3.
If the deviation of pile position is too large due to the disturbance of mechanical operation, the borehole shall be filled with mortar and re drilled into a hole.
4.
On the contrary, it is felt that the tendon has a sense of adhesion by inserting soft soil, indicating that the sediment thickness is too large.
(3) After the reinforcement cage is lowered, the pile hole bottom inspection must be carried out again before pouring concrete.
4.
Before the hole forming construction of rotary drilling pile foundation, the engineering department must organize the drilling construction unit to conduct a detailed survey of Engineering Geology (one pile and one hole shall be drilled in advance).
The outer wall of the casing shall be welded with a ring-shaped support plate (wall thickness 10mm).
Concrete pouring (1) when the groundwater is abundant and the water level is high, the underwater concrete pouring construction process shall be adopted.
When the pile length is ≤ 15m, the low strain dynamic detection method can be used, and the acoustic transmission method can be used according to the proportion of 10%.
There shall be no less than 2 on-site supervisors for each building.
When the rock socketed depth enters the rock layer, use a rock drill bit to drill (preferably a coring drill bit), record the absolute elevation when entering the bearing layer, measure whether the hole bottom elevation reaches the design pile bottom elevation, and check whether the rock socketed depth meets the design requirements.
When the soil is soft and the groundwater level is high, in order to prevent hole collapse, hole jamming and other accidents, slurry wall protection shall be adopted, and slurry preparation shall be completed before drilling construction.
(4) When the reinforcement cage is placed, the reinforcement cage shall be fixed, and deviation is strictly prohibited.
Bit preparation: mud drill is used for clay layer, sand drill is used for loose gravel and sand layer, and rock bit must be used for rock socketed pile.
(2) To judge the sediment thickness, 3-4 steel bars ≥ 20 can be welded into bundles, and then hoisted into the hole bottom with ropes.
2.
7.
8.
The project manager of the construction unit must have rich construction management experience and successful cases of rotary excavation pile construction (more than three successful cases in the past by the on-site investigation project manager).
Strengthen on-site supervision (1) supervision of the whole process of advance drilling.
The distance between the bottom opening of the tumbling barrel and the hole bottom or concrete surface shall be controlled within 2m.
Hole cleaning quality (1) the hole cleaner of sand fishing bit must meet the hole cleaning requirements and be processed by itself if necessary to ensure that the hole cleaner is slightly smaller than the pile diameter by about 200.
The chief engineer office shall determine the design pile bottom elevation of each pile according to the advance drilling results.
The concrete pouring gap time shall not be greater than 20 minutes.
6.
When the hole soil layer is relatively soft, after the accurate positioning of the pile position, a steel casing (wall thickness 10mm) with a length of 2 ~ 3M shall be set at the top of the pile.
Inspect the integrity of concrete piles and determine the degree and location of pile defects.
When the groundwater is rich and the water level is high, the underwater concrete pouring construction process shall be adopted, and the tremie and auxiliary machines and tools for pouring concrete shall be prepared before lowering the reinforcement cage.
If necessary, they shall be processed by themselves to ensure that the hole cleaner is about 200mm smaller than the pile diameter.
After the pile position is accurately positioned, a steel pile casing with a length of 2 ~ 3M shall be set at the top of the pile to avoid the impact of the surrounding earth and rock during tripping, lifting and lowering the reinforcement cage, resulting in the slag falling into the hole, so as to ensure the integrity of the pile hole and no sediment at the bottom of the hole.
2.
（5） Detection points 1.
(4) Sufficient preparations must be made for concrete pouring to ensure continuous construction, and the concrete pouring interval time shall not be greater than 20 minutes.
Wellhead casing.
4.
It is qualified when the feel is that the tendon has a rebound feeling of collision with hard objects.
2.
(3) The reinforcement cage shall be lifted gently and placed slowly, and attention shall be paid to avoid collision with the earthwork of the hole wall.
(3) Supervision of the whole process of concrete pouring.
1、 Key points of construction quality control of rotary excavation pile （1） Personnel preparation 1.
Pile hole positioning (1) place the pile position before the drilling rig is in place.
Fabrication and placement of reinforcement cage (1) the type, specification, quantity and size of reinforcement must meet the design requirements.
When the pile length is more than 15m, the acoustic transmission method shall be used to detect the defects and positions of the pile body and determine the integrity category of the pile body..
If the sediment at the hole bottom is found to be too thick, the reinforcement cage must be pulled out and the hole cleaned again.
Concrete preparation.
Preparation of hole Cleaner: hole cleaners with different diameters must be prepared according to different pile diameters.
(3) The initial concrete pouring volume shall meet the minimum buried depth of 0.8 ~ 1.0m.
Under the guidance of the manager of the engineering department and the project manager, carefully prepare the detailed rules for the construction supervision of rotary excavation piles, clarify the contents and procedures of supervision application for inspection, main quality control indicators and quality acceptance standards, and submit them for approval as required.
Check and recheck the verticality of pile position and pile hole; Measure the rock penetration elevation and hole bottom elevation of the pile hole, and recheck the rock socketed depth; Check the hole cleaning quality.
（3） Material preparation 1.
Mud preparation.
When there is no water in the hole or the water seepage is very small, the tumbling barrel method shall be adopted for pouring.
When pouring concrete, the pulling out time shall be controlled and pulled out by sections.
If the hole collapse is particularly serious, the steel plate can be self-made and processed into a sleeve.
The tumbling barrel shall be aligned with the pile center as far as possible to make the concrete fall freely in the hole and increase the impact force and compactness of the concrete.
Check the placement of reinforcement cage and recheck the sediment at the hole bottom; Inspection of conduit lowering position; Concrete slump test and witness sampling of concrete strength test pieces; Continuity supervision of concrete pouring.
The thickness of the steel plate shall not be less than 10mm and pressed evenly from top to bottom.
2.
If earth falls, the hole needs to be cleaned again.
4 ~ 6 reinforcement locators shall be installed outside the main reinforcement on the same section, with a spacing of 3M along the pile length.
9.
When selecting the model of mechanical equipment, the maximum hole diameter, maximum hole depth and other parameters must meet the requirements of foundation pile design and construction, and the torque shall not be less than 200kn · M.
(5) During pouring, the tremie shall not be lifted out of the concrete surface.
Before placing the reinforcement cage, each pouring operation team on site must prepare the concrete of the whole pile, and keep 1 tank truck waiting for concrete during the concrete pouring process, so as to ensure the timeliness and continuity of concrete pouring.
Drilling verticality during drilling, the drill pipe verticality shall be checked without deflection, so as not to affect the hole forming quality.
Before placing the pouring concrete conduit, the tightness of the conduit joint and the water isolating bolt shall be checked to prevent mud from penetrating into the pipe, and the lower end of the conduit shall be controlled within 200mm from the hole bottom.
Before lowering the reinforcement cage, the tumbling barrel and auxiliary machines and tools for pouring concrete shall be prepared.
3.
The allowable deviation of perpendicularity is 0.3%.
（4） Key points of construction control 1.
The buried depth of the tremie shall be 3.0 ~ 4.0m and the small buried depth shall be 1.5 ~ 2.0m to avoid pile slag and pile breaking.
(2) In order to ensure the thickness of the concrete protective layer of the pile body, use φ 12.
Treatment of hole collapse for general hole collapse, cement mortar or low-grade concrete can be poured and re drilled.
3.
Before the drilling rig starts drilling, be sure to recheck the pile position coordinates to avoid disturbing the pile position when the drilling rig moves, and try to skip the drilling.
Preparation of tremie and tumbling barrel for concrete pouring.
Implementation of on-site supervision personnel.
(2) After drilling for 5 ~ 8m, the supervising engineer must recheck the intersection coordinates of the cross line at the upper opening of the casing to ensure the accuracy of the pile position.
（2） Mechanical preparation 1.
(2) Supervision of the whole process of rotary drilling.
(6) The pouring elevation of pile top shall be controlled according to the design elevation plus 500-1000mm, so as to chisel the mortar and pile head.
5.
10.
The commonly used imported equipment brand “CRRC” 2.
The wing of the support plate is 500mm wide and 200mm away from the upper opening of the casing, so as to avoid the impact of slag and soil on the surrounding earth and rock during tripping, lifting and steel reinforcement cage, which will affect the quality of hole forming and hole cleaning, It can also control the pile position during drilling.
Check and recheck whether the drilling hole meets the requirements of one pile and one hole; Measure the elevation of drilling hole orifice and hole bottom; Witness drilling and coring and record.
(2) When there is no water in the hole or the water seepage is very small, the tumbling barrel method can be used to pour concrete.
The depth of the advanced drilling hole shall meet the requirements of three times the pile diameter below the rock socketed depth of the bearing layer and no less than 5m (whichever is greater).
The project manager shall organize the preparation of targeted rotary excavation pile construction scheme and submit it for approval as required.
(4) Supervise the whole process of pile foundation testing to ensure the authenticity of testing results.
The slump of non underwater pouring concrete should be 8 ~ 250px, and the slump of underwater pouring concrete with conduit should be 18 ~ 550px.
The concrete shall be followed up in time to ensure that the hole does not collapse, and the steel sleeve can be reused.
