Differences between Rotary Drilling Rigs, Percussive Reverse Circulation Drilling Rigs And Reverse Circulation Rotary Drilling Rigs

Rotary drilling hole filling pile, also known as positive and negative circulation hole filling pile, is the most commonly used and widely applied pile forming method in China, which is to use general geological drilling rigs under the condition of mud wall protection, slow drilling, slagging through mud to form holes, and filling concrete to form piles.

   Its characteristics are: can use the geological department conventional geological drilling rig, can be used for a variety of geological conditions, a variety of sizes of holes (300mm ~ 200mm) and depth (40m ~ 100m), the wall effect is good, the quality of the hole is reliable; construction without noise, no vibration, no extrusion; tools and equipment is simple, easy to operate, the cost is relatively low, but slow speed of holes, low efficiency, water consumption water consumption is large, slurry discharge However, the hole formation speed is slow, efficiency is low, water consumption is large, mud emission is large and pollutes the environment, and the reaming rate is difficult to control. It is suitable for application in high-rise buildings, soft and hard soil layers with high water table, such as silt, clayey soil, sandy soil, soft rock and other soil layers. According to the construction projects, different strata, different areas but the same drilling caliber to compare, found that the impact of reverse circulation and rotary circulation each has its own advantages, generally in the clay, sub-clay, silty soil layer, silt layer Construction, through the drilling record statement, take the average data analysis, rotary drilling rig than the impact of the reverse circulation drilling rig construction faster than 1.2 times, and due to the heavy weight of the impact of reverse circulation drilling rig relocation difficulties, long time and other factors, the impact of the reverse circulation drilling rig is difficult to control the water level, such as the application of soft rock, soft rock and other soft soil. However, in the construction of pebble gravel layer and bedrock, the percussion reverse circulation drilling is obviously 3 times faster than the rotary drilling rig, generally 2 times faster than the gravel below 5cm, and 3 times faster than the gravel from 5cm to 10cm, and the percussion reverse circulation drilling is 5-6 times faster than the rotary drilling in the rock below 5 levels. From the above analysis, impact reverse circulation has obvious advantages in the construction of complex strata, i.e., pebble layer, rock-embedded drilling piles, especially in some hilly and mountainous areas, the superiority is even more significant.

For the pile hole molding, impact reverse circulation construction hole diameter is generally in the clay, sub-clay, silty soil layer, silt layer, silt layer construction in order to prevent the collapse of the hole, still use the positive cycle of percussive drilling, but easy to shrink the diameter, but the verticality of the pile is relatively good. In the pebble, gravel layer construction are used impact reverse circulation drilling, due to the impact force is larger, easy to collapse holes, filling coefficient is on the large side, according to Nanjing Infinity Engineering Equipment Co., Ltd. has been constructed a few engineering data show that in the rotary drilling rig into the section of the average filling coefficient of 1.15; and the impact of the reverse circulation drilling section of the filling coefficient of 1.25, filling coefficient of the impact in the soil layer and rotary basically close to in 1: 1.

In terms of cost consumption: in clay, sub-clay, silty soil layer, silt layer construction, impact reverse circulation cost consumption than rotary drilling rig consumption, the main impact drilling rig power power, high power consumption. And then the wire rope consumption, due to impact rope consumption, its own weight, relocation and transportation costs, etc., but in the pebble, gravel layer, drifting stone, block stone, bedrock construction, impact drilling efficiency is high, and rotary drilling rig abrasive material consumption, drilling speed is slow, long cycle of holes, the cost of more than 5 times than the impact drilling, such as the encounter of large drifting stone, large block stone, hardness of granite rotary drill can not be drilled, only with the impact! Reverse circulation drilling rig to complete.

   In terms of environmental impact, impact reverse circulation drilling vibration on the surrounding environment than rotary drilling is greater, especially when the impact of the lower part of the hard foundation rock face, impact vibration on the surrounding sound, affecting people's rest.

   In conclusion, in the construction of the foundation, the selection of equipment is very important, for different strata of different construction techniques, from our years of experience in construction and the use of equipment, in the clay, sub-clay, silt soil layer, silt layer construction, the use of rotary drilling, its low cost, good quality holes, light weight, easy to relocate and other advantages of the more adapted; and in the pebble gravel, drifting stone, blocks, bedrock and so on. In pebble gravel, drifting stone, block stone, bedrock and other complex strata and old foundation treatment construction, the use of percussive reverse circulation drilling is more adaptable, because it can speed up the construction cycle, improve the efficiency of drilling, and ensure the quality of the project. Therefore, when we are constructing bored piles, we have to choose equipment and technology with scientific method according to the site conditions, schedule requirements, ground quality and cost analysis, and use the best construction technology to produce the best benefit under the condition of guaranteeing the quality, schedule and safety.

END