Combination of Jet Grouting Drilling Rig and Rotary Drilling Rig in Soft Soil Key Hole Forming Technology of cast-in-place pile in Rock Stratum

Combination of Jet Grouting Drilling Rig and Rotary Drilling Rig in Soft Soil Key Hole Forming Technology of cast-in-place pile in Rock Stratum

In order to give full play to the equipment technology of high automation integration of rotary drilling rig and ensure that the rotary drilling rig can smoothly pass through the weak soil layer and enter the rock stratum to form holes, the high-pressure jet grouting drilling rig is used to reinforce the weak soil layer around the bored pile, and then the rotary drilling rig is used to pass through the weak soil layer at the boring pile position and enter the rock stratum to form holes. The combination of jet grouting drilling rig and rotary drilling rig has high efficiency and low comprehensive cost in the construction of bored piles in soft soil and rock strata.

With the vigorous development of China's engineering construction, pile foundation has been widely used in large-scale projects such as bridges, ports, and high-rise buildings, and has become one of the most important basic forms in China's engineering construction. In particular, bored piles have become the most commonly used pile type in large-scale engineering foundations at home and abroad due to the use of mechanical drilling, no disturbance to the surrounding soil layer, high bearing capacity, strong adaptability, clear calculation of bearing capacity, etc., and pile diameter and pile length are also increasing.

Bored pile construction includes the following main steps: hole, steel cage production, and placement, hole cleaning, pouring concrete, and pile quality testing. Among them, the hole is the first step in bored pile construction. There are many mechanical equipment or methods for drilling, such as mechanical rotary drilling rigs, rotary drilling rigs, full rotary drilling rigs, full hydraulic drilling rigs, and manual excavation. Various mechanical equipment or methods have their own advantages and disadvantages.

Because of its simple operation, easy construction technology, low requirement for site bearing capacity, and low construction cost, a mechanical rotary drilling rig is usually used to drill holes in the soil. However, when encountering rock formations, limited by the torque of the mechanical rotary drilling rig and the hardness of the alloy cutting teeth, the machine rotary drilling rig passes through the rock formations with low efficiency or even cannot pass through. A rotary drilling rig has become a piece of common mechanical equipment for hole forming because of its high degree of automation, high hole forming efficiency, less environmental pollution, good adaptability to soil layer, rock layer, and comprehensive economy. However, a rotary drilling rig also has obvious disadvantages, such as large weight and high requirements for site bearing capacity.

For the combination of the overlying strata of the site as a soft soil layer and the underlying strata as a rock layer, the mechanical rotary drilling rig with low construction cost can pass through the soil layer, but it is impossible to pass through the rock layer to form a hole; if the comprehensive and economical rotary drilling rig is used, although it can cross the soil layer and rock layer to form holes, because the bearing capacity of the overlying soft soil layer is low, or the rotary drilling rig is not allowed to enter the site, it is naturally impossible for the rotary drilling rig to cross the soft soil layer and rock layer to form holes, or the rotary drilling rig can enter the site for construction. Under the weight of the rotary drilling rig, it may cause concrete waste caused by pile quality accidents such as shrinkage and collapse of bored piles or expansion. In geotechnical engineering, the combination of the soft soil layer and rock layer is very common. Therefore, without increasing the construction cost, it is a problem worthy of study to give full play to the advantages of hole-forming mechanical equipment and smoothly passing through the soft soil layer and rock layer.

Aiming at the requirements of efficient and economical hole-forming construction of cast-in-place pile in soft soil layer and rock stratum, a high-pressure jet grouting drill is used to reinforce the soft soil layer around the cast-in-place pile, and then a rotary drilling drill is used to cross the soft soil layer at the cast-in-place pile position and enter the rock stratum to form holes.

With the help of highly integrated automation equipment technology of rotary drilling rig, the combination of jet grouting drilling rig and rotary drilling rig can improve the construction efficiency and comprehensive cost of the bored pile in soft soil and rock stratum.