How to control the pile head of concrete cast in place pile

1. According to the design concrete pouring volume (plus the amount of over-pouring concrete), the concrete will generally exceed the square, so the design amount of pouring generally does not reach the design elevation.

2. After the design amount is poured, measure the elevation of the concrete surface with a measuring rope, calculate the amount of concrete with the difference between the design elevation and the measured elevation, and then fill the concrete.

3. When the concrete of the part still does not reach the design elevation, repeat the procedure of the second part, and put the measuring rope into the hole for real-time measurement when the design elevation is about to be reached.

4. The design of the over-filling part is only to ensure the quality of concrete pouring, and it does not have to be very accurate, so it does not matter if it exceeds a little bit and lacks a little bit.

1. Make a mark on the pile driver 2, control the thickness of the protective soil of the pile head 3, and control the filling coefficient "Combined with the geological report, do not use different geology to control the filling coefficient".

First, the construction control points of building cast-in-place piles.

1. The safety distance between the two adjacent piles should be greater than 4d, or the minimum time interval should not be less than 36 hours.

2. The specific gravity of the mud after the second cleaning should be less than, and the thickness of the sediment at the bottom of the hole should meet the regulations

3. After the second hole is cleared, the head height should be maintained in the hole, and the concrete pouring should be completed as soon as possible.

4. When pouring the old god concrete, it is necessary to always take care of the buried depth of the conduit 2-6m, it is strictly forbidden to pull the conduit out of the concrete surface, the reaming coefficient should be controlled, the concrete elevation of the pile body should be controlled at a higher than the designed pile top elevation, and the height of the slurry should be chiseled to ensure that the strength of the exposed pile top concrete reaches the design value.

2. Common quality problems and preventive measures.

1. The steel cage floats.

Reason analysis: a) The spacing between the conduit and the reinforcement cage is small, the particle size of the coarse aggregate is too large, the lap welding head of the reinforcement cage is not welded flat, and the flange hangs the reinforcement cage in the process of lifting and sinking the conduit. (Crude treatment: stop perfusion, repeatedly shake the catheter up and down, or rotate in one direction).

b) In the process of installation and hoisting of the reinforcement cage, the skeleton is twisted, the stirrups are deformed, the conduit is dewelded or the conduit is tilted, so that the reinforcement cage is in close contact with the outer wall of the conduit. (Treatment: Shake the catheter repeatedly and move it up and down to cut the connection between the two.)

c) The concrete is poured too fast, and when the concrete surface rises to the bottom of the reinforcement cage, an upward "buoyant" is generated, resulting in the floating of the reinforcement cage. (Treatment: control the pouring speed).

2. Catheter unplugging:

In the concrete pouring process, the conduit is separated from the concrete surface, and the mud enters the conduit, resulting in pile breakage.

Cause analysis: construction operator error, too much conduit removal, too fast lifting.

Preventive measures: strictly control the lifting speed of the catheter, measure the height of the concrete surface before the catheter is removed, and calculate the number of sections of the catheter removed.

Treatment method: When the catheter is hollowed out, the catheter should be quickly inserted into the concrete, and the mud in the catheter should be pumped out by pumping equipment to continue perfusion.

3. Buried pipe: In the process of concrete pouring, the conduit is buried in the concrete and is not pulled out in time, and the waste pile is formed after the concrete is hardened.

Cause analysis: a) The initial setting time of concrete is short, and the rotten town is too long during the intermittent perfusion time, resulting in the lower concrete has been initially set when re-pouring, and the catheter has not been pulled out.

b) The conduit is hung by a rebar cage.

c) The hole wall collapsed and a large amount of mud buried the conduit.

Treatment method: If the conduit cannot be pulled out, it will generally be treated as a waste pile, and the pile will be repaired by contacting the design.

Cast-in-place piles are generally large-diameter piles, so the stability of cast-in-place piles themselves has a very important role, and in order to comprehensively improve the bearing capacity of cast-in-place piles, the distribution of reinforcement needs to be carried out according to the internal force state of pile body. When carrying out construction, in order to reduce the influence of surrounding buildings, need to control the construction noise, and the scope of control is also relatively wide. At the time of cast-in-place pile construction, it needs to be poured into a pile first, and then utilize various construction techniques to carry out comprehensive comprehensive construction, ensure that the quality of cast-in-place will not be affected.

But in the process of actual operation, there are many influencing factors for cast-in-place piles, so it is very easy to cause pile body defects, and the quality of the whole cast-in-place pile has been affected.

There are two main common defects of concrete cast-in-place piles:

1. Common defects of underwater cast-in-place piles.

For underwater cast-in-place pile, due to the different construction methods, the defects that are easy to appear mainly mainly have the problem of broken pile or the problem of mud inclusion or sand inclusion in the section; There is mud inclusion or necking in the local cross-section; dispersed mud masses and "honeycomb" defects; Defects such as concentrated porosity. Fundamentally speaking, the situation that sand is included or mud inclusion occurs more commonly, mainly because the infusion conduit is not reasonable to cause, when carrying out new concrete injection, it is easy to enclose mud and sand and the like in it, and causes the situation that fault sand is included or mud inclusion appears. The occurrence of dispersed mud mass is mainly due to concrete disturbance or spalling, the gas in it can not be discharged completely, and then honeycomb concrete defect appears, and this defect has a very serious impact on the quality of concrete cast-in-place pile, but if the area is small, can not be treated.

2. Common defects of dry-hole cast-in-place piles.

For dry-hole cast-in-place pile, its main defect has concrete layered segregation or broken pile; local mud inclusion or "honeycomb" defects; Severe local segregation and pile bottom sediment. Wherein concrete layered segregation or broken pile is caused by groundwater influx, after pouring concrete, is washed or soaked by groundwater, can cause the emergence of layered segregation. In addition, pile bottom sediment is due to the fact that when carrying out construction operation, the hole is not comprehensively cleaned up, and the pouring of concrete is carried out, and the situation that pile bottom sediment occurs.

In order to ensure that the quality requirements of cast-in-place piles can meet the standard, it is necessary to use non-destructive detection technology to carry out quality inspection of cast-in-place piles, and acoustic tube detection is one of the most widely used methods.

The conduit is 300-500mm away from the bottom of the hole, and the first irrigation ensures that the conduit is buried more than 1m, and the conduit is buried in concrete 2-6m during the pouring process, and the conduit cannot be pulled out of the concrete surface.