Rotary drilling rig construction method

【China Deep Hole Rig Trading Network】

I. Introduction

In recent years, the construction period of expressways has become shorter and shorter, and there is only a period of 18 months for super-large bridge projects. How to speed up the construction of bored piles in the lower part of the bridge under the premise of guaranteeing project quality is to ensure the completion of construction on schedule. The essential.

Second, the characteristics of engineering methods

1. The hole forming speed is fast and the efficiency is high. The average drilling speed is: 5m-8m/hour.

2, can dry hole operation, but also drilling in the water, less sediment in the hole.

3, less water is used for drilling.

4. No mud pollution on the construction site, the site is relatively clean and no noise.

5, can walk on their own, drill in place, shift quickly, their own power.

6, the device performance is good, the computer coordinates positioning and display drilling verticality, high quality of hole formation.

Third, the scope of use

Rotary drilling rig is suitable for clay soil, sand soil, gravel, pebble layer, soft stone layer, strong weathered rock formation, and other geological conditions with relatively small contents, and operates under flat geographical environment. This method is mainly applicable to the pile foundation construction under conditions of silty soil in a dry and rainless area or when underwater holes are formed. The maximum drilling depth is 60 meters.

Fourth, the principle of technology

The construction of static mud rotary drilling rigs is to apply pressure to drum bits or screw bits through the hydraulic system of the rotary drilling rig and its own weight. Under the load conditions, the drill bit is rotated and drilled through the rotation of the drill pipe. When the drill bit or spiral After the drill bit is full of drill slag, the drill pipe is shrunk, and the drill bit or spiral drill bit is raised out of the hole, and the bottom cover of the drill bit is opened or the drill bit is driven to rotate to remove the drill slag in the drill bit. At the same time, the slurry is injected into the hole with a mud pump, and a film is rapidly formed on the hole wall to reduce the water loss rate and maintain the height of the water head in the space.

Fifth, process flow and operating points

(I) Process flow (flow chart of static mud rotary drilling rig construction process)

(b) Operational points

1. Site formation: The position of the rotary drilling rig is compacted and the site is leveled. The rotary drilling rig, crane, and concrete tanker are suitable for the construction machinery to enter and leave the construction site. Construction site water, electricity, road three links, to meet the construction requirements.

2. Measurement and positioning: Before the start of construction, coordinate all the pile base coordinates provided by the drawing, and the measuring instrument should be used after passing the inspection. Measure the elevation of the ground and set the elevation of the construction platform according to the construction requirements. Accurately measure the center position of the pile. After the casing is buried, the pile position should be checked and cross-protected piles should be installed.

3. The rig is in position: The tracked rotary drilling rig has an automatic walking system. The rotary drilling rig walks in and aligns. After the centering is completed, the relative coordinates of the pile center are set and locked, and the center coordinate of the pile foundation is set as (0,0,0) and enter it into the rotary drilling rig computer system. Using a total station or theodolite to review the verticality of the drill pipe.

4, buried casing: casing should use 10-12mm steel production, diameter larger than the pile diameter 30-40cm, casing height 200-250cm, with a rotary drilling rig press the casing into the soil, so that the casing center and pile The design center is consistent, the center deviation is less than 5cm, and the deviation of inclination is no more than 1%. The top surface of the protection tube should be higher than the groundwater level of 1.5-2.0m above the ground by 0.3m.

5. Review of the position of the pile foundation: After the casing is buried, check the position of the pile foundation before drilling.

6. Mud pool, sedimentation pond excavation and mud preparation

(1) Excavation of mud pools and sedimentation tanks: The location of the selected mud pools and sedimentation tanks prior to construction should be lower than the sedimentation tanks. The slurry flows into the mud pool after sedimentation so that the mud can be recycled. The size of the mud pool and the sedimentation tank are determined according to the diameter of the pile foundation and the hole depth. The volume of the mud pool is preferably 1.5 times the volume of the well bore. The sedimentation tank should be located at the position where the sediment can be easily cleaned, and its volume should be larger than the borehole volume. In locations where water is inconvenient, clear water tanks should be excavated.

(2) Mud modulation: For the easy collapse of silty soil layer, it is required that the speed of slurry protection wall is high and the effect is good. Therefore, a high-quality slurry obtained by stirring with bentonite, soda (Na2CO3) cellulose (CMC) and water was selected in a ratio of 25% of bentonite, 0.4% of bentonite as the amount of soda, and 0.1% of bentonite as the amount of cellulose. The ratio and performance are shown in the following table:

Mud mix table

Material Name Bentonite Cellulose (CMC) Soda Ash

Mixture ratio (%) 25 0.1 0.4

Mud performance

Project relative density Viscosity (s) Static force (pa) Sand content (%) pH HP colloidal rate (%) Water loss rate (ML/30min) Mud thickness (mm) Stability

The value 1.08-1.1 18- 22 2-5 <2% 8- 10> 98 14- 22 <2 <0.03

(3) The role of various materials and additives in mud

Bentonite: The main role of bentonite is pulping, and it has a higher pulping rate relative to clay. Make sure the slurry has excellent working performance.

Cellulose (CMC): The main role is to quickly form a layer of film on the pore wall, reduce the rate of water loss, and reduce the penetration of water to achieve the effect of water retention.

Industrial soda ash: The main role of industrial soda ash is to increase the pH of the slurry, disperse the particles in the slurry, increase the negative charge on the surface of the particles, increase their adsorption capacity and the thickness of the hydration film, thereby increasing the colloidal rate and stability of the slurry.

During the pulping process, the relative density, viscosity, pH, colloidal rate and other performance indicators in the mud pool are tested. The indicators of the slurry are put into use after meeting the requirements in the above table, and the slurry in the mud pool is suitable for testing before recycling. Its sand content, relative density, viscosity, pH, colloidal rate and other performance indicators, mud slurry in the mud pool rate should not exceed 0.5%. Otherwise, the mud should be sedimented and the sediment cleared to dry and the mud in the mud pool should be redistributed. The rapid accumulation and stratification during the perfusion process accelerate the precipitation. The precipitated mud is pumped into the mud pool by a mud pump, and is then recycled after being used.

7, drilling

(1) When using the total station or theodolite to review the verticality of the drill pipe and start the rotary drilling, at the edge of the protective tube, slow drilling should be performed at the low speed, so that there is a strong wall guard at the blade foot. After drilling to 1m below the cutting edge, the soil can be drilled at normal speed according to the soil quality. When passing through the silt layer, the drilling speed is slowed down. The speed of the footage must not exceed 3m/hour, increasing the number of drilling rigs for empty drilling to enhance the wall protection effect. The mud excavated by the rotary drilling rig is cleared off the construction site by a loader.

(2) Every drilled 2m or stratum change should be sampled from the drilling cylinder to identify the soil quality and recorded, and checked with the design data.

(3) Piles should be retested in the process of rotary drilling. When the hole depth is 20 meters, 40 meters and the final hole, use the hole detector (the hole detector is made of steel, the outside diameter is The bored pile reinforcement cage diameter plus 100mm, the length is equal to 4 - 6 times the aperture) inspection verticality, aperture, in order to adjust the diameter of the drill in time.

(4) During the drilling process, it is advisable to check the main indicators of the mud, mainly to measure the specific gravity and sand content of the mud.

(5) Rotary digging While drilling, use a mud pump to inject mud into the hole from the mud pool to maintain the head height in the hole.

8. Hole formation inspection: After the pile foundation has been formed into a hole, check the center and hole diameter of the hole with a hole checker, remove the sediment at the bottom of the hole with a cylinder drill, and check the hole depth with a measuring rope. At the same time, use a steel rule to check the rope. length.

9, clear hole: after the completion of the inspection hole with a cylinder drill for slag hole clearance, the clearance process speed should not be too fast, while maintaining the head height of the hole.

10, steel cage production, welding installation

(1) Reinforcing cage production: First, check the lengths and quantities of various specifications of steel bars in the construction drawings, and then adjust the steel bar bars, and the surface of the steel bars should be kept clean and straight. After the steel comes into play, it is cushioned with padding or other methods. When the steel bar is temporarily stored on the construction site, open spaces with high ground and dry ground should be selected. Rain and snow weather, if necessary, can be covered with canopy cloth according to weather conditions. In steel processing, according to the construction design drawings combined with the size of the steel bar raw materials for batching, processing, production, installation, can not arbitrarily change the length and structure of steel bars, all steel processing, welding meet the following requirements: the main reinforcement spacing within ± 10mm, stirrup spacing In the case of -20mm or less, the outer diameter of the skeleton is within ±10mm, the skeleton protective layer is within ±20mm, and the cross-sectional area of ​​the welded joint of the reinforcing steel is not more than 50%. Before the welding of steel bars, test welding was carried out according to the specific construction conditions (especially for butt welding construction), and then large-scale construction was carried out.

(2) Reinforcing cage welding installation: Before the installation of reinforcement cages, check the number of rebars, diameter, spacing, and whether the reinforcement cage is deformed. The welding points, welding length, width, and thickness shall meet the requirements of the specifications. In order to avoid deformation of the local reinforcement during lifting of the cage. When the steel cage is placed in the crane, each section of the reinforcement cage is guaranteed to have three lifting points, and the crane hooks are used to lift the reinforcement cage. In the welding of holes, lap welding is used to ensure that the upper and lower sections are in a straight line, evenly into the hole, and the position of the reinforcement cage is adjusted at any time, so as to avoid colliding with the wall of the hanging hole and the phenomenon of hole collapse.

(3) Test tube installation: The test tube is installed on the inside of the reinforcement cage and is distributed in equilateral triangles. The lower end of the steel pipe is flush with the bottom of the pile, and the upper end of the steel pipe is to expose the working plane of the drilling rig. The detection tube is installed straight and firmly, and the joints are not connected. The tube is welded and sealed. The slurry does not leak. The length of the tube is not less than 20cm. Both ends of the tube are welded and sealed with 3mm steel plates.

(4) After installation of the steel cage, measure the sediment thickness at the bottom of the hole. When the sediment thickness exceeds the requirements of the construction specification, apply a small-diameter cylinder drill to remove the sediment. Calculate the sedimentation velocity at this stage after sedimentation.

11, down the catheter

(1) The conduit is installed under the condition that the sedimentation velocity is ≤ 5cm/h and the sediment thickness meets the specification.

(2) According to the hole depth to prepare a sufficient length, different length of the catheter, the diameter of the catheter between 28-35CM.

(3) Before the catheter is used, it should be tested and tested for airtightness. Sufficient top wire and apron should be provided. The catheter should be straight and sealed to prevent water leakage.

(4) When installing the catheter, special inspection should be performed. Each section of catheter should be tightened with special tools. The distance from the bottom of the conduit to the bottom of the hole must not exceed 40 cm.

12. Secondary hole cleaning: after the installation of the pipeline is completed, it is advisable to carry out the second hole cleaning. The slurry pump with the head of not less than 20m is used for the positive circulation clearance hole to reduce the mud weight and sand content, and the secondary hole clearance time is 1 to 2 hours is appropriate. After the proportion of mud and sand content meet the construction requirements (ratio of mud between 1.08 and 1.10, viscosity of 18-22S, sand content ≤ 2%), underwater piling of the pile foundation will be performed immediately.

13, pouring concrete

(1) Mixing and supplying: Check the quality and quantity of cement and sandstone before pouring concrete. Concrete mixing should be carried out according to the laboratory to provide mixing ratio. Mixing equipment should be checked before concrete mixing to check the accuracy of the measurement system. In particular, check the water consumption regularly. System, otherwise it will affect the concrete strength. Precisely measure the moisture content of the aggregate before mixing the concrete to adjust the mixing water consumption. The slump of concrete should be controlled between 180-200mm, and concrete slump should be measured every 10m3-20m3. The amount of poured concrete was recorded by field technicians, and the depth of the buried pipe and the surface height of the concrete were measured and recorded at any time.

(2) The first batch of hydrazine infusion quantity: When the ball is cut, the concrete tanker shall continuously transport the hydrazine into the storage hopper. The amount of the first irrigation concrete should not be less than the depth of the first buried concrete should be ≥1.5m.

(3) Continuous perfusion

A. When pouring, a cake made of steel plate with an outer diameter slightly larger than the inner diameter of the catheter is suspended by a steel wire rope as a hinge-type “shear ball” device. During the concrete pouring process, the hoisting capacity of the wire ropes and cranes for lifting storage hoppers and pipes shall not be less than 16t, and the cranes shall be placed on the holes.

B. When the helium is transported to the infusion site, the on-site technician tests the uniformity and slump of the concrete of each vehicle, and the infusion is performed after the requirements are met. After the beginning of perfusion, it should be performed continuously and the time for removing the catheter should be shortened as much as possible. When the inside of the duct is not full, the concrete shall be slowly poured to prevent the formation of high-pressure air bags inside the duct.

C. When disassembling the catheter during the perfusion process, use the depth of the sounding hole to measure the position of the concrete surface in the borehole, and timely adjust the depth of the catheter so that the depth of the catheter is within 2-6 m.

D. When pouring into the top of the pile, use a crane to lift the pipe (the depth of the pipe is greater than 2m in the concrete when lifting).

E, perfusion pile top elevation of 0.5m-0.1m. The pre-adding height shall be removed after excavating the foundation pit after excavation, and the pile body shall be prevented from being damaged when excavated. Within 24 hours after the completion of underwater concrete infusion, bored pile construction or other vibratory operations shall be carried out within 5m of the pile position to protect the newly cast concrete. Twenty-four hours after the completion of the underwater concrete infusion, the top of the pile was buried by using a soil burying method.

14. Pull out the casing: After the concrete is poured, remove the casing with a crane or rotary drilling rig.

15. No damage detection of pile foundation: 15 days after the completion of concrete pouring, the testing unit with corresponding qualification shall be allowed to carry out the damage detection of the pile foundation. Then proceed with the construction of the next process cap and tie beam.

Seventh, machine equipment

Major machinery and equipment

Machinery Name Mechanical Model Quantity

Rotary drilling rig AF180 1

Loader ZL50 1 set

Crane 20T 1

Mud pump 30KW 3 sets

Conduit D=28-35CM meets construction requirements with no less than 1m3 hopper

Concrete Mixer 750 2 sets

2 units

VIII. Labor Organization and Security

(1) Labor Organization

1. One person in charge of the scene and one technician.

2. Two rig operators, 6 mud sculptors and 2 loader drivers.

3, 25 steel workers, 5 welders, 6 directors of concrete irrigation, and 1 heavy worker.

(II) Construction Safety

Drills and drill rods should rise and fall steadily in the holes to prevent them from colliding with the protection tube and the retaining wall. When entering or exiting the holes, it is forbidden to stand near the mouth and prevent the drill cone from colliding with personal accidents. When the drill is stopped for any reason, the hole should be covered and protected, and the drill cone must not be left in the hole to prevent it from being buried. Do not drill holes to prevent sticking. After receiving training, special operators are qualified to take up posts. The safety personnel must go deep into the construction site and supervise the operators and commanders to abide by the operating procedures and stop illegal operation, unlicensed operation, illegal command and illegal construction.

Nine, quality requirements

Bored pile quality requirements

No. Item Permissible Deviation Remarks

1 hole position center group pile ≤100mm; single row pile ≤50mm

2 Aperture not less than the design pile diameter

3 deep hole friction piles not less than the designed pile length; supporting piles exceeding design depth of not less than 50mm 4 inclination ≤ 1%

5 sediment thickness is not greater than the design requirements

6 Mud index after clearing hole Relative density: 1.08-1.1; Viscosity: 18- 22s; Colloidal rate not less than 98%; Sand rate ≤ 2%

X. Benefit Analysis

The use of static mud rotary drilling rig construction will accelerate the construction progress to the maximum limit. It takes only 30 minutes from the drilling rig to place, the casing to be buried, to the start of drilling, and for the generalized soil layer, the average drilling speed is 5-8m/hour. , It is 10-15 times the speed of general impact drilling ruler. Because the rotary drilling rig is powered by itself, it saves a lot of line costs and electricity costs, and at the same time it also saves a lot of mud removal costs. The construction site is free of mud pollution, no noise, and the site is tidy. The construction progress is fast, the quality of hole formation is excellent, and it has good economic and social benefits.

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