How to operate rotary drilling rig in bored pile construction of backfill soil
This paper introduces the application of rotary drilling rig in bored pile construction of backfill soil. The working process of rotary drilling rig is more complex, and more attention is paid to it. If you look at this in a systematic way, I'm sure there will be a lot of new gains.
1. General situation of the project
A mountain City Viaduct Pile with a total of 40, the pile diameter is 1.8 meters, 18~35 meters long pile. The rock socketed pile foundation is adopted for the bridge foundation, and the pile foundation should be embedded in the weak weathered rock surface with a depth of more than 3 times the diameter of the pile. Geological description: the upper layer of 8~25 meters of backfill, it has 5 meters of undisturbed soil, and then under the rock. Hydrological situation description: groundwater type mainly for Quaternary loose rock pore water and bedrock network weathering fissure water, surface without obvious water supply, mainly by atmospheric precipitation recharge. The artificial fill layer has large thickness, continuous distribution in some areas, poor water content and good permeability, and the topography of the field is the ditch and ridge topography, which is beneficial to the discharge of groundwater. The net weathered fissure water is poor in the bedrock of the field.
2. Comparison and selection of construction schemes
(1) because of the pile in the original position ditch, artificial fill thick backfill excavation after stability is insufficient, and the pile is deep, if using artificial dig hole pile construction, there is a big security risk.
(2) according to geological and hydrological data, the backfill of the project is thick and the soil permeability is good, so it can not be made into holes by slurry wall protection, and it is not suitable for drilling holes in wet working machinery.
(3) according to the screw drill generally suitable for small diameter bored pile, because the pile diameter of the project is 1800mm, it is not suitable for auger drilling.
(4) according to the geological and hydrological conditions, the hole mechanical rotary machine is the most suitable engineering. It has advantages of fast pore forming speed, safe excavation and suitable for stratum without underground water. Its disadvantage is that it is easy to collapse in backfill and drilling in rock is slower. This project adopts XCMG XRS680 rotary drilling rig, the maximum drilling diameter is 2500mm, the maximum drilling depth is 105m, the maximum torque is 390KN.m, the maximum drilling speed is 7 ~ 18r/min, the rated power is 298Kw.
3, construction technology and technical parameters
3.1 construction preparation
Before construction, the site should be leveled, the sundries should be removed, and the surface planting and planting soft soil should be replaced to ensure the filling density of the drilling rig foundation, so as to avoid uneven subsidence; meanwhile, the drainage work of the work site should be done, and the temporary drainage ditch should be dug in the construction scope to ensure that the construction site is not stagnant.
3.2 pile location lofting
The official before drilling according to design drawings and coordinate with the Total Station Pier Pile Foundation Center and accurate release records, self-test after passing the inspection, to the Engineer in time.
3.3 buried protective cylinder
Before drilling, set up a strong, watertight steel protection cylinder, retaining tube high 1.5m, 1cm thick steel plate production, diameter larger than the design pile diameter 20cm, the top surface is about 30cm higher than the construction platform. Digging buried tube when the bottom shall be leveled, and then through the control of Pile Lofting, the hole center location marked on the bottom of the tube dipping into pits, find out the casing of the center position, with a cross line in the casing at the top or bottom, and then move the tube to tube center position coincidence heart at the same time with the drilling hole, with horizontal feet or hammer ball check, the vertical tube. Thereafter, the clay is symmetrically and evenly backfilled around the protecting cylinder, and layered and rammed, and the deflection of the protecting cylinder is prevented when tamping.
