Research On The Drill Pipe Force Transmission Characteristics Of Drilling In Soft Coal Seam

Occurrence of stuck and broken drills caused by blocked slagging channels during drilling of soft coal seams is also the main reason for "short drilling,low efficiency,and many accidents" during drilling.In this paper,the drill pipe is used as the research object,and the combination of theoretical analysis,numerical simulation,and laboratory test research is used to study the shape and force characteristics of the drill pipe in the borehole.Drilling is divided into two cases: normal drilling and hole plugging.The change law of drill rod torque and thrust during hole plugging and hole collapse during drilling is studied.Intelligent identification relationships provide theoretical support.The drill pipe during normal drilling is divided into a suspended section and a bottomed section.In the suspended section,the drill pipe is only affected by the frictional force given by the slag in the slag discharge space.In the bottoming section,the drill pipe is not only affected by the frictional force given by the slag in the slag discharge space,but also by the frictional force caused by the contact with the hole wall.Through quantitative analysis,the torque and thrust loss of the drill pipe per unit length in the bottoming section is 1-3 times that of the suspended section.According to the principle of drilling plugging,drilling plugging is divided into block plugging and collapsing plugging.List the corresponding drill pipe force equations based on the characteristics of plugging and collapse.Quantitative analysis is made by taking the existence of a collapsing hole as an example.For a drill pipe of ? =63.5mm,the torque loss of the blocked section is 2.76 times that of the bottomed section and the thrust loss is 2.35 times that of the bottomed section.The torque loss of the drill pipe and the blocked section is 2.13 times that of the bottomed section,and the thrust loss of the blocked section is 2.08 times that of the bottomed section.A simulated material with a Platts coefficient of 0.36 was used to simulate soft coal seams for laboratory tests.Comparing the data obtained from the test with the theoretical calculation results,the difference between the theoretical calculation results and the laboratory test results is about 11%,which verifies the correctness of the theoretical calculation formulas and provides a theoretical reference for the intelligent drilling of the hydraulic rig.