The Analysis And Research On The Mechanism Of High-frequency Vibration And Rotary Drilling Technology

High-frequency vibration and rotary drilling technical , which is made use of combining high-frequency vibration, rotating force and pressure to cut-in soft rock or soil, and deepen drilling for drilling or other drilling works , named sonic drilling or vibro-drilling as well. There was no any other drilling technical can compare with it in drilling scope and effect, because of mixing high-frequency vibration with routine large torque in drilling. High-frequency vibration rotary drilling technical is a new method of drilling with the advantage of fast drilling and high quality coring, the project's researched results can be widely used in Chinese environmental geological survey, exploration drilling, shallow mineral resources exploration, geo-construction prospecting and other fields. With the acceleration of Chinese urban construction development, high-frequency vibration and rotary drilling provide more prospects for Chinese urban geological survey more strict requirements in the drilling process.This text analyses mechanism of high-frequency vibration and rotary drilling from the three aspects. First of all, it describes the breakdown modality in each layer and deducts the law of energy transmission with the react of high- frequency vibration. Secondly, it analyses the different breakdown modality in each layer and microscopic mechanism. Again, it makes use of ANASYS software to simulate drilling and analysis the result.High-frequency vibration drilling plus the high frequency low-impact energy on the carbide drill or diamond bit for drilling. The main application of the method on soft soil or rock and drilling mechanism vary: High-frequency vibration degrade cohesive force when drilling in the solum for cut down shear strength and speed up drilling efficiency of soil. High-frequency vibration cause"sand liquefaction"when drilling in sand for increase drilling efficiency. the rock internal elements are forced to vibrate that cause fatigue failure when drilling in the rock, also by axial steadypressure and rotation, thereby enhancing the efficiency of broken rock.At the process of high-frequency vibration drilling, the soil skeleton structure is damaged by high-frequency vibrate force. For Clay soil says, the alignment of water molecules is disrupted and weaken hydration water molecules became free water for lost molecular attraction , Therefore, Clay soil's shear strength is decreased for the grain of cohesive fore decreased. The soil in the vibration load cause subsidence of soil and cut in the rotary drilling in the process of efficiency is increased.In the vibration loads, excess pore water pressure increased and gradually accumulated in the over and again vibration loading, then pore water can't expulsion in time cause high sand pore water and gradually become dense, resulting in increased pore water pressureμ. Under the principle of effective stress, shear strength of sand:From this formula, you will find shear strength of the sand was zero that is completely lost strength, and similar liquid state when the pore water pressureμand normal stressσis the equal. Such liquidating phenomenon reduce friction between the sand of grains and vibration shear surface will appear cause sandy soil shearing strength quickly step down, accordingly in favor of drilling in sand.At the process of rock drilling, the mechanical vibration to bring about alternating loads by periodical loads for solum or rock. As the loads changes that is why solum or rock results alternate stress and alternate strain by time dependent. After sufficient stress or strain periodical working, soil or rock will be flawing as the cumulative damage and the propagation of crack form four phases by fragmente demolish (Figure 1):1. crack nucleation phase2. microcrack spread phase3. macroscopic cracking spread phase4. the final stage of fractureIt'profit to the spreading of rock crack and form major volume friability crush from the unsubstantial space where is the rock, thereby increasing the efficiency of rock breaking and increasing the drilling speed by impact force on the bit for short and large transient stress. At the same time, there is beneficial impact energy and impact stress wave propagation to rock from vibrator react some drilling pressure on the bit, also promote drilling. In addition, the impact of high-frequency vibrator to produce elements of rock internal oscillations Figure 1 crack spread phase cause rock crushing fatigue and reduce its dynamic load strength.By create finite element modeling for drilling model on the soil, this results increase 33.6 mm / min by compared with conventional drilling. Thus it's satisfied with request which the high rate of core in drilling for eliminate residual stress by high-frequency vibrate.Base on the analytic results of theory and model, this text designs top-drive head mechanism which come true impact, rotation and pressure for infeed. It's include high-frequency vibrator and drilling head and absorbing institution is used as bolted connections for vacuity working with the effect of drive-head. According to designing requirements, we design vibrator which is produce vibrating action by utilizing offcentering hummer's rotation bring about centrifgual force. Drilling head is drive by hydraulic motor which is come true stepless speed regulation. This drive head will be satisfy drilling requisition which is combine high-vibration with rotation, and also be ape to come true the optimization of drilling recommendation.By the research and analysis on the mechanism of high-frequency vibration rotary drilling technology, high-frequency vibration rotary drilling carry out high-performance drilling. It's a trend that combine high-frequency vibrate with rotary drilling in the future.