Construction preparation for rotary drilling

1. Data preparation

(1) Site engineering geological data and necessary hydrogeological data should be available before the start of construction, and the construction drawings and drawings of the pile foundation project will be reviewed.

(2) Survey data of underground pipelines (pipes, cables), underground structures, dangerous buildings, precision instrument workshops, etc. in the site and adjacent areas.

(3) The technical performance data of the main construction machinery and its ancillary equipment, the inspection of the required materials and the mix ratio test. The physical properties of the materials must be tested for the required materials, and the qualified laboratory is entrusted to use the raw materials used. Good concrete mix ratio test.

(4) Construction organization design or construction plan with effective pile foundation engineering, and test reference materials related to load and construction technology.

2. Construction machinery and equipment

The measuring instruments used, such as theodolites, level gauges, steel tape measures, rotary drilling machines, electric welders, etc., must have a factory certificate.

3. Requirements for small and medium-sized machines

(1) Mixer

The installation of the body is solid and stable, and it is equipped with a rainproof operation shed; all kinds of clutches, brakes, wire ropes and protective covers must be safe, reliable and effective; the operator should be certified to work; there must be a good separate grounding.

(2) Handheld power tools

The leakage protector must be installed separately; the protective cover is safe and effective; the outer casing must be grounded or connected to zero; the rubber wire is not allowed to be damaged.

(3) Electric welder

Have reliable rain protection measures; have good grounding or zero protection; first and second line wiring should have a complete protective cover; secondary line should use wire nose; wiring is not allowed to mess, pull, insulated Good; welders are certified to work.

(4) gas cylinder

All kinds of gas cylinders have obvious color code and anti-vibration ring, and are not allowed to be exposed to the open air; the distance between acetylene gas and oxygen cylinder should be greater than 5m; acetylene gas cylinder must be equipped with tempering preventer when used; Operators must be certified to work.

4, the installation of drilling tools

The drilling tool has a certain rigidity. During drilling or other operations, no movement or shaking occurs. The drilling tool should be installed in accordance with the manufacturer's standards. It can be used with short drills, rotary buckets, core drills, core rotary drills and other drills of various specifications. During construction, according to different soil and geological conditions, the drill bits of different rotary drilling machines are selected according to the following regulations: short spiral drilling tools, suitable for cohesive soil, silt, filling soil above groundwater level, sand above medium density. , weathered rock formations. The spiral slewing head is made of mud retaining wall and is suitable for cohesive soil, silt, sand, fill, gravel soil and weathered rock layer above the groundwater level. Core auger bit for gravel, medium hard rock and weathered rock. Core drill bit for weathered rock formations and cracked rocks. The drill specifications are selected by the user according to the actual engineering conditions.

5, commonly used clear water construction process

Rotary drilling and drilling process of drilling machine: Rotary drilling into holes is firstly to break the rock through the barrel drill with the shutter at the bottom, and directly into the drill bit, and then the lifting device of the drilling machine and The telescopic drill pipe unloads the drill bit from the outside of the hole, so that the cycle is repeated, and the earth is unloaded until it is drilled to the design depth. For the cohesive rock layer, the dry or clear water drilling process can be used without mud protection. For the loose and easy collapsed stratum, or the groundwater distribution, the pore wall is unstable, the static mud retaining wall drilling process must be adopted, and the retaining wall mud or the stabilizing liquid should be put into the hole to protect the wall. In the following, only the construction process of the rotary-boring and soil-forming method is discussed.

(1) The hole forming process of the clear water construction process:

In the process of forming holes, no mud retaining wall is needed, but the mud self-created by the drill bit during the slow rotary drilling process has a certain stabilizing effect on the hole wall. During the rotary drilling process, the drill bit runs between the bottom of the hole and the surface of the hole. The wall of the hole formed is relatively rough. The bite cooperation between the pile and soil of the rotary-drilled bored pile is stronger, which can better reflect the interaction between the concrete pile and the loess and silty clay.

(2) Site layout principles

According to the design requirements, the construction site should be arranged reasonably, firstly level the site, remove debris, replace soft soil, and beat the compact. After the site leveling, organize the qualified measurement stakeout personnel, release all the pile positions, nail the cross protection piles, make a measurement review, and record the stakeout data for the record; when planning the driving route, keep the access road and the drilling position A certain distance; so as not to affect the stability of the hole wall; when the construction site is dry land and the groundwater level is below the original ground during construction, the site is leveled and smashed to remove debris; when the site is in shallow water, the drilling machine is installed on the top surface after the island is built. The top surface of the island is about 1.0m above the construction water level; the chassis of the drilling machine should not be placed directly on the unfilled fill to avoid uneven subsidence; the placement of the drill should be considered for the excavation of the hole during the drilling. Convenient to transport.

(3) stake placement

When the pile position is staked, the position of the pile foundation is staked according to the principle of “from the whole to the local part”. When the elevation of the drilled hole is staked, the elevation of the staked sample should be checked in time. Use the total station to accurately stake out the position of each pile point so that the error is within the specification.

(4) Drilling machine in place

When the drilling machine is in place, check the performance of the drilling machine in advance. Ensure that the drilling machine is working properly.

(5) buried steel casing

(6) The method and requirements for burying the casing under the premise of accurate stakeout and burying the casing shall comply with the provisions of JTJ041-89 (hereinafter referred to as the “Specifications”). If the drilling is carried out on land, the pit method is generally used, which is relatively simple and easy.

(7) The steel casing is buried at the beginning of the construction of the rotary drilling machine. The plane position and verticality of the steel casing should be accurate. The circumference of the steel casing and the bottom of the casing should be tight and impervious.

(8) When burying the steel casing, the position of the drilling hole of the drilling machine shall be marked on the bottom of the pit through the positioning of the controlled control pile. Then hoist the steel casing into the pit, find the center position of the steel casing, use the cross wire at the top or bottom of the steel casing, and then move the steel casing to make the center of the steel casing coincide with the drilling center of the drilling machine. . At the same time, check with a horizontal ruler or a vertical ball to make the steel casing straight. After that, the clay with the best water content is backfilled symmetrically and uniformly around the steel casing, and the layer is compacted to achieve the best compactness. In order to ensure its verticality and prevent mud loss and displacement, and fall, if the bottom layer of the casing is not cohesive soil, it should be dug or earth-changed. After backfilling the clay with a thickness of 300-500mm at the bottom of the pit, install the casing to avoid Leakage of the bottom of the casing is prevented, and the steel casing is prevented from being skewed when filling. The upper edge of the casing should be tied and tied with a wooden symmetry to prevent squatting.

(9) Principles of making and burying steel casings

Steel casings with a length of 4m or less are made of steel plates with a thickness of 4-6mm. Steel casings with a length of more than 4m are made of steel plates with a thickness of 6~8mm. When steel casings are buried deep, they are connected by multi-section steel casings. The connection form is welded. When welding, the joint is rounded, and the requirements of rigidity, strength and leakage are met. The inner diameter of the steel casing should be larger than the diameter of the drill. The specific size is selected according to the design requirements. The depth of the steel casing should meet the design and Relevant specification requirements. If the pile hole is in the river, the steel casing should be buried to a depth of more than 0.5m in the harder and dense soil layer; the top of the steel casing is higher than the construction water level or the groundwater level 1.5-2.0m, and is 0.3m above the construction ground. Before the steel casing is buried, accurately measure the stakeout to ensure that the position deviation of the top surface of the steel casing is not more than 5cm, and the slope of the steel casing is not more than 1% in the embedding; before the steel casing is buried, the drill with a larger diameter is used first. After pre-drilling to the elevation position of the bottom of the casing, the drill collar is proposed and the steel casing is pressed into the predetermined position by the drill bucket. Backfill the outside of the casing with coarse-grained soil and backfill it.

Geological conditions records are recorded according to the corresponding geological related tables; when drilling and drilling the drilling machine, fill in the “Drilling Record Form” in time, the main contents are: work item, drilling depth, drilling speed, and bottom of the hole. Elevation; "Drilling Record Form" is filled in by a special person, and there should be a handover record when handing over the shift; according to the change of the drilling speed of the rotary drilling machine and the sampling of the soil layer, the geological conditions are carefully recorded, and the geological section of the hole pile is drawn. In the figure, each hole pile must be provided with a soil geological sample box, and the position and sampling time of each sample in the hole pile are indicated in the box; when the geological section of the rotary drilling machine hole pile is inconsistent with the design, it is submitted to the supervision site in time. Confirm that the design unit determines whether to change the design; when drilling, it is necessary to clear the hole slag in time to avoid obstructing the drilling construction and polluting the environment; after the drilling reaches the predetermined drilling depth, lift the drill pipe and measure the hole depth. The thickness of the virtual soil (the thickness of the virtual soil is equal to the difference between the depth of the drill and the depth of the hole).

(11) Hole inspection

After the hole has reached the design elevation, the hole depth, the hole diameter, the hole wall, the verticality, etc. are inspected, and measures are taken when the film is unqualified. The hole inspection method is determined according to the condition of the hole diameter. When the hole is a dry hole, the virtual soil in the hole can be compacted by a heavy hammer, and the wire can be directly measured by a measuring rope and a hole measuring device. The method of suction and reverse circulation pumping is used to clear the hole, and the underwater pouring concrete construction method is used to carry out the hole drilling work of the hole. When the hole is cleaned, the viscosity and the sand content of the mud are controlled reasonably; the pile hole qualified by the quality inspection is timely poured. Concrete.

(13) Clearing holes

Clearing the hole is an important part of the construction of the hole pile to ensure the quality of the pile. The quality index of the pile hole, the thickness of the sediment at the bottom of the hole, the amount of drilling slag contained in the circulating liquid and the mud wall of the hole wall are ensured by the clear hole to meet the quality requirements of the pile hole. The clearing method of the positive circulation rotary drilling technology is: after the final hole of the pile hole, the drilling tool is increased by 20 to 50 cm, and the new mud with the performance index meets the requirements is pumped with a large pump volume, and the positive circulation is maintained for more than 30 minutes until the hole is cleared. The bottom sediment and the mud wall of the pore wall and the mud content of the mud are less than 4%. Because of the thick loose and easy soil layer, the pile hole of the project can not immediately terminate the hole after clearing the hole, but the steel cage is placed in the hole, and the second hole cleaning operation is performed after the grouting pipe is installed, so that the bottom of the hole before the infusion The thickness of the sediment meets the requirements to ensure the quality of the column.

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