DTH Hammer Research Articles

Understanding effects from overburden drilling of piles—a rational approach to reduce the impacts on the surroundings

This paper presents two case studies dealing with undesirable impacts of overburden drilling of casings for end-bearing piles to bedrock. Monitored pore-water pressures and ground settlements are used to document and assess the influence from rotary percussive drilling with “down-the-hole” (DTH) hammers. The studies show that drilling with high-pressure air-driven DTH hammers may cause considerable erosion and soil volume loss adjacent to the drill bit and along the casing, resulting in settlements of the surrounding ground. The risk of soil volume loss increases when the drilling is carried out in erodible soils such as silt and fine sands. The volume loss is found to be caused by a combined air-lift pump effect and a Venturi suction effect. Monitoring pore pressures in the vicinity of the drilling may be used to reduce soil volume loss and prevent damaging settlements. Results from drilling with water-driven DTH hammer showed significantly less ground settlements and influence on pore pressures compared to using an air-driven hammer. The study suggests that the drilling parameters flow rate and penetration rate, and the cross-sectional area of the pile casing can be combined in a non-dimensional methodology to assess the mass balance of drill cuttings when drilling with water flushing. A design framework is suggested to guide overburden drilling in urban settings to reduce potential impact on the surroundings.

Impact Characteristics of a Bidirectional Pneumatic DTH Hammer for Unconsolidated Formations

With advantages of high efficiency and low cost, DTH hammer drilling has been highly applied in various drilling projects. When drilling in unconsolidated formations, it is prone to drilling accidents such as drilling tools sticking or burying. Thus, a bidirectional pneumatic DTH hammer is designed to drill boreholes using forward impact and release sticking drilling tools using backward impact. With a floating gas distribution mechanism, impact strokes of the DTH hammer piston can be changed when flat keys are in a different position of the key grooves on the gas distribution shaft. In drilling mode, the piston has a larger impact stroke and can impact the anvil at high speeds to drive the bit breaking rocks. When drilling tools become stuck, by changing to a smaller impact stroke, the piston can impact backward on the gas distribution valve to break rocks above the DTH hammer so sticking drilling tools can be released. According to the structure and working principle of the bidirectional pneumatic DTH hammer, a physical model based on the pneumatic transmission circuit is established; then, a simulation model is built with pneumatic transmission module components in software of SimulationX 4.1 student version. Piston velocities, displacements, and impact energy are analyzed, with main factors including piston mass, total weight of the DTH hammer, compressed air pressure, and backward impact stroke being considered. Analysis results show that working characteristics of the DTH hammer are fairly affected by piston mass and compressed air pressure. Based on the changing laws of the impact frequency, peak of impact velocity, and impact energy, a piston mass of 18 kg, total weight of 125 kg, gas source pressure of 2.2 MPa, and lifting distance of 60 mm for backward impact were recommended. To verify the performance of the bidirectional pneumatic DTH hammer, field experiments were carried out in the gravel stratums. The bidirectional DTH hammer was in good working condition and the maximum drilling rate can reach up to 1.5 m/min. By lifting the DTH hammer away from the bottom of the borehole and pumping compressed air, the DTH hammer piston could achieve a high frequency backward impact. There are no drilling tools’ sticking or burying accidents in the drilling experiments. The bidirectional pneumatic DTH hammer can effectively drill boreholes in loose formations and deal with drilling tools’ sticking or burying accidents.

Analysis of the dynamic response and impact parameters of pneumatic down-the-hole hammer drilling rescue holes

The utilization of pneumatic DTH hammer drilling is the most efficient approach to rescue miners. The previous DTH hammer's impact model was simplified and the analysis of impact parameters was incomplete, hindering further drilling research. To enhance the rate of penetration (ROP) in downhole rescue drilling, this paper establishes a dynamics model for single impact drilling using a pneumatic DTH hammer. The model considers stress wave transmission between flexible components and derives response functions for the piston and drill bit. Through numerical simulation combined with engineering, the velocity-displacement response of the drill bit's bottom in the time and frequency domains is obtained. The effect of impact parameters on the displacement, velocity responses, and stress distribution of the piston and bit during impact is analysed. The results show that weight on bit has a large effect on the quasi-static response, and only focusing on vibration can ignore the static effect. The maximum value of the ROP occurs at the instant of impact, and its corresponding frequency represents the optimal impact frequency. These provide a theoretical reference for achieving higher construction speeds, greatly shortening the duration of mine accident rescue operations, and ensuring the safety of personnel trapped underground.

Energy efficiency evaluation of high-pressure DTH hammers

The design of a domestically produced DTH hammer for drilling holes in rocks of medium and high strength is presented. Using the mathematical modeling method, the serviceability of the hammer at an energy source pressure of 2.4 MPa is proved. The results of DTH hammer prototype testing at lab and full scale are presented.

Fluidic DTH hammer with backward-impact-damping design for hard rock drilling

Hard rock drilling is increasingly important due to progress in both the use of geothermal heat as a new energy source and the development of new unconventional gas fields. The DTH hammer drilling method is generally considered one of the best approaches for drilling hard rocks. A fluidic DTH hammer with backward-impact-damping design for hard rock drilling was proposed in the study. Striking features of this DTH hammer tool include extended life expectancy and capability to withstand drilling fluids solids content. A sequence of numerical and experimental investigations were performed on the newly designed fluidic DTH hammer. It is observed that the backward-impact-damping design is effective in protecting the fluidic oscillator from damage. Although the backward-impact-damping design may cause a decrease in the single-impact energy, the increased impact frequency can offset the aforementioned disadvantage to a certain extent. The paper brings attention to several interesting aspects of the fluidic DTH hammer. The accumulated data provide useful information to develop this type of a DTH hammer and facilitate its popularization and application in hard rock drilling.

Analysis on structural design and experimental effect of two kinds of hollow- through DTH hammer reverse circulation bits

Analysis on structural design and experimental effect of two kinds of hollow- through DTH hammer reverse circulation bits

Influence of DTH Hammer Impact Energy on Drilling-with-Casing System Performance

Water well drilling-with-casing equipment is described in the article. Construction diagrams and field test results of series-production and new drilling-with-casing DTH hammers possessing higher impact energy are analyzed. The economic study of water well drilling cost in geological conditions of the Republic of Altai is performed.

КОМПЬЮТЕРНОЕ МОДЕЛИРОВАНИЕ РАБОЧЕГО ПРОЦЕССА ПОГРУЖНОГО ПНЕВМОУДАРНИКА П-110

КОМПЬЮТЕРНОЕ МОДЕЛИРОВАНИЕ РАБОЧЕГО ПРОЦЕССА ПОГРУЖНОГО ПНЕВМОУДАРНИКА П-110

Influence of DTH Hammer Impact Energy on Drilling-with-Casing System Performance

Influence of DTH Hammer Impact Energy on Drilling-with-Casing System Performance

Study on the abrasion property of the anvil inside a hydraulic DTH hammer fitted with horizontal oriented sliders

Hydraulic hammers have been extensively applied to horizontal directional well drilling in hard rock formations. However, the service life of a hydraulic hammer is still unsatisfactory due to the heavy wear or abrasion of the horizontal anvil, which leads to the failure and the reduction of service life in directional well drilling. In order to improve the performance life of a hydraulic hammer, the new type of anvil with a horizontal oriented slider has been designed. The abrasion property of the horizontal oriented slider have been numerically simulated and analyzed by Finite Element Analysis. Simulation and experimental results have shown that the abrasion rate exponentially varies with the mass of the anvil and the friction coefficient of horizontal oriented slider, nevertheless the abrasion rate of horizontal anvil is almost logarithmically varies with moving velocity of oriented slider. The maximum abrasion rate of horizontal oriented sliders will exceed 4% while moving velocity of the horizontal anvil is larger than 3m/s. While the mass of the anvil is 100kg, the maximum abrasion rate of horizontal oriented slider is 7.5?. However, the maximum abrasion rate of a horizontal oriented slider will be up to 16.5% while the friction coefficient is more than 0.2.

Vertical section construction of wells at Kuyumbinsky oil field via percussive-rotary drilling with DTH hammer.

The article presents the analysis of sequential use of mobile percussive-rotary drilling sets with DTH hammer and bottom-hole cleaning by foam mud in construction of vertical sections along with at Kuyumbinsky oil field. On the basis of the analysis, an engineering solution is proposed to prevent disastrous mud loss that is the key factor of efficiency in implementation of resource-saving technologies.

다운더홀(DTH) 해머의 모델링 및 실험

Research and development of mineral resource related products has progressed with the increased need to develop mineral resources. The DTH hammer is one a resultant product. However, due to particular work conditions of underground drilling, it is difficult to obtain direct data on the DTH Hammer. A DTH drill rig requires a lot of money and time for actual testing. This thesis aimed to resolve this problem by using CAE. First, the structure of the DTH hammer and the movement was analyzed. Next, a standard model based on simulation was proposed and then experimentation and comparison verification was conducted. In addition, the verified models were applied to products of various sizes, and the models used in simulation were compared by conducting field tests.

栾川钼矿复杂地层钻进跟管钻具研制

栾川钼矿地层是典型的硬、脆、碎、塌复杂地层，特别是上部地层尤其破碎，勘探时采用跟管钻进保护孔壁。但跟管钻进过程中，遇到了岩样采取率低、跟管管靴断裂、跟管深度不足等技术难题。为解决所遇问题，研发了反循环潜孔锤同心跟管钻进钻具；利用ANSYS有限元软件对套管管靴结构参数进行了仿真分析研究，优化了管靴结构，提高了管靴使用寿命，提高跟管深度。 The stratum of molybdenum minerals in Luanchuan, especially the upper strata is a typical hard, brittle, broken, and collapsed formation. The experiment shows drilling with casing in this area low core recovery rate, casing shoe fractured easily, depth and other technical problem. In order to solve these problems encountered, concentric casing drilling bit of reverse circulation DTH hammer is designed, simulation analysis of casing shoe structure is also made by finite element software (ANSYS), the structure of casing shoe is optimized, the service life of casing shoe is improved, the depth of drilling casing is increased.

The Combined Guiding Hole Technology of Large Diameter DTH Hammer and Long Screw-Pile Driver

From an engineering reality, in order to solve complex stratigraphic drilling problems and improve construction efficiency, the method of combination of large diameter DTH hammer and the pile driver with a special long spiral drill multifunctional is proposed. This method has the characteristics of simple equipment, fast, effective, low cost etc. It can quickly drill through layers of gravel, stone, weathered bedrock, reach to depth up to above 25m. It has been widely used in embedded engineering methods of precast piles, the long spiral rock-socketed piles, piles into the rock currently. The study of this construction method has not only wide range of applications, but also has a wide range of practical and theoretical significance.

The Combined Guiding Hole Technology of Large Diameter DTH Hammer and Long Screw-Pile Driver

From an engineering reality, in order to solve complex stratigraphic drilling problems and improve construction efficiency, the method of combination of large diameter DTH hammer and the pile driver with a special long spiral drill multifunctional is proposed. This method has the characteristics of simple equipment, fast, effective, low cost etc. It can quickly drill through layers of gravel, stone, weathered bedrock, reach to depth up to above 25m. It has been widely used in embedded engineering methods of precast piles, the long spiral rock-socketed piles, piles into the rock currently. The study of this construction method has not only wide range of applications, but also has a wide range of practical and theoretical significance.

The Computerized Simulation Software Development of the Bidirectional Pneumatic Hammer

During the construction for solving geological hazard of landslide, there often existed the accidents of sticking pipe and burying drilling caused by borehole collapse. It resulted that drilling tool couldn’t be pulled out, and scraped the drilling tool and borehole. So it was necessary to research a kind of pneumatic hammer which could realize drilling at normal work, and push out the drilling tool by reverse impact when the formation collapse caused sticking pipe and bury drilling. In order to research profoundly the pneumatic hammer work mechanism and describe piston movement laws in detail, physical model was established according to the actual conditions, finite difference method was adopted, thermodynamics and kinematics were applied. Using object-oriented programming, the bidirectional pneumatic hammer software was developed whose integrated development environment was VB. The software could calculate acceleration, velocity, displacement, pressure, temperature of the front and back air chamber at any time and the operating performance parameters of the pneumatic hammer. Not only the bidirectional pneumatic hammer, but also the unidirectional pneumatic DTH hammer and the no-dig impactor were designed by the software.

Research on diamond-enhanced tungsten carbide composite button bits

At the present time in China, the cutters used in button bits and rock bits are mainly cobalt tungsten carbide. Because of its low abrasive resistance, the bit service life and drilling efficiency are very low when hard and extremely hard formations are being drilled. Owing to its high abrasive resistance, diamond composite material is widely used in drilling operations. However, its toughness against impact is too low to be used in percussion drilling, so it can only be used in rotary drilling. In order to solve the problems encountered by the DTH hammer in hard rock drilling, to increase the life of the bit, to increase the rate of penetration and to decrease drilling cost, a new type of diamond-enhanced tungsten carbide composite button with high abrasive resistance and high toughness against impact, which may be used in percussion drilling, has been developed. The key problems in making the button are to improve the thermal stability of the diamond, increase the welding strength between the diamond and the cemented tungsten carbide, and reduce the sintering temperature of the tungsten carbide. All these problems have been solved effectively by pretreatment of the diamond, low temperature activation hot-press sintering, and high sintering pressure. The properties of the button have been determined under laboratory conditions. The test results show that its hardness is more than 86 HRA, its abrasiveness resistance is 100 times more than that of conventional cemented tungsten carbide, and its toughness against impact is more than 100 J. All these data theoretically that show the button has very good mechanical properties that can meet the needs of percussion drilling, and can solve the problems encountered with button bits of conventional cemented tungsten carbide.