(1) Opening mode of reaming bit
1) reaming method of reverse circulation rotary drilling rig (Figure 2-23):
Figure 2-23 Opening Mode of Reverse Circulation Reaming Bit
Open: at the specified bottom expansion depth, open the bottom expansion wing plate from top to bottom to expand the bottom. The upper open bit is simple in form and convenient to process, and is mainly used to stabilize the soil layer.
Open down: at the specified depth of bottom expansion, open the bottom expansion wing plate from bottom to top to expand the bottom. The lower open bit has the advantages of simple structure, convenient machining, small reaming angle and good hole-forming reliability, and is suitable for complex strata, but the cutting torque is large.
Sliding type: the wing plate of the enlarged bottom slides down along the inclined fixed guide frame and is slowly cut to form the enlarged bottom. Sliding bit has complex structure, difficult machining and small adjustment range of enlarged bottom diameter, but it does not cut the hole wall repeatedly, so the hole is reliable.
Push-out type: the under-reamed bit rotates around the eccentric shaft and pushes out along the diameter direction to form the under-reamed bit. The structure of push-out bit is very complicated, and it is mainly used for submersible drilling.
Figure 2-24 Bottom Enlarging Mode of Drill Bucket
2) Bottom expanding mode of drill bucket (the drill bit does not move down as a whole, but expands and expands in situ, as shown in Figure 2-24):
In-situ push-out type: the method of pushing out the inclined wing plate of 12 and then expanding the bottom.
In-situ sliding type: the method of expanding the bottom by sliding the expanding blade along the fixed guide rod with an inclination angle of12.
In-situ downward opening and horizontal push-out: the bottom-expanding method of slowly opening the closed bottom-expanding wing plate at the upper part and horizontally pushing out the bottom-expanding blades at the lower part.
(2) The basic structure of the under-reamed bit.
1)YKD series hydraulic under-reamed drill bit (Figure 2-25): This series of drilling tools includes drill bit, pump station, console and rotary joint, and belongs to the three-wing downward-opening type. Through the ground hydraulic control and detection device, the opening and closing amount of the drill bit wing can be accurately controlled, and the enlarged bottom hole diameter can be determined at any time, which is convenient and accurate. Suitable for reaming at any depth. The drill bit is equipped with aileron, which can adjust and enlarge the diameter of the bottom section. The tool can be replaced after wear. Suitable for all kinds of sand and clay layers, cemented gravel layers with particle size less than 100mm, weathered bedrock below Grade IV, reverse circulation rotary drilling, drilling (foundation hole) and bottom expansion (bottom).
Figure 2-25 YKD series hydraulic reaming bit
Figure 2-26 KDJ- 1500 reamer bit
Figure 2-27 Drill Bucket Reaming Bit
2)KDJ- 1500 type under-reamed bit (Figure 2-26): the bit is open with three wings. With the help of axial force, the guide shaft moves up and down axially, realizing the convergence and elongation of the bellmouth wing, and transmitting torque through the shaft sleeve and the inner and outer sections of the shaft. Diameter and length of drill bit (m): φ 0.9× 2.2 (convergence), φ 1.5× 1.3 (opening), maximum stroke 440mm, enlarged bottom hole center angle 160, length of transition section not more than 0.65m .. Suitable for sandy clay.
3) Reaming bit for drilling bucket (Figure 2-27): This reaming bit is used in conjunction with short spiral large-diameter drilling rig, and consists of reaming arbor, bulldozer, support frame, drilling cylinder slider, split bucket door and bucket door switch spring pressure bar mechanism. The outer diameter of the drill bit is 900mm, the maximum reaming diameter is 2600mm, the amount of soil taken each time is 0.25~0.30m3, and the maximum drilling depth is 28 m. The reaming drill bit is characterized by simple and reliable structure and high efficiency, which can complete reaming, soil taking and soil abandonment. The flat hole bottom can be cut into arc bottom, and the bearing capacity can be further improved; The sliding block has a large stroke, which increases the soil storage space of the drilling cylinder, and the cutter bar can be reliably retracted to the original position, thus avoiding the phenomena of drilling sticking and destroying the hole wall; The ejector rod is used to compress the spring to open and close the bucket door mechanism, and the soil can be unloaded by itself without manual assistance; Different cutter teeth or blades can be selected according to soil conditions, with good adaptability; The bottom of the bucket door is equipped with a pair of blades to clean up the virtual soil at the bottom of the hole, and an alarm for reaming in place can effectively grasp the reaming size.
summary
1. Drilling technology is to select the corresponding drilling equipment, drilling method and technology according to the requirements of geotechnical engineering, and drill holes with different diameters, depths and angles into the ground. As an important technical means in geotechnical engineering construction, drilling technology has been widely used.
2. According to the law of drilling (engineering hole), the construction methods of engineering hole can be classified in different ways, such as whether there is circulating medium in the hole, the crushing mode of rock and soil at the bottom of the hole, the position of subordinate power, tools for directly crushing rock and soil, etc. According to the special requirements of modern foundation construction for drilling, the characteristics of engineering drilling are different from other drilling techniques. For a single borehole, the main characteristics are: large diameter, shallow depth, and the drilled strata are mostly soft soil. For a construction project, the main features are: large number of engineering holes and small hole spacing. The main characteristics of engineering hole-forming construction methods are: many methods and diverse functions of drilling machines. As far as construction conditions are concerned, the main features are: construction is restricted by many conditions, such as environmental protection, underground working space, etc.
3. Non-circulating rotary drilling means that the broken cuttings are not removed by circulating hydraulic power of flushing medium, but by lifting the drilling rig and drilling tool mechanical system. The two most representative methods are spiral drilling and bucket drilling. Augers are divided into long auger and short auger. Because of the different ways of removing debris, the characteristics, applicable conditions and technological parameters of these two methods are also different. In terms of process parameters, it should be noted that the rotation speed has a dual role in long spiral drilling, which not only affects the drilling efficiency of the bit, but also affects the efficiency of conveying cuttings. Drill bucket drilling is suitable for dry drilling in cohesive soil. The drill bucket integrates the functions of crushing rock and soil and storing drill cuttings. Commonly used drill bits are cone bottom type, impact type, locking type, bottom open type, semi-closed type and enlarged bottom type. Rotary drilling rig is generally used for drilling large diameter, short screw and bucket. The drilling rig adopts multi-purpose modular design. Because drilling and slag discharge are carried out alternately, the telescopic drill pipe with special structure which can quickly lift the bucket is adopted.
4. The positive circulation rotary drilling technology is mature and has no formation limitation. Because the upward velocity of positive circulation is low, it is most suitable for the aperture within 800 mm In the drilling process, the appropriate bit should be selected according to the formation hardness; In the process parameters, the appropriate WOB, rotational speed and flushing fluid volume should be determined according to the formation conditions and bit types.
5. Under the condition of large diameter, reverse circulation rotary drilling has high rising speed, good slag discharge effect and high drilling efficiency. This method has no limitation on the diameter of drilling holes. At present, the commonly used types of reverse circulation rotary drilling are pumping reverse circulation, compressed air reverse circulation and jet reverse circulation. Pump-suction jet reverse circulation drilling technology has high efficiency within 50m interval; Gas lift reverse circulation drilling technology can not be used in shallow holes or has low efficiency. With the increase of hole depth, the drilling efficiency increases gradually. When the hole depth exceeds 200 m m, the drilling efficiency remains stable, and the selection of bit type and technical parameters (WOB, rotational speed) is similar to that of normal circulation, but the characteristics of reverse circulation rotary drilling should be paid attention to.
6. Wire rope percussion drilling is the oldest drilling method, especially suitable for gravel layer, boulder layer, hard soil layer and rock layer containing boulder, so it is still widely used at home and abroad. Punching grab drill can be used for humus soil, silt, solid clay, sand, quicksand and soft rock with great difference.
7. The pile hole construction method with enlarged bottom is a special pile hole construction method, and its purpose is to improve the bearing capacity of piles. Enlarging the bottom of pile hole mainly depends on expanding the bottom of pile hole with expanding drill. The expanding methods of rotary expanding drill mainly include upper opening method, lower opening method, sliding method and pushing method. There are some methods to enlarge the bottom of the drill bucket, such as in-situ ejection, in-situ sliding, in-situ opening and horizontal ejection.
Review thinking questions
1. Working process and applicable conditions of spiral drilling.
2. Working process and applicable conditions of drill bucket drilling.
3. Working process, applicable conditions and bit selection principle of positive circulation rotary drilling.
4. Working process, realization method and applicable conditions of reverse circulation rotary drilling.
5. Working process and applicable conditions of impact drilling.
6. Working process and applicable conditions of percussion drilling.