|
|
|
| A NEW METHOD FOR TORQUE FACTOR CALIBRATION OF COMBINED TORSIONAL SHEAR RESONANT COLUMN APPARATUS |
| BAI Lidong1，2，XIANG Wei2 |
(1. Faculty of Engineering，China University of Geosciences，Wuhan，Hubei 430074，China；
2. Guizhou Expressway Development Corporation，Guiyang，Guizhou 550004，China) |
|
|
|
|
Abstract Effects of torsional shear frequency，input voltage and specimen torsional stiffness on the torque factor are systematically investigated on the basis of a number of torsional shear tests on six aluminum calibration bars using the combined torsional shear resonant column apparatus. Results indicate that the torque factor of this type of device slightly decreases with increasing torsional shear frequency and input voltage，but significantly increases with increasing torsional stiffness of specimen，due to the inherent design limitation of the electromagnetic drive system. When the constant torque factor obtained from the traditional calibration method，which is suggested by the manufacturer，is employed to analyze the shear modulus of calibration bar，testing result is significantly underestimated with the error of 14% for the greatest stiffness calibration bar(Bar #6)，and overestimated with the error of 25% for the smallest stiffness bar(Bar #1). Therefore，a new calibration procedure is proposed to overcome the error induced by the inherent design weakness of the drive system. It can minimize the testing error within 3% for torsional shear tests conducted by this type of resonant column device.
|
|
Received: 08 April 2011
|
|
|
|
| [1] IWASAKI T，TATSUOKA F，TAKAGI Y. Shear modulus of sands under cyclic torsional shear loading[J]. Soils and Foundations，1978，18(1)：39–56.
[2] NI S H. Dynamic properties of sand under true triaxial stress states from resonant column/torsional shear tests[Ph. D. Thesis][D]. Austin，USA：The University of Texas at Austin，1987.
[3] HONGNAM N，KOSEKI J，SATO T. Effect of specimen size on quasi-elastic properties of Toyoura sand in hollow cylinder triaxial and torsional shear tests[J]. Geotechnical Testing Journal，ASTM，2008，31(2)：132–141.
[4] SASANAKUL I，BAY J A. Calibration of equipment damping in a resonant column and torsional shear testing device[J]. Geotechnical Testing Journal，2010，33(5)：363–374.
[5] 牛建新，汪闻绍. 循环扭剪试验中饱和砂土的某些动力特性[J]. 水利学报，1994，25(5)：77–83.(NIU Jianxin，WANG Wenshao. Some dynamic properties of saturated sands with torsional shear apparatus[J]. Journal of Hydraulic Engineering，1994，25(5)：78–83.(in Chinese))
[6] 刘汉龙，陈育民. 动扭剪试验中砂土液化后流动特性分析[J]. 岩土力学，2009，30(6)：1 537–1 541.(LIU Hanlong，CHEN Yumin. Analysis of flow characteristics of dynamic torsional tests on post liquefied sand[J]. Rock and Soil Mechanics，2009，30(6)：1 537–1 541. (in Chinese))
[7] 李 驰，王建华. 饱和软黏土动力学特性循环扭剪试验研究[J]. 岩土力学，2008，29(2)：460–464.(LI Chi，WANG Jianhua. Cyclic torsional shear experimental studies on dynamic characters for saturated soft clay[J]. Rock and Soil Mechanics，2008，29(2)：460–464.(in Chinese))
[8] 李 振，骆亚生，邢义川. 动扭剪荷载作用下粉煤灰动力特性试验研究[J]. 岩石力学与工程学报，2006，25(增1)：3 080–3 086.(LI Zhen，LUO Yasheng，XING Yichuan. Cyclic torsional shear experimental studies on dynamic characters for saturated soft clay[J]. Chinese Journal of Rock Mechanics and Engineering，2006，25(Supp.1)：3 080–3 086.(in Chinese))
[9] 田堪良，张慧莉，张伯平，等. 动扭剪荷载作用下非饱和黄土动力特性试验研究[J]. 岩石力学与工程学报，2004，23(24)：4 151–4 156. (TIAN Kanliang，ZHANG Huili，ZHANG Boping，et al. Cyclic torsional shear experimental studies on dynamic characters for saturated soft clay[J]. Chinese Journal of Rock Mechanics and Engineering，2004，23(24)：4 151–4 156.(in Chinese))
[10] American Society of Testing Materials. D4015¬—92 Standard test methods for modulus and damping of soils by the resonant-column method[S]. Philadelphia：American Society for Testing and Materials，2000.
[11] HARDIN B O，DRNEVICH V P. Shear modulus and damping in soils：measurement and parameter effects[J]. Journal of the Soil Mechanics and Foundations Division，ASCE，1972，98(6)：603–624.
[12] DRNEVICH V P，RICHART F E. Dynamic prestraining of dry sand[J]. Journal of the Soil Mechanics and Foundations Division，ASCE，1970，96(2)：453–469.
[13] LI X S，YANG W L. Effects of vibration history on modulus and damping of dry sand[J]. Journal of Geotechnical and Geoenvironmental Engineering，ASCE，1998，124(11)：1 071–1 081.
[14] BAI L D. Preloading effects on dynamic sand behavior by resonant column tests[Ph. D. Thesis][D]. Berlin：School of Planning Building Environment，Technical University of Berlin，2011.
[15] KIM D S，STOKOE K H. Torsional motion monitoring-system for small-strain(10(－5) to 10(－3) percent) soil testing[J]. Geotechnical Testing Journal，1994，17(1)：17–26.
[16] YOUN J U，CHOO Y W，KIM D S. Measurement of small-strain shear modulus Gmax of dry and saturated sands by bender element，resonant column，and torsional shear tests[J]. Canadian Geotechnical Journal，2008，45(10)：1 426–1 438.
[17] Geotechnical Digital Systems Instruments Company(GDS). The GDS resonant column system handbook[R]. London：Geotechnical Digital Systems Instruments Company(GDS)，2008.
[18] HIGDON A，OHLSEN E H，STILES W B，et al. Mechanics of materials[M]. ISE editions. Singapore：John Wiley and Sons Inc.，1985.
[19] SHIGLEY J E，MISHCKE C R. Mechanical engineering design[M]. ISE ed. New York：McGraw-Hill Education，1990：123–128. |
|
|
|
2012, Vol. 31 
