Study Of Friction And Torque In Trenchless Guide Drilling

Trenchless technique is used for detecting, checking, renovating,changing and laying all sorts of underground pipeline facilities when theground surface isn't excavated. In the end of 1970s, guide drillingtechnique, ramming pipe method etc had been introduced into china. Thosetrenchless techniques introduced have promoted its using in our country.The construction of basic facilities in our country has flourished recently.So the engineering relating to trenchless technique are much more. Andthere has been promoted the developing of trenchless technique, especiallythe trenchless guide drilling technique. Compared with the others, thetrenchless guide drilling technique has many advantages: the disturbance tothe ground surface is much smaller, the accuracy and speed of constructionis much higher, its adaptability to the layers and circumstances is muchbetter, and the direction can be controlled when laying pipe. So it developsrapidly.Friction, back-pulling and torque is the two crucial factors whichdetermine the capacities of the driller in trenchless drilling. In order toselect the equipments, design and determine the construction schemeproperly, we should analyze and forecast the two factors detailed andaccurately. At the present time, there are experience and analog methods todetermine the two indexes, so it is necessary to research in theory.The research of friction and torque in trenchless guide drilling relate tothe bore-hole's trace. The formats of its trace are various. The mostcommon format is tangential path-curve path-tangential path-curve path-tangential path. According to the known conditions, mathematic methodsare used for the design of the trace in this article. According to the characteristic of the trenchless guide drilling, wecombine the different position of the drilling's trace, create the properfrictional resistance and moment of torque calculation model. We considerthe influence of the rigidity of the drill-stem when establish the model, itmeans that we consider the flexural torque and shear when establish themodel. In order to resolve easily we often use analytic equation whenmodel calculation. When we seek the frictional resistance and moment of torque ofnon-excavation guide drilling, we often use iteration. So we should knowthe stress condition of drill, to gain the axis force and moment of torque oflower face of unit cylinder, so we can gain the frictional resistance andmoment of torque of the all drill cylinder. The types of drill bit are various, drilling methods and drillingtechnologies are different, so as the failure mechanism of rock and soilmass. The drill bit used for trenchless guide drilling has unsymmetricalincline. It can form straight hole when rotary drilling, and form curve pathbecause the drill bit lean along the reverse direction of incline when drillingdirectly. The failure mechanism of rock and soil mass is relatively complex,and there are fewer people have researched. This problem is discussed inthe article. According to analyze the drilling process, the soil mass which contactto the drill bit's incline is destroyed and contact to the drill bit's back isn'tdestroyed when rotary drilling. It can form a straight hole. However, thesoil mass which contact to the drill bit's incline isn't destroyed and contactto the drill bit's back is destroyed when drilling directly. So the drill bit leanalong the reverse direction of incline when drilling directly. The soil massunder the drill bit is destroyed because of in compression conditions eitherrotary drilling or drilling directly. The drill bit's stress calculates accordingto the method which determines the limit bearing capacity of foundation. The different drilling methods are considered, we assume the limitingequilibrium condition of the drill, and create the corresponding mechanicsmodel. The back-pulling of pipeline is a very important parameter ofnon-excavation steering drill. The key to calculate the back-pulling is todetermine the force between the pipelines of the soil mass. So we can usefriction law to calculate the back-pulling of pipeline. To calculate the back-pulling pipeline, we presume that upper soilbody slumps after pipeline enter bore-hole,so arc-balance theory ofProtodrakonov or Terzaghi pressure calculate of loose volume is adopted tocalculate the effort on the pipeline。To calculate the effort acted bypipeline sides soil body to pipeline,Rankine active soil pressure theory isadopted。The action of low pipeline is the sum action by soil in slumpingarc and the weight of pipeline itself。To circle pipeline,for convenience ,it is considered as square section。So mechanics model of back-pullingpipeline is established。 Analyzing the trenchless guide drilling, there are many factors affect...