Undrained shear strength evaluation for hydrate-bearing sediment overlying strata in the Shenhu area, northern South China Sea
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摘要
The undrained shear strength of shallow strata is a critical parameter for safety design in deep-water operations.In situ piezocone penetration tests(CPTU) and laboratory experiments are performed at Site W18-19 in the Shenhu area, northern South China Sea, where China's first marine hydrate exploitation operation is due to be located. The validation of the undrained shear strength prediction model based on CPTU parameters. Different laboratory tests, including pocket penetrometer, torvane, miniature vane and unconsolidated undrained triaxial tests, are employed to solve empirical cone coefficients by statistical and mathematical methods. Finally, an optimized model is proposed to describe the longitudinal distribution of undrained shear strength in calcareous clay strata in the Shenhu area. Research results reveal that average empirical cone coefficients based on total cone resistance, effective resistance, and excess-pore pressure are 13.8, 4.2 and 14.4, respectively. The undrained shear strength prediction model shows a good fit with the laboratory results only within specific intervals based on their compaction degree and gas-bearing conditions. The optimized prediction model in piecewise function format can be used to describe the longitudinal distribution of the undrained shear strength for calcareous clay within all depth intervals from the mud-line to the upper boundary of hydrate-bearing sediments(HBS). The optimized prediction result indicates that the effective cone resistance model is suitable for very soft to firm calcareous clays,the excess-pore pressure model can depict the undrained shear strength for firm to very stiff but gas-free clays,while the total cone resistance model is advantageous for evaluating the undrained shear strength for very stiff and gassy clays. The optimized model in piecewise function format can considerably improve the adaptability of empirical models for calcareous clay in the Shenhu area. These results are significant for safety evaluations of proposed hydrate exploitation projects.
The undrained shear strength of shallow strata is a critical parameter for safety design in deep-water operations.In situ piezocone penetration tests(CPTU) and laboratory experiments are performed at Site W18-19 in the Shenhu area, northern South China Sea, where China's first marine hydrate exploitation operation is due to be located. The validation of the undrained shear strength prediction model based on CPTU parameters. Different laboratory tests, including pocket penetrometer, torvane, miniature vane and unconsolidated undrained triaxial tests, are employed to solve empirical cone coefficients by statistical and mathematical methods. Finally, an optimized model is proposed to describe the longitudinal distribution of undrained shear strength in calcareous clay strata in the Shenhu area. Research results reveal that average empirical cone coefficients based on total cone resistance, effective resistance, and excess-pore pressure are 13.8, 4.2 and 14.4, respectively. The undrained shear strength prediction model shows a good fit with the laboratory results only within specific intervals based on their compaction degree and gas-bearing conditions. The optimized prediction model in piecewise function format can be used to describe the longitudinal distribution of the undrained shear strength for calcareous clay within all depth intervals from the mud-line to the upper boundary of hydrate-bearing sediments(HBS). The optimized prediction result indicates that the effective cone resistance model is suitable for very soft to firm calcareous clays,the excess-pore pressure model can depict the undrained shear strength for firm to very stiff but gas-free clays,while the total cone resistance model is advantageous for evaluating the undrained shear strength for very stiff and gassy clays. The optimized model in piecewise function format can considerably improve the adaptability of empirical models for calcareous clay in the Shenhu area. These results are significant for safety evaluations of proposed hydrate exploitation projects.
The undrained shear strength of shallow strata is a critical parameter for safety design in deep-water operations.In situ piezocone penetration tests(CPTU) and laboratory experiments are performed at Site W18-19 in the Shenhu area, northern South China Sea, where China's first marine hydrate exploitation operation is due to be located. The validation of the undrained shear strength prediction model based on CPTU parameters. Different laboratory tests, including pocket penetrometer, torvane, miniature vane and unconsolidated undrained triaxial tests, are employed to solve empirical cone coefficients by statistical and mathematical methods. Finally, an optimized model is proposed to describe the longitudinal distribution of undrained shear strength in calcareous clay strata in the Shenhu area. Research results reveal that average empirical cone coefficients based on total cone resistance, effective resistance, and excess-pore pressure are 13.8, 4.2 and 14.4, respectively. The undrained shear strength prediction model shows a good fit with the laboratory results only within specific intervals based on their compaction degree and gas-bearing conditions. The optimized prediction model in piecewise function format can be used to describe the longitudinal distribution of the undrained shear strength for calcareous clay within all depth intervals from the mud-line to the upper boundary of hydrate-bearing sediments(HBS). The optimized prediction result indicates that the effective cone resistance model is suitable for very soft to firm calcareous clays,the excess-pore pressure model can depict the undrained shear strength for firm to very stiff but gas-free clays,while the total cone resistance model is advantageous for evaluating the undrained shear strength for very stiff and gassy clays. The optimized model in piecewise function format can considerably improve the adaptability of empirical models for calcareous clay in the Shenhu area. These results are significant for safety evaluations of proposed hydrate exploitation projects.
引文
Aas G,Lacasse S,Lunne T,et al.1986.Use of In Situ Tests in Geotechnical Engineering.American Society of Civil Engineers,New York,NY:1-15
An Yanyong,Guo Yanmo,Li Xiangfeng.2009.Analysis of pore pressure static cone penetration test to determine soft clay strength.Site Investigation Science and Technology(in Chinese),(3):8-12
Cai Guojun,Lin Jun,Liu Songyu,et al.2017.Characterization of spatial variability of CPTU data in a liquefaction site improved by vibro-compaction method.KSCE Journal of Civil Engineering,21(1):209-219,doi:10.1007/s12205-016-0631-1
Cai Guojun,Liu Songyu,Puppala A J.2016.Evaluation of geotechnical parameters of a lagoonal clay deposit in Jiangsu Lixia River area of China by seismic piezocone tests.KSCE Journal of Civil Engineering,20(5):1769-1782,doi:10.1007/s12205-015-0164-z
Ching J,Phoon K K.2012.Modeling parameters of structured clays as a multivariate normal distribution.Canadian Geotechnical Journal,49(5):522-545,doi:10.1139/t2012-015
Chung S F,Randolph M F,Schneider J A.2006.Effect of penetration rate on penetrometer resistance in clay.Journal of Geotechnical and Geoenvironmental Engineering,132(9):1188-1196,doi:10.1061/(ASCE)1090-0241(2006)132:9(1188)
Ebrahimian B,Movahed V,Pasha A Y.2012.Evaluation of undrained shear strength of marine clay using cone penetration resistance at South Pars field in Iran.Ocean Engineering,54:182-195,doi:10.1016/j.oceaneng.2012.07.018
Han Hongwei,Li Zhijun,Huang Wenfeng,et al.2015.The uniaxial compressive strength of the arctic summer sea ice.Acta Oceanologica Sinica,34(1):129-136,doi:10.1007/s13131-015-0598-7
Hu Gaowei,Li Yanlong,Wu Nengyou,et al.2017.Undrained shear strength estimation of the cover layer of hydrate at Site W18/19of Shenhu area.Marine Geology&Quaternary Geology(in Chinese),37(5):151-158
Ji Fudong,Jia Yonggang,Liu Xiaolei,et al.2016.In situ measurement of the engineering mechanical properties of seafloor sediment.Marine Geology&Quaternary Geology(in Chinese),36(3):191-200
Konrad J M,Law K T.2015.Preconsolidation pressure from piezocone tests in marine clays.Géotechnique,37(2):177-190
Kvenvolden K A.1998.A primer on the geological occurrence of gas hydrate.Geological Society London Special Publications,137(1):9-30,doi:10.1144/GSL.SP.1998.137.01.02
La R,Zebdi M,Leroueil S,et al.1990.Piezocone tests in sensitive clays of eastern Canada.International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,27(6):353-356
Li Yanlong,Liu Changling,Liu Lele.2016a.Damage statistic constitutive model of hydrate-bearing sediments and the determination method of parameters.Acta Petrolei Sinica(in Chinese),37(10):1273-1279
Li Yanlong,Liu Changling,Liu Lele,et al.2016b.Key issues for triaxial test of hydrate-bearing sediment.Advances in New and Renewable Energy(in Chinese),4(4):279-285
Li Xuepeng,Yang Xiaojuan,Cai Guojun,et al.2016.Determination of undrained shear strength of clayey soil in Ningbo based on CPTU.Journal of Chongqing Jiaotong University(in Chinese),35(6):20-23,50
Liu Changling,Meng Qingguo,Hu Gaowei,et al.2017.Characterization of hydrate-bearing sediments recovered from the Shenhu area of the South China Sea.Interpretation,5(3):SM13-SM23,doi:10.1190/INT-2016-0211.1
Liu Weizheng,Shi Minglei,Xu Linrong.2013.Elastoplastic analysis of cylindrical cavity expansion in natural sedimentary soft clay with structure damage.Chinese Journal of Geotechnical Engineering(in Chinese),35(3):487-494
Low H E,Randolph M F.2010.Strength measurement for nearseabed surface soft soil using manually operated miniature fullflow penetrometer.Journal of Geotechnical and Geoenvironmental Engineering,136(11):1565-1573,doi:10.1061/(ASCE)GT.1943-5606.0000379
Lunne T,Christoffersen H,Tjelta,et al.1987.Engineering use of piezocone data in North Sea clays.International Journal of Rock Mechanics&Mining Sciences&Geo-mechanics Abstracts,24:92
Ma Haopeng,Chen Zuyu,Yu Shu.2014.Correlations of soil shear strength with specific penetration resistance of CPT in Shanghai area.Rock and Soil Mechanics(in Chinese),35(2):536-542
M?ynarek Z,Gogolik S,Pó?torak J.2012.The effect of varied stiffness of soil layers on interpretation of CPTU penetration characteristics.Archives of Civil and Mechanical Engineering,12(2):253-264,doi:10.1016/j.acme.2012.03.013
Senneset K,Janbu N,Svano G.1982.Strength and deformation parameters for CPT.In:Proceedings of the 2nd European Symposium on Penetration Testing.Amsterdam,The Netherlands
Shin Y J,Kim D.2011.Assessment of undrained shear strength based on cone penetration test(CPT)for clayey soils.KSCE Journal of Civil Engineering,15(7):1161-1166,doi:10.1007/s12205-011-0808-6
Sultan N,Savoye B,Jouet G,et al.2010.Investigation of a possible submarine landslide at the Var delta front(Nice continental slope,southeast France).Canadian Geotechnical Journal,47(4):486-496,doi:10.1139/T09-105
Tong Liyuan,Wang Qiang,Du Guangyin,et al.2011.Determination of undrained shear strength using piezocone penetration test in clayey soil for bridge foundation.Journal of Southeast University,27(2):201-205
Wang Yanmin,Liu Shaowen,Hao Feifei,et al.2017.Geothermal investigation of the thickness of gas hydrate stability zone in the north continental margin of the South China Sea.Acta Oceanologica Sinica,36(4):72-79,doi:10.1007/s13131-017-1014-2
Wei L,Pant R,Tumay M T.2010.Evaluation of undrained shear strength of soft New Orleans clay using piezocone.In:Proceedings of the 2nd International Symposium on Cone Penetration Testing.Huntington Beach,CA
Wu Nengyou,Yang Shengxiong,Zhang Haiqi,et al.2010.Gas hydrate system of Shenhu Area,northern South China Sea:wireline logging,geochemical results and preliminary resources estimates.In:Offshore Technology Conference.Houston,Texas,USA
Wu Nengyou,Zhang Haiqi,Yang Shengxiong,et al.2011.Gas hydrate system of Shenhu area,northern South China Sea:Geochemical Results.Journal of Geological Research,2011:370298
Yang Yijun,Tong Liyuan,Zhu Ning,et al.2016.Evaluation and application of undrained shear strength in excavation from piezocone tests(CPTU).Chinese Journal of Underground Space and Engineering(in Chinese),12(4):1095-1101
Yang Shengxiong,Zhang Ming,Liang Jinqiang,et al.2015.Preliminary results of China’s third gas hydrate drilling expedition:a critical step from discovery to development in the South China Sea.Fire in the Ice,15(2):1-5
An Yanyong,Guo Yanmo,Li Xiangfeng.2009.Analysis of pore pressure static cone penetration test to determine soft clay strength.Site Investigation Science and Technology(in Chinese),(3):8-12
Cai Guojun,Lin Jun,Liu Songyu,et al.2017.Characterization of spatial variability of CPTU data in a liquefaction site improved by vibro-compaction method.KSCE Journal of Civil Engineering,21(1):209-219,doi:10.1007/s12205-016-0631-1
Cai Guojun,Liu Songyu,Puppala A J.2016.Evaluation of geotechnical parameters of a lagoonal clay deposit in Jiangsu Lixia River area of China by seismic piezocone tests.KSCE Journal of Civil Engineering,20(5):1769-1782,doi:10.1007/s12205-015-0164-z
Ching J,Phoon K K.2012.Modeling parameters of structured clays as a multivariate normal distribution.Canadian Geotechnical Journal,49(5):522-545,doi:10.1139/t2012-015
Chung S F,Randolph M F,Schneider J A.2006.Effect of penetration rate on penetrometer resistance in clay.Journal of Geotechnical and Geoenvironmental Engineering,132(9):1188-1196,doi:10.1061/(ASCE)1090-0241(2006)132:9(1188)
Ebrahimian B,Movahed V,Pasha A Y.2012.Evaluation of undrained shear strength of marine clay using cone penetration resistance at South Pars field in Iran.Ocean Engineering,54:182-195,doi:10.1016/j.oceaneng.2012.07.018
Han Hongwei,Li Zhijun,Huang Wenfeng,et al.2015.The uniaxial compressive strength of the arctic summer sea ice.Acta Oceanologica Sinica,34(1):129-136,doi:10.1007/s13131-015-0598-7
Hu Gaowei,Li Yanlong,Wu Nengyou,et al.2017.Undrained shear strength estimation of the cover layer of hydrate at Site W18/19of Shenhu area.Marine Geology&Quaternary Geology(in Chinese),37(5):151-158
Ji Fudong,Jia Yonggang,Liu Xiaolei,et al.2016.In situ measurement of the engineering mechanical properties of seafloor sediment.Marine Geology&Quaternary Geology(in Chinese),36(3):191-200
Konrad J M,Law K T.2015.Preconsolidation pressure from piezocone tests in marine clays.Géotechnique,37(2):177-190
Kvenvolden K A.1998.A primer on the geological occurrence of gas hydrate.Geological Society London Special Publications,137(1):9-30,doi:10.1144/GSL.SP.1998.137.01.02
La R,Zebdi M,Leroueil S,et al.1990.Piezocone tests in sensitive clays of eastern Canada.International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,27(6):353-356
Li Yanlong,Liu Changling,Liu Lele.2016a.Damage statistic constitutive model of hydrate-bearing sediments and the determination method of parameters.Acta Petrolei Sinica(in Chinese),37(10):1273-1279
Li Yanlong,Liu Changling,Liu Lele,et al.2016b.Key issues for triaxial test of hydrate-bearing sediment.Advances in New and Renewable Energy(in Chinese),4(4):279-285
Li Xuepeng,Yang Xiaojuan,Cai Guojun,et al.2016.Determination of undrained shear strength of clayey soil in Ningbo based on CPTU.Journal of Chongqing Jiaotong University(in Chinese),35(6):20-23,50
Liu Changling,Meng Qingguo,Hu Gaowei,et al.2017.Characterization of hydrate-bearing sediments recovered from the Shenhu area of the South China Sea.Interpretation,5(3):SM13-SM23,doi:10.1190/INT-2016-0211.1
Liu Weizheng,Shi Minglei,Xu Linrong.2013.Elastoplastic analysis of cylindrical cavity expansion in natural sedimentary soft clay with structure damage.Chinese Journal of Geotechnical Engineering(in Chinese),35(3):487-494
Low H E,Randolph M F.2010.Strength measurement for nearseabed surface soft soil using manually operated miniature fullflow penetrometer.Journal of Geotechnical and Geoenvironmental Engineering,136(11):1565-1573,doi:10.1061/(ASCE)GT.1943-5606.0000379
Lunne T,Christoffersen H,Tjelta,et al.1987.Engineering use of piezocone data in North Sea clays.International Journal of Rock Mechanics&Mining Sciences&Geo-mechanics Abstracts,24:92
Ma Haopeng,Chen Zuyu,Yu Shu.2014.Correlations of soil shear strength with specific penetration resistance of CPT in Shanghai area.Rock and Soil Mechanics(in Chinese),35(2):536-542
M?ynarek Z,Gogolik S,Pó?torak J.2012.The effect of varied stiffness of soil layers on interpretation of CPTU penetration characteristics.Archives of Civil and Mechanical Engineering,12(2):253-264,doi:10.1016/j.acme.2012.03.013
Senneset K,Janbu N,Svano G.1982.Strength and deformation parameters for CPT.In:Proceedings of the 2nd European Symposium on Penetration Testing.Amsterdam,The Netherlands
Shin Y J,Kim D.2011.Assessment of undrained shear strength based on cone penetration test(CPT)for clayey soils.KSCE Journal of Civil Engineering,15(7):1161-1166,doi:10.1007/s12205-011-0808-6
Sultan N,Savoye B,Jouet G,et al.2010.Investigation of a possible submarine landslide at the Var delta front(Nice continental slope,southeast France).Canadian Geotechnical Journal,47(4):486-496,doi:10.1139/T09-105
Tong Liyuan,Wang Qiang,Du Guangyin,et al.2011.Determination of undrained shear strength using piezocone penetration test in clayey soil for bridge foundation.Journal of Southeast University,27(2):201-205
Wang Yanmin,Liu Shaowen,Hao Feifei,et al.2017.Geothermal investigation of the thickness of gas hydrate stability zone in the north continental margin of the South China Sea.Acta Oceanologica Sinica,36(4):72-79,doi:10.1007/s13131-017-1014-2
Wei L,Pant R,Tumay M T.2010.Evaluation of undrained shear strength of soft New Orleans clay using piezocone.In:Proceedings of the 2nd International Symposium on Cone Penetration Testing.Huntington Beach,CA
Wu Nengyou,Yang Shengxiong,Zhang Haiqi,et al.2010.Gas hydrate system of Shenhu Area,northern South China Sea:wireline logging,geochemical results and preliminary resources estimates.In:Offshore Technology Conference.Houston,Texas,USA
Wu Nengyou,Zhang Haiqi,Yang Shengxiong,et al.2011.Gas hydrate system of Shenhu area,northern South China Sea:Geochemical Results.Journal of Geological Research,2011:370298
Yang Yijun,Tong Liyuan,Zhu Ning,et al.2016.Evaluation and application of undrained shear strength in excavation from piezocone tests(CPTU).Chinese Journal of Underground Space and Engineering(in Chinese),12(4):1095-1101
Yang Shengxiong,Zhang Ming,Liang Jinqiang,et al.2015.Preliminary results of China’s third gas hydrate drilling expedition:a critical step from discovery to development in the South China Sea.Fire in the Ice,15(2):1-5