At present, the rotary excavator has become one of the mainstream construction machinery for bored piles due to the advantages of advanced technology, success, speed and stability. Because the engineering geological conditions vary greatly from place to place, different engineering designs are unlikely to be completely consistent with the actual formation, and sometimes there will be great differences. Therefore, when the geotechnical construction unit undertakes the bored pile foundation engineering, the pile foundation drilling is faced with no small uncertainty. In the process of pile foundation drilling, if some technical problems are not handled properly, it will not only increase economic losses, but also pose a threat to the safety of engineering equipment and personnel. BelowLow headroom rotary excavation rentalManufacturers share the matters needing attention in rotary excavation construction in different strata.

Through the practical experience of using rotary drill bits for drilling in various formations in recent years, low headroom rotary drilling rental manufacturers have summarized the technical problems and solutions that often occur in the construction of rotary drill bits in more special formations.

1. low headroom rotary excavation rental manufacturers talk about soft soil and other collapsed strata

1. Characteristics of collapse strata such as soft soil and the risk of pore formation

If the underground water level is high in the soft soil layer (such as soft soil, newly accumulated backfill, newly accumulated loose sand), after the rotary excavation rig excavates the soil, even if the drill bit is on the mud protection wall, the cave wall is difficult to maintain Stable, easy to shrink the collapsed hole or neck. This stratum is distributed on the shallow surface. As the amount of collapse becomes larger, the ground around the borehole collapses and the protective tube sinks in many cases. If it is serious, it will also pose a threat to drilling equipment and staff. If this happens, especially if the hole protection belt is found to be hanging or sinking during the construction process, you cannot continue to drill by chance. Fill the hole as soon as possible, re-fix the hole protection belt, and then drill.

2. Construction method of rotary drilling

In soft soil, backfill and other places, with mud wrapped walls can not become an effective resin layer. An effective and safe method of rotary drilling is to take long protective cylinder wall measures. Each rotary drill bit is composed of three or so steel protective belts, a vibration hammer and a crane with sufficient pulling force according to the difficulty of drilling. The length of the steel guard plate can be lowered to the soft floor, and the diameter of the steel guard plate is 100mm larger than the diameter of the pile (too large, causing concrete waste). A bit that is too small can easily clip the protective cylinder. it is difficult to guarantee smooth construction). When using long protective belt retaining wall to rotate and dig holes, the following matters should be paid attention:

(1) Basically, it is necessary to confirm that there are no large-diameter stones of more than 100mm within the depth range under the protective belt. According to the diameter of Zhang Haotong each weight length, select the appropriate power of the vibration hammer.

(2) During small-diameter construction, the outer diameter of the drill pipe and the diameter of the pipe should be comprehensively considered. The outer diameter of the drill pipe should be less than the diameter of the pipe by more than 200mm. When the pipe length is large, the difference should be greater for the convenience of construction.

(3) To ensure the verticality under the steel shield, especially the drill pile with small diameter.

(4) After injecting concrete, pull out the protective belt in time.

(5) Close cooperation between the sinking steel protection cylinder and the rotary digging pile. After the steel shield is pulled out, the low headroom rotary excavation rental factory believes that it can immediately sink into the next construction hole. Such a flow operation can greatly improve the construction efficiency.

2. low headroom rotary excavation rental manufacturers talk about sand and silt layer

1. Characteristics and hazards of sand and silt layer

When drilling fine sand or solid soil, if the water table is very high when it becomes a hole, mud should be used to protect the wall into a hole. This formation has no adhesion between the particles, so it is easily washed away under the action of water flow. Since the rotary drilling rig directly takes soil to drill holes during drilling, the drilled soil is repeatedly raised to the ground by the drilling circuit. The drill string moves in the mud, and the external water flow of the drill string is faster, which is easy to cause the refining of the hole wall. The sand particles scoured from the cave wall further reduce the protective wall effect of the protective wall mud. It is more likely to cause problems such as neck protection and hole collapse.

2, low headroom rotary drilling rental manufacturers share rotary drilling construction methods.

The following measures shall be considered when the mud wall is used in the construction of silt layer or silt layer.

(1) Low headroom rotary drilling rental manufacturers share the appropriate reduction of bit separation and initiation speed, reduce the mud flow rate between the bit and the hole wall, reduce refining.

(2) Appropriately increase the extrapolation angle of the drilling teeth. Increase the gap between the hole wall and the side wall of the drill hole.

(3) Low headroom rotary drilling rental manufacturers share the appropriate increase in the area of the oil and water holes inside the borehole, reduce the negative pressure at the top and bottom during the drilling process, and reduce the flow rate of mud in the hole.

(4) To form the mud protection wall, measure the sand content of the mud in the tunnel in time. Take effective measures in time when the standard is exceeded.

(5)Low headroom rotary excavation rentalManufacturers share check the tightness of the drilling bottom cover after closing. If it is found that the cracks are large due to distortion, they should be repaired in time to avoid sand leakage.