the site, the construction unit shall submit the prefabricated pipe pile factory quality certification document to the supervision for review, and the supervision must also conduct on-site inspection of the appearance quality of the pile body, and allow it to be used only after meeting the specifications and design requirements.

The surface color of the pile should be uniform, the depth of the corner should be 10mm, the total area of the honeycomb surface should be 5%, the cross-sectional size should not be greater than 5mm, the flatness deviation of the pile top should be 2mm, and the pile body should be bent by 1 1000L (L is the pile length). 3. Before the start of construction, the pile site must be inspected and accepted by the supervision, and the construction is allowed after passing the inspection.