Design Study On The Head's Deflection Controlling Mechanism Of KCM-130Ⅱ Type Steerable Impact Mole

The traditional constructing method of installing pipe by digging is widelyopposed due to affecting traffic, polluting the environment and bringing muchinconvenience to people's daily life. In addition, digging shrivels where it isimpossible or forbidden to dig. Under this situation, a technological revolutioncame into the construction field of pipeline engineering—that's trenchlesstechnology or No-dig technology.Impact moling is one of the construction methods of installing pipeline bytrenchless technology which was used earlier and more widely. As thismethod has many advantages, such as quick installing pipe, simpleequipment, easy operation and maintenance, low investment for equipmentsand low construction cost and so on, it is being widely used for installing shortshallow minor diameter pipeline underground. But the boring direction of thecommon impact mole can't be controlled and the accuracy of installingpipeline is low. Also, it will depart from design direction or even lostunderground when meeting with some obstacles. Due to these limits, thecommon impact moles cannot meet the demand of more and more curvilinearpipeline installing projects. Therefore, the steerable impact mole whoseboring direction can be controlled and underground position and boring posecan be monitored will become the developing trend of impact mole.With more and more short minor diameter pipelines to be installed shallowlyunderground, streerable impact mole technology would be used broadly.However, because of its imperfect aspects, contractors have been puttingtheir attention to directional drilling mini-rig which has high mechanization,automatization and preeminent performance. Directional drilling asks forequipments of high qualities and operators with professional skills. The greatand costly equipments for directional drilling need aborative and expensivemaintaince. The recoil is big during the drilling. In addition, the drilling fluidused in the dirlling will pollute the environment.Steerable impact moling technology, which combines impact molingtechnology with directional drilling technology, needn't drilling rig, drill stemand drilling fluid. Steerable impact mole has simple structure and low cost andis easy to operate and maintain. It can drill curvilinear bore, so the accuracy ofinstalling pipeline is much higher. Successfull steerable impact mole willsubstitute for directional drilling mini-rig and give a challenge to its market.Consequently, some impact mole factories and scientific researchorganizations all over the world have been developing the steerable impactmole. But there has been no perfect products so far.KCM-130Ⅰ type steerable impact mole is the momentous achievement ofscientific research project assumed by our college from the ministry of landand resources P.R.C during the ninth five-year plan. It had been tested thatthe mole could drill curvilinear bore. Its percussion mechanism works stablyand reliably. Also this mechanism can strike backwards so as to make themole back. The mole of simple structure is easy to operate. But it still hassome fateful drawbacks, for example, the head can't be locked and theshifting shaft is easy to rupture, which invalidate the head's deflectioncontrolling mechanism. Therefore, the operator can't control the head'sdeflection accurately. Besides, the tracking system hasn't been applied to themole so that the operator can't monitor the mole's underground position andits boring pose.The author studies on the shortcomings and defects of KCM-130Ⅰ typesteerable impact mole which are mentioned above. Although the theoreticaland experimental studies on the steerable impact mole haven't been deeplytaken, such as studies on interaction mechanism between the impact moleand the earth and the affecting factors of the boring track, the author holdsthat the faultiness of the steerable impact mole's structure and functionrestricts extent and deepness of the theoretical and experimental studies. Sothe author stresses on the structural design and functional perfecting firstly.Therefore, the author improves, optimizes and designs the head's deflectioncontrolling mechanism and some accessorial mechanisms on the base ofKCM-130Ⅰ type steerable impact mole's structure. The concrete researchesare as follows:1. The head's deflection controlling mechanism, on which the head'sdeflection's adjusting and the boring track's controlling are relying, is one ofthe most pivotal mechanisms of steerable impact mole. However, owing to thedefects on the structural design, the head could rotate together with theshifting shaft around the axis of the later automatically by exogenic action,which changes the head's deflection unartificially and keeps the headhalf-controlled. Therefore, the author analyses the work principle andmovement law of the head's deflection controlling mechanism. The reasonwhy the head can't be locked is found. And then the author raises the threadto resolve this problem. Also the author improves the head's deflectioncontrolling mechanism and designs the head locking mechanism whichconfines the rotation of the shifting shaft by two clamp plates.2. The shifting shaft is one of the key parts of the head's deflectioncontrolling mechanism, by which the deflection angle and the roll angle arecontrolled, the head is connected with the mole's body and nearly all thedeflection moment the head received is assumed. The movement law of theshifting shaft is complex, and the stress and restriction conditions are rigorous.The shifting shaft ruptured in the outdoor test, which separated the head fromthe body and made the head's deflection controlling mechanism invalid. Theauthor designs an assistant loading mechanism of the shifting shaft—a lug onthe right clamp plate, which is infixed the slot behind the head. The lug bearsthe deflection moment together with the shifting shaft, so the stressingcondition of the shifting shaft is improved. The author has designed two kindsof assistant loading mechanisms—one-way loading mechanism and both-wayloading mechanism. The work principle and their features are analyzed andcompared. At last, the both-way loading mechanism is selected to use inKCM-130Ⅱ type steerable impact mole;In addition, the stress and restriction conditions of the shifting shaft areanalyzed. Also the finite element static analysis is made by ANSYS softwareto visualize the distributing of stress and displacement in the shifting shaft.Through observing the fracture and associating with the stressingcharacteristic, we can make certain that the rupture should be fatigue failure.As long as the stress level of the shifting shaft is reduced to a given degree,its fatigue life can be increased greatly. Therefore, the author improves andoptimizes the structure of the shifting shaft in many ways, for example,enlarging the radial dimension, canceling the tool recess and shifting thethreaded portion and so on. All these measures are to avoid stressconcentration or decrease the degree of stress concentration by avoidingmutational shape and size. To validate the result of optimization, finiteelement static analysis is made on the shifting shaft by ANSYS software. Theanalysis results of improved model are compared with the primary model'sanalysis results. The author also makes finite element static analysis on themodel of the shifting shaft after the assistant loading mechanism is designed.Also the analysis results are compared with the primary model's analysisresults.3. In the working process of the impact mole, the core pipe will vibratestrenuously alone the axis of the mole body by the action of both the imactforce produced when the piston is striking the anvil and the resilience of thespring in the core pipe draging mechanism. If the vibration amplitude of thecore pipe is excessive,it is possible that the lug in front of the right clampplate exits from the slot behind the head. If the shifting shaft deforms byexogenic action, the clamp plates and the core pipe may be unable to return,which may invalidate the assistant loading mechanism of the shifting shaft. Atthis time, the shifting shaft will bear the deflection moment of the head alone.Therefore, it's necessary to design a location limiting mechanism to limit theamplitude of vibration. Borrowing ideas from the structure and work principleof the spring chuck locating mechanism of the wire-line coring drilling tool, theauthor designs a spring chuck location limiting mechanism to limit the axialdisplacement amplitude of the core pipe. Two kinds of spring chuck locationlimiting mechanisms have been designed one after the other. On the basis ofanalysis of their respective features and defects, the author chooses to mountthe spring chuck on the pulling loop and relieve the clamping by the individualclamp relieving apparatus.4. Data sonde is the "eye" of the steerable impact mole. If we want tocontrol the boring track to tally with the planned track, we should use thetracking system to monitor the mole's underground position and the head'sdeflection. Because there is no data sonde—transmitter on KCM-130Ⅰ typesteerable impact mole, we cannot monitor the mole. The author selects thesonde and its mounting position and designs structure of the sonde housing.The Subsite750 type tracking system is applied to KCM-130Ⅱ type steerableimpact mole. Thus we can monitor the mole's underground position and thehead's deflection.Owing to the particularity of the head's deflection controlling mechanism ofKCM-130Ⅱ type steerable impact mole, it is not one-to-one correspondenceamong the receiver's clock indication of the tracking system and the head'sdeflection angle and roll angle. Therefore, associating with the process ofadjusting the head's deflection in practice, the author preliminarily studies onhow to determine the head's deflection angle and roll angle through thereceiver's clock indication of the tracking system. The connection betweenthem and the practical operation methods are also put forward.Although the research production mentioned above hasn't been tested, theauthor simulates and analyses them by SolidWorks and ANSYS software oncomputer. It's indicated by the simulation results that the head lockingmechanism, the assistant loading mechanism of the shifting shaft and thespring chuck location limiting mechanism can work well and fulfill theirfunction. Also the loading condition of the shifting shaft is improved clearly. It'sprevious that the structure designs mentioned above are effective approachesto solving the problems of KCM-130Ⅰ type steerable impact mole, forexample, the head can't be locked and the shifting shaft is easy to rupture. Inaddition, the author applies the tracking system to KCM-130Ⅱ type steerableimpact mole and puts forward the method of how to determine the head'sdeflection through the receiver's clock indication associating with the practicaloperation process. These theoretical studies will give much thinking andreference value for the continuous research on the steerable impact mole.To sum up, through the studies mentioned above, the structure and functionof KCM-130Ⅱ type steerable impact mole are improved, which will promoteits practical application and lay consistent foundation to enter product market.Certainly, these designs and theoretical studies need many tests to validatetheir feasibility and reliability so that we can improve the mole in succession.