Grouting to Prevent Sulfate Corrosion on Coal Mine Shaft

Gang-Gang Xu,Shuan-Cheng Gu,Xiao-Dong Wang,Hai Wang,Shi-Bin Zhu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.11

In the area of high sulfate concentration in China, the problem of sulfate corrosion in coal mine shaft is increasingly prominent. Currently, shaft repair methods are limited to diversion, interception, and backwall grouting. However, after conventional cement stabilization, shafts still must contend with poor durability and weak resistance to sulfate corrosion. To solve these problems, this study combined theoretical research, laboratory tests, and field tests to reveal the corrosion mechanism of shafts, explored novel anti-sulfate corrosion grout, and built a model for the migration of sulfate ions (SO42−) in strata and shafts. According to the results of this study, shaft corrosion was a process of continuous penetration towards the concrete interior following a cycle of concrete compaction, expansion, and cracking. Laboratory tests show that the specimens of ordinary Portland cement mortar with 20 – 30% fly ash not only have good long-term strength, but also have a significantly improved resistance capacity to sulfate solution. Based on the laboratory test results, the HSR42.5 mixed with 20% fly ash was used for wall grouting, and the water-cement ratio of the slurry was 1:1. After wall grouting, the water inflow was effectively controlled in the grouting area in the main shaft, auxiliary shaft, and air shaft, reducing from 18.5 m3/h, 20.9 m3/h, and 10.0 m3/h to 3.5 m3/h, 4.6 m3/h, and 3.2 m3/h, respectively. Moreover, after nearly three years of continuous monitoring, the water inflow did not show any significant increase in the shafts. Based on the migration law of SO42− in concrete, a shaft geological model and a salt solution migration model after grouting reinforcement under sulfate corrosion conditions were constructed. In addition, the analysis of the migration law of sulfate ion in the shaft and grouting reinforcement formation revealed that the service period of the grouting shaft can be extended for approximately 6 – 8 years.

골프 샤프트 특성에 따른 드라이버 스윙 시 골프 볼의 역학적 구질과 인적특성과의 관계

최영철(Choi, Young-Chyul),김태완(Kim, Tae-Wan),심광보(Shim, Kwang-Bo),최봉암(Choi, Bong-Arm) 한국체육과학회 2016 한국체육과학회지 Vol.25 No.5

This study made measurements in terms of ten different kinds of 50g S shaft with different kick points using the VAS e valuation form a nd Trackman P ro t argeting 2 0 sub jects in t otal t hat consisted of 1 0 professional players of Korea Professional Golf Association (KPGA) and 10 professional players of Korea Ladies Professional Golf Association (KLPGA) in order to suggest the subjective assessment felt by professional golfers and the mechanical properties of golf balls, and as a result, the following conclusions were drawn: First, the degree of satisfaction felt by male professional players on the shaft currently in use was 8.30 point on average and at least 5.5 points and up to 6.8 points on the experimental shaft while, in the case of female professional players, the degree of satisfaction on the shaft currently in use was 7.56 point on average and at least 5.33 points and up to 6.78 points on experimental shaft. Second, the weight of the shaft currently being used by male professional players was 64.80g on average with the intensity of average X while the female professional players used 52g shaft with the intensity of average SR. The weight subjectively felt by male professional players per each shaft was at least 53.5g up to 63g while at least 53.89g and up to 57.78g for female players. Third, the mechanical property ( swing speed, b all speed, smash f actor, launch angle, height of b all and driving distance) of golf ball between the shafts at the driver swing by male professional players did not show statistically significant difference, however, in the case of female professional players, significant difference appeared in smash factor with p>.000, consequently, a post-hoc analysis followed, and it was revealed that an increase in smash factor was induced at the time of using the experimental shaft as could be seen from the results such as p>.047 with # 1, p>.022 with # 3, p>.006 with # 7, p> 0.018 with # 8, and p>.014 with #10 among the shafts currently in use and experimental shafts.

Rotary Shaft Structure Optimization of High-Temperature Motor Based on Ansys

Xi-fengWang,Da-weiMeng,ong-mingXu 보안공학연구지원센터 2015 International Journal of Smart Home Vol.9 No.5

This thesis focuses on the problems of high-temperature furnace motor in term of rotary shaft over length as well as deformation tendency under high-temperature condition, and therefore the thesis conducts design optimization upon rotary shaft of a motor that is applied in high-temperature furnace regarding its mechanical property and thermal-stress distribution. First, it establishes a full-scale 3D model of the shaft-fan system, then it analyzes its mechanical properties such as rigidity and stiffness under the high-temperature environment, which bases on reasonable assumed conditions and the boundary conditions, where hence the thesis puts forwards an optimized dimension design solution for the motor rotary shaft. And then the thesis analyzes and calculates the shaft-fan system to improve the motor shaft size from the angle of thermal stress and thermal deformation consideration and the special characteristics of such motor working under high-temperature environment. And the improved motor shaft size is verified as reasonable. The thesis analysis can be the designing references for cooling system applied in the high-temperature furnace motor.

Mechanism and force-energy parameters of a hollow shaft’s multi-wedge synchrostep cross-wedge rolling

Shuhua Zheng,Xuedao Shu,Sutao Han,Penghui Yu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

First, the rotation condition of a hollow shaft’s multi-wedge synchrostep cross-wedge rolling (MSCWR) is determined and the relevant influencing rule is illustrated based on a mechanical model of the hollow shaft and the theory of solid shaft’s rotation condition. The influence rule states that the increasing number of wedges increases the shrinkage rate of the hollow shaft and diminishes the rotation conditions, which can be improved by increasing μ on the forming surface of the hollow rolling mold, setting the stretching b , and forming α angles at approximately 4°-12° and 15°-35°, respectively. Second, a rigid-plastic finite element model is established for the hollow shaft with MSCWR by using the DEFORM-3D software, and the deformation mechanism of the hollow shaft is illustrated. The deformation degree of the rolling piece at the stretching stage decreases gradually from the surface to the interior of the hollow shaft, and radial compressive and transverse tensile strains interact with each other, thus resulting in an elliptic cross section of the hollow shaft. Stress field is mainly distributed in the exterior margin and then permeates into the inner part along the direction of the wall thickness, gradually transforming from compressive stress into tensile stress. Third, the influence of mechanical parameters on hollow shaft rolling is analyzed. The increased stretching angle increases the radial force, transverse force, and rolling torque and decreases the axial force. Moreover, the enlarged forming angle reduces the radial and transverse forces, while the decreased rolling torque increases the axial force. Finally, the 1:5 MSCWR experiment on the hollow shaft verifies the proposed finite element model’s accuracy. Results of the research provide a theoretical basis for the MSCWR of a precise hollow shaft.

골프 드라이버 샤프트의 가변성이 타구속도, 헤드스피드 및 비거리에 미치는 영향

정철(Chul Jung),박우영(Woo Yung Park) 한국유화학회 2018 한국응용과학기술학회지 Vol.35 No.1

이 연구의 목적은 골프드라이버 샤프트의 가변성이 타구속도, 헤드스피드 및 비거리에 미치는 영향을 분석하고자 하였다. 이 연구에 참여한 피검자는 핸디캡이 0인 남자 프로골퍼 10명과 핸디캡이 18인 남자 아마추어 골퍼 10명으로 하였다. 클럽의 종류는 1번 드라이버로 한정하였고, 각기 다른 스팩의 24개 드라이버를 가지고 실시하였다. 종속변인으로는 타구속도, 비거리 및 헤드스피드로 하였다. 연구 결과 다음과 같은 결과를 얻었다. 첫째, CPM에 따라 유의한 차이가 나는 것으로 밝혀졌고, 사후검증 후 230< 이상일 때 타구속도, 비거리 및 헤드스피드에서 최적의 수행력을 보였다. 둘째, 샤프트길이에 따른 타구속도 및 비거리는 유의한 차이가 나는 것으로 나타났고, 사후검증 후 타구속도 및 헤드스 피드는 46inch에서 비거리는 45inch에서 최적의 수행력을 보였다. 셋째, 샤프트 무게에 따른 변인 간 차이는 나지 않았고, 사후검증 후 샤프트 무게가 65g일 때 타구속도와 비거리에서 최적의 수행력을 보였 고, 50g일 때 헤드스피드에서 최적을 보였다. 또한 프로와 아마추어 간에는 변인에서 유의한 차이가 나는 것으로 나타났다. 결론적으로 최적의 드라이버는 CPM이 230<, 샤프트길이 46inch, 샤프트 무게가 65g 샤프트 일 때 최고의 수행력을 발휘하는 것으로 판명되었다. The purpose of this study is to analyze the optimum driver selection according to shaft intensity, shaft length and shaft weight that are determining factors of driver shot. To achieve the above purpose, the subject were participate with handicap zero 10 male pro golfer and mean score 90(handicap about 18) amateur 10 male golfer. The used club limited number 1 driver, we tested 24 driver which is shaft intensity, length, weight, total weight and swing weight. Dependent variable was strike ball speed, flying distance and head speed. The findings can be summarized as follows. First, There is a significantly difference in CPM. Ball speed, head speed and flying distance according to driver shaft intensity were found to be the best when CPM is 230<. Second, There is a significantly difference in shaft length. Ball speed, and head speed according to driver shaft length were found to be the best at 46 inch and flying distance were found to be the best at 45 inch. Third, There is not significantly difference in SW. Ball speed and flying distance according to driver shaft weight were found to be the best with 65g. In the case of head speed, it was the fastest with 50g shaft. Four, total variables were significantly difference between in pro and amateur golfer. In conclusion, there would be differences in individual physical condition but the best result was found with a driver of CPM 230<, shaft length 46inch, and shaft weight 65g.

Application of Fractography and Finite Element Analysis Adopting Elastic Foundation Stiffness to Improve Fatigue Life of Main Shaft in Mechanical Press

양원존(Won-Jon Yang),오충석(Chung-Seog Oh) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.5

The main shaft of a mechanical press inevitably includes significant stress concentrations that can trigger severe mechanical damage and finally lead to failure under repetitive use. In this study, an efficient procedure to quantitatively evaluate the fatigue life of the shaft system including the main shaft and its support bearings, based on the macroscopic failure analysis of the main shaft broken during actual use, was investigated. For this purpose, the bearing support was modeled as an elastic foundation, and the elastic foundation stiffness value was varied to determine the optimal value that best simulates the failure behavior, especially with respect to the failure location and failure sequence, of an actual shaft. While the finite element mesh size was kept the same, only the effect of elastic foundation stiffness was investigated. The optimum value for the main shaft investigated in this study was approximately 60 N/mm³, and the fatigue life of the shaft was evaluated based on the conventional maximum principal stress theory. Based on this, two modified designs to enhance the fatigue life of the existing shaft are proposed.

Magnetostrictive patch sensor system for battery-less real-time measurement of torsional vibrations of rotating shafts

Lee, Jun Kyu,Seung, Hong Min,Park, Chung Il,Lee, Joo Kyung,Lim, Do Hyeong,Kim, Yoon Young Elsevier 2018 Journal of Sound and Vibration Vol.414 No.-

<P><B>Abstract</B></P> <P>Real-time uninterrupted measurement for torsional vibrations of rotating shafts is crucial for permanent health monitoring. So far, strain gauge systems with telemetry units have been used for real-time monitoring. However, they have a critical disadvantage in that shaft operations must be stopped intermittently to replace telemetry unit batteries. To find an alternative method to carry out battery-less real-time measurement for torsional vibrations of rotating shafts, a magnetostrictive patch sensor system was proposed in the present study. Since the proposed sensor does not use any powered telemetry system, no battery is needed and thus there is no need to stop rotating shafts for battery replacement. The proposed sensor consists of magnetostrictive patches and small magnets tightly bonded onto a shaft. A solenoid coil is placed around the shaft to convert magnetostrictive patch deformation by shaft torsional vibration into electric voltage output. For sensor design and characterization, investigations were performed in a laboratory on relatively small-sized stationary solid shaft. A magnetostrictive patch sensor system was then designed and installed on a large rotating propulsion shaft of an LPG carrier ship in operation. Vibration signals were measured using the proposed sensor system and compared to those measured with a telemetry unit-equipped strain gauge system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A magnetostrictive torsional vibration sensor (MTVS) is proposed for shafts. </LI> <LI> The MTVS can measure torsional vibrations of rotating shafts without power supply. </LI> <LI> Torsional vibration is successfully measured in an LPG carrier ship by the MTVS. </LI> <LI> Its frequency spectrum is found to match well with that by a strain gauge. </LI> </UL> </P>

워터제트 추진기 임펠러 체결용 볼트파손 원인 분석 연구

정상진,오신일,허장욱 한국기계가공학회 2019 한국기계가공학회지 Vol.18 No.10

A water jet propeller is a key component that generates propulsion during the start of a naval vessel. When failure or breakage occurs, the vessel cannot operate. Recently, a flow analysis and structural analysis were conducted to understand the cause of damage to a bolt on a water jet. In particular, the stress and strain acting on the fastening bolt (impeller shaft and tail shaft) were examined to determine the extent of misalignment between the impeller shaft and the tail shaft of the water jet propeller. The study determined that stress and strain were concentrated on the impeller shaft and the tail shaft bolt. The alignment of the propeller impeller shaft and the tail shaft increased significantly in response to the tail shaft bolt. Failure of the tail shaft bolt fastening can lead to misalignment between the impeller shaft and the tail shaft.

GSI를 이용한 암반에 근입된 현장타설말뚝의 주면저항력 산정

조천환(Cho Chun Whan),이혁진(Lee Hyuk Jin) 대한토목학회 2006 대한토목학회논문집 C Vol.26 No.1

대부분의 설계지침서에서는 암반에 근입된 현장타설말뚝의 주면저항력을 산출하기 위하여 암석의 일축압축강도를 사용한다. 그러나 최근에 도로교 설계기준 해설(대한토목학회, 2001)과 AASHTO 설계지침서(2000)에서는 현장조건을 보다 잘 반영할 수 있도록 RQD를 적용하여 산출한 암반의 일축압축강도를 사용하도록 개정되었다. 그런데 RQD를 이용하여 암반의 일축압축강도를 산정하는 식을 국내의 주요 기반암에 적용하는 데에 문제가 제기되었고, 여기에는 RQD 자체의 문제점, 즉 지하수, 절리면 상태 등을 반영하지 못한다는 점도 포함되었다. 결국 도로교 설계기준 해설(2001)은 암석의 일축압축강도를 이용하여 주변저항력을 산정하는 방법으로 다시 개정되었다(한국도로공사, 2002). 본 연구에서는 암석의 일축압축강도와 현장 암반의 일축압축강도를 연관시키는 수단으로 제시되어 있는 기존의 여러 방법을 비교ㆍ검토하였으며, 이 가운데 신뢰도가 있는 것으로 평가되고 있는 Hoek-Brown 파괴 규준을 이용하여 암반의 일축압축강도 추정식을 제시하였다. 또한 이를 이용하여 암반에 근입된 현장타설말뚝의 주면저항력 예측 방법을 제안하였다. 제안된 방법은 현장타설말뚝의 재하시험 데이터를 이용하여 기존의 여러 방법으로 구한 주면저항력과 비교한 결과 신뢰도가 있음을 알 수 있었다. It is common to use the unconfined compressive strength (UCS) of intact rock to estimate the shaft resistance of rock socketed drilled shaft. Therefore the most design manuals give a guide to use the UCS of rock core to estimate the shaft resistance of rock-socketed drilled shaft. Recently, however the design manuals for highway bridge (KSCE, 2001) and of AASHTO (2000) were revised to use the DCS of rock mass with RQD instead of the UCS of rock core so that the estimated resistance could be representative of field conditions. Questions have been raised in application of the new guide to the domestic main bed rock types. The intrinsic drawbacks in terms of RQD were comprised in the questions, too. As the results, in 2002 the new guide in the design manual for highway bridge (KSCE, 2001) were again revised to use the UCS of rock core to estimate the shaft resistance of rock-socketed drilled shafts. In this paper, various methods which can estimate the UCS of rock mass from intact rock core were reviewed. It seems that among those, the Hoek-Brown method is very reliable and practical for the estimation of the UCS of rock mass from rock cores. As the results, using the Hoek-Brown failure criterion a modified guide for the estimation of the shaft resistance of rock-socketed drilled shafts was suggested in this paper. Through a case study it is shown that the suggested method gives a good agreement with the measured data.

수치해석을 이용한 국내 해상교량 현장타설말뚝의 강관지지효과

이주형(Lee Juhyung),신휴성(Shin Hyu-Soung),박민경(Park Minkyung),박재현(Park Jae Hyun),곽기석(Kwak Kiseok) 대한토목학회 2008 대한토목학회논문집 C Vol.28 No.3

본 연구에서는 수치해석을 통하여 국내 해상 장대교량의 기초로 사용된 대구경 현장타설말뚝의 거동특성을 분석하고 외부 강관케이싱에 의한 말뚝의 지지력 증진효과를 검증하고자 한다. 직경이 다른 3종류의 현장타설말뚝에 대하여 1) 외부강관이 없는 경우, 2) 외부강관이 있는 경우 그리고 3) 외부강관과 콘크리트가 일체화 거동을 하는 경우 등 3가지 모델을 설정하고 3차원 유한요소해석을 수행하였다. 강관과 콘크리트사이에는 경계면 요소(interface)를 적용하였으며, 지반 및 하중조건은 현장의 조건을 사용하였다. 각 모델에 대한 세부적인 변위 및 응력분석을 통하여 강관합성 현장타설말뚝의 거동특성을 파악하였다. 수치해석결과 본 해석에서 선정한 대구경 현장타설말뚝의 경우 외부강관을 구조재로 고려하는 경우 동일 하중조건에 대한 수평변위 및 수직변위가 각각 32~37%와 15~19% 정도 감소되는 것으로 나타났다. This study is concerned with the characteristics of the behavior of drilled shafts with steel casing, a material that is used for large bridge foundations in Korea, and especially for weak submerged ground conditions. The effect of steel casing on bearing capacity of drilled shafts was also verified in this study. Three large drilled shafts with 1.8, 2.4, 3.0m diameter respectively were selected, and 3-D finite element analysis has been undertaken on the following three models: 1) drilled shafts without steel casing, 2) drilled shafts with steel casing, 3) steel-concrete composite drilled shafts. Interface element between concrete core and steel casing was taken into account, and ground conditions and load combinations were applied which had been considered in the fields. Detailed characteristics of the stress and displacement distributions were evaluated to understand the characteristics of the behavior of the drilled shafts. Based on the study performed, the steel casing used as load-carrying materials in the drilled shafts can reduce the horizontal and vertical displacement of drilled shafts by 32~37% and 15~19% respectively compared with drilled shafts without steel casing.