1 Circumferentially cut barrel drill and cone drill tooth Fig.
The safety risk of manual hole digging is high, and the footage speed of other hole forming methods is slow, which increases the construction period and cost.
3.2 Key points of operation 3.2.1 Pile casing embedment Set the pile casing according to the pile location, embed it vertically into the soil, make the center of the pile casing coincide with the center of the pile location, and mark and measure the direction line position of the control point on the pile casing with red paint.
The double bottom can be rotated at an angle to realize the opening and closing of the soil hole of the pick bit.
The operator should stop pressurizing, and the drill bit should alternately perform positive and reverse operations at the hole bottom.
Adjust the mast angle, operate the winch, align the drill center with the drilling center, adjust the drilling rig perpendicularity parameters, and make the drill pipe vertical.
3、 Construction process flow and key points of operation 3.1 Ring-cut coring and hole forming process flow Embedding casing → Construction preparation → Conventional drilling → Start drilling → Ring-cut coring drilling → Cut and take out core column → Circulation drilling → Hole forming.
The top surface of the slurry in the casing shall always be 1.0m-1.5m higher than the water level outside the hole or the groundwater level.
The maximum inclination of the drilling rig to the plane shall not exceed 4 ° when the drilling rig is in place.
The inner diameter of the pile casing shall be 200mm~300mm larger than the diameter of the drill bit.
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During the rotary excavation, the verticality should be monitored through the control panel, and any deviation should be corrected in time.
The circulating tank and the sedimentation tank are separated, and the mud is recycled.
Before and during drilling, the mud performance indicators shall be tested continuously.
According to the depth of rock entry displayed on the depth display in the operating room, it is judged that the depth of the drill bit entering the bedrock is 0.8m~1.0m.
Otherwise, the above method shall be used for drilling.
At the same time, a new type of high-strength drilling tool has emerged, and a rotary drilling rig capable of circumferentially cutting and coring has been developed.
If necessary, add proper amount of bentonite and sodium carbonate into the mud.
3.2.6 Circulation drilling The circulation drilling shall be conducted until the design hole bottom.
When drilling bored piles, when encountering hard rock strata, the conventional methods include manual hole digging, percussion drilling, or using rotary drilling rig or rotary drilling rig to construct pilot hole with small diameter drill bit, and then using large drill bit for secondary cutting.
Fig.
Select the clay that meets the requirements to make the mud.
The depth of the bit entering the bedrock surface should be controlled at 0.8m~1.0m each time.
3.2.5 Cut and take out the core.
During the drilling process of rotary drilling rig, the operator shall observe whether the drill pipe is vertical at any time and control the drilling depth through the depth counter.
The preface is based on the classification standard of rock hardness specified in the Code for Geotechnical Engineering Investigation.
The specific gravity of the mud is 1.15-1.25, the sand content is ≤ 4%, the viscosity is ≤ 28S, and the colloid ratio is ≥ 95%.
With the development of China’s machinery manufacturing level, the performance of rotary drilling rig is also continuously improved, and the power and output torque are continuously improved.
The rotary drilling rig has good performance and high efficiency, and has become the main market force in the field of foundation construction in recent years.
The drilling rig shall be in place stably without inclination and displacement.
At the end of each footage, reverse the drill bit by an angle to close the soil inlet.
3.2.3 Before conventional drilling enters hard rock stratum and when hard rock core cannot be drilled completely, conventional pick bit grinding drilling is adopted.
When the cone drill is drilling in the rock, the bit shall be lifted out of the rock drilling surface every 15min or so, and the mud in the hole shall be used to cool the bit, so as to prevent the drill from burning due to the high drilling temperature in the bedrock for a long time.
The drill bit is in a completely closed state to ensure that the soil in the barrel does not fall out of the barrel.
2 Circumferentially cut barrel drill Fig.
The rock core should be broken by using the cone, and then the rock core should be taken out to complete a circular cutting core drilling, as shown in Figure 3.
In order to ensure that the rock fragments rotated into the drill bucket do not fall into the hole during the lifting of the drill pipe, the bottom of the pick bit is a double-layer bottom.
② According to the actual situation of the site, select a suitable location to excavate the sedimentation tank.
Too large or too small entry depth is not conducive to the removal of the core.
The saturated uniaxial compressive strength is>60MPa, which is a hard rock stratum.
The rotation speed of the drilling rig should ensure the maximum power of the engine and the maximum rotation speed.
The deviation between the pile casing center and the pile position center shall not be greater than 50mm, and the deviation of the inclination shall not be greater than 1%.
At the beginning, the rotary excavation speed should be slowed down, the bucket should be placed stably, and the bucket should be lifted slowly.
Use the barrel bit for the annular cutting core drilling.
When drilling, the soil inlet is open and suitable for soil entry.
3.2.7 The hole shall be formed after the hole depth is detected by the measuring rope and the hole diameter is qualified by the hole detector.
The rock layer is circumferentially cut with a core in the middle, circumferentially cut barrel drill and the cone drill tooth, and circumferentially cut drilling are shown in Figure 1 and Figure 2.
The pile casing and the pit wall shall be filled with clay.
When each bucket is dug, the drilling slag is removed or the drilling is stopped, the grouting shall be carried out in time to keep the water head in the hole at a certain height.
3.2.2 Construction preparation ① The drilling rig shall be in place to drive the drilling rig to the construction pile position, so that its body perpendicularity, drill pipe perpendicularity and reinforcement bar at the pile position can be combined in three lines.
3.2.4 When the drilling is difficult, the rock mass has weathered fissures and is cut into rock blocks during drilling, which can be used to judge the hard rock stratum.
4、 Safety measures shall be taken to close the pile foundation construction area, use warning flags to close it, set up hazard warning signs, and assign special personnel to be on duty.
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Fig.
2、 The process principle is to use high-power rotary drilling rig, select machine-lock drill pipe and cone barrel drill, use the cone barrel coring bit to cut the annular groove in the drilling rock layer, and then stop pressurizing, alternately carry out positive and reverse operations at the hole bottom through the bit, and use the cone to break the rock core and take it out, so as to achieve rapid hole formation by circulating drilling.
The mud is mainly used to suspend the sediment and cool and lubricate the drill bit.
3 If the core taken out by circumcision drilling cannot be taken out completely, it is necessary to use a pick bit to break the core and dig it into the drill bucket and take it out of the hole.
1.
The tungsten steel head on the spherical tooth on the circumference of the cone barrel drill is used to roll at the bottom of the hole, and it is also accompanied by the sliding rolling and cutting of the rock mass at the bottom of the hole by the cone.
