| Anchor strengthening technique has been an important branch of geotechnical engineering field. Ever since 1890, when this technique was used in an open pit shale mine of north wales of Britain, it has had a history of more than 100 years. Anchor strengthening is an active control measure , can fully mobilize the potential and energy of rock and soil mass and make full use of it, so as to strengthen the rock and soil mass and modify its properties in situ. Anchor strengthening technique has several advantages such as concise design method, simple construction, low cost, strong adaptability,little space occupation-beneficial to construction, and so on.Recent years, there are a lot of landslide geological hazards in highway construction and water conservancy and hydropower project. Because of the features such as loose , crushing , bad self-stability of rock and soil mass of the landslide formation, it is easily to collapse and even cause new landslide when encountering water, directly threaten the construction and normal use of highway and hydropower station. Therefore, it is necessary for us to carry out comprehensive treatment on it, so as to ensure the safety of the highway and hydropower station. In this field, the application of soil anchor is very wide. In the municipal construction field, when there are buildings or other municipal facilities, and no space for slope making of foundation pit excavation , anchor strengthening technique is usually to be used to maintain the stability of the foundation pit.Nowadays, in our country, the common construction methods that used for soil anchor pore-forming are flushing fluid normal circulation drilling and long helical dry work drilling. Flushing fluid normal circulation drilling is seldom been used. And long helical dry work drilling is not only high power consumption, high rotational speed, high abrasion of drilling tools, but also limited by the weight of the drilling tools, and hard to control the drilling dip—influence the quality of the project. In the loose soil formation, the efficiency of the vibratory drilling is quite high, and in the formation that composed of soil and stone, the pore-forming efficiency of percussive drilling is quite high, too. If the two are combined, and certain axial force and rotational force is given, the drilling efficiency will be promoted significantly. Considering that flushing fluid can't be used, so we can adopt air drilling. Integrate the advantages of the above methods, and then, the DTH impact compaction drilling method is formed.The advantages of percussive rotary impact compaction soil anchor are high drilling efficiency, good pore quality, simple equipment, low cost, high energy efficiency, and so on. But, there are several disadvantages:(1) This method can be only used in soil and sand formation;(2) There are still fall-block and hole shrinkage phenomena, that caused sticking and burying of drilling tools, and make it difficult to lift the drilling tools, and even that drilling tools can't be extracted out of the hole, influence the quality of the project.The purpose of developing JCM-130 pneumatic percussion mole is to improve the structure of the existing low pressure high energy pneumatic DTH hammer, make the adaptability of the percussive rotary impact compaction soil anchor pore forming construction technique much stronger, make pore forming quality better, promote the drilling efficiency, and reduce the accident incidence.There are no existing bidirectional pneumatic DTH that can carry out positive and negative impact. Qualitative analyses and simulating calculation indicate that, when the exhaust stroke of the back air chamber increased greatly, piston will impact backward in a larger terminal velocity. Therefore, we adopt computer simulation technique to study the inner dynamic process of DTH and factors and parameters that influence and limit the performance of DTH, optimize the design parameters, and have successfully developed the JCM-130 pneumatic percussion mole that can impact positively and negatively.Based on the study of many types of DTH home and abroad in detail, JCM-130 pneumatic percussion mole adopts valveless DTH, and has such advantages:(1) Cancel the complex gas distribution device, adopt the simple gas distribution passage to distribute gas, the gas path is short, so the gas pressure loss is low;(2) JCM-130 pneumatic percussion mole has only one moving part, so the structure is simple, easy for maintenance;(3) doing work by expansion of compressed gas, make the air consumption much lower.When the structure is confirmed, mechanics-mathematics model can be made, and simulation analysis can be carried out on it. After optimizing the parameters of the model, the structure parameters and gas distribution parameters can be confirmed. The key techniques are as follows:(1) The inlet, expansion(compression) and exhaust stroke of front and back gas chamber the proportion relationship between them are Scientificly confirmed;(2)The quality and effective action area of the piston are confirmed to ensure that in the low pressure condition the last impacting velocity of the piston can reach to an ideal value;(3) The proportion relationship between the piston quality and the bit quality , the proportion relationship between the piston size and the bit size are confirmed reasonably, and energy transfer efficiency is most greatly promoted;(4) Based on experimental study, bit structure and the tooth arrangement rule are reasonably confirmed, and the service life of the bit is prolonged effectively. With the economic trade globalization, one want to win in the increasingly fierce market competition, development cycle must be shortened, product quality must be promoted and flexible response to the market is required. Who put out new product, who win the market. Nevertheless, traditional design and manufacturing mode can't meet these requirementsTo design and check mechanical parts and carry out system dynamic simulation aided by computer has become to be a developing direction of mechanical design, and as a newly arisen high-tech, it has become to an important direction of computer application in the engineering field. The virtual prototype is an equivalent digital model based on computer aided design technique, that can replace the real physical prototype for evaluating and testing in virtual environment. This kind of"software model"can show us the appearance features, the structural characteristics, the physical properties and the kinetic laws of the products just as the real physical prototype. The integrated simulation environment that taking the virtual prototype as research subject, combined with the geometric modeling technology, the system simulation technology and the human-computer interaction technology so as to support virtual product design, is called virtual product developing environment. The virtual prototyping technology is a method that combined with multi-discipline, and taking the computer hardware and software system as main research tool for the virtual prototype digitalization design in the virtual product developing environment. The main advantages of the virtual prototyping technology are that it can shorten product development cycle, reduce the research cost and so on.To dynamicly simulate of JCM-130 pneumatic percussion mole based on the Virtual Prototype Technology, a mathematical model according to the structure of JCM-130 pneumatic percussion mole should be established. In the solid model environment, we can accurately definite the geometric structure and the physical attribute of every part, then make all of the parts have a correct assembly relationship by adding constraints reasonably, meanwhile, the related degrees of freedom of the moving parts are preserved. The virtual prototyping model established by this way keeps highly consistent with the real product both in structure and principle, and makes a necessary preparation for the further simulation analyses in virtual environment.The simulation analyses aiming at the virtual prototype of JCM-130 pneumatic percussion mole should be placed at a complete system, and considered the interaction of each component link of the system. The complete system should also include an air compressor, a bit and the action object—rock mass. Every parts of the comprehensive feedback control system of JCM-130 pneumatic percussion mole should be refined one by one, and establish mathematical models separately. Use the software SimulationX to build the simulation system of piston moving and inlet and exhaust condition of front and back gas chamber. The pressure of the air compressor is controlled by modifying its value in the software system. The impact structure is composed of a piston, a impact hammer and a bit, among them, the piston and the impact hammer is regard as a rigid coupling body that moving together and its motion range is limited by a stroke control lever. The main external force that act on the power piston are the pressure of the inner cylinder's upside and downside cavity, the viscous damping that comes from the piston motion and the elastic load caused by the volume compressibility of the working medium; the mentioned dynamic process is mathematically described by a double sides output rod power piston cylinder in the comprehensive simulation model. Besides, the reacting force of the rock is treated as external elastic load, and acts on the end of the impact structure with the motion damping of the bit.Carry out the dynamic simulation by change the working parameters and the structure parameters of the pneumatic percussion mole. Carry out simulation analyses of positive and negative impact separately, speed changing curve and impact force changing curve can be got from the simulation output result. According to the data that come from the simulation, the impact energy can be calculated, and according the peak value of the impact force got from the simulation, finite element analysis of the part can also be carried out. In the simulation system, the influence of the structure parameters to the performance the pneumatic percussion mole can be studied by changing their values. According the analysis conclusion, optimization target can be put forward.Using Solidworks build three-dimensional model, combined with the above analysis results, carry out finite element analyses of the key parts, to check its strength and deformation. The main content of finite element analyses on the parts (include piston, bit, gas distribution set) that bearing periodical impact load are: the larget stress and strain that caused by single impact, the fatigue analysis in the condition of periodical load, natural frequency and vibration analysis of the parts.After the design and analysis, engineering drawings were drawn, two prototypes were made, and adjustments had been done, and have been applied in construction. The application and dealing with accidents in hole prove that the pneumatic percussion mole is suitable for anchorage construction of all kinds of soil formation, and has many advantages such as strong adaptability, rapid construction speed, high quality, low cost. Compared with common grouting bolt construction method, work-efficiency can be promoted 1 to 3 times, construction quality can be quaranteed, construction cost and labour intensity can be reduced greatly.
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