International Science Index


11582

Strength Characteristics of Shallow Gassy Sand in the Hangzhou Bay

Abstract:In view of geological origin, formation of the shallow gas reservoir of the Hangzhou Bay, northern Zhejiang Province, eastern China, and original occurrence characteristics of the gassy sand are analyzed. Generally, gassy sand in scale gas reservoirs is in the state of residual moisture content and the approximate scope of initial matric suction of sand ranges about from 0kPa to100kPa. Results based on GDS triaxial tests show that the classical shear strength formulas of unsaturated soil can not effectively describe basic strength characteristics of gassy sand; the relationship between apparent cohesion and matric suction of gassy sand agrees well with the power function, which can reasonably be used to describe the strength of gassy sand. In the stress path of gas release, shear strength of gassy sand will increase and experimental results show the formula proposed in this paper can effectively predict the strength increment. When saturated strength indexes of the sand are used in engineering design, moderate reduction should be considered.
References:
[1] X. Q. PANG, W. Z. ZHAO, A. G. SUN, S. C. ZHANG, M. W. LI, Y. Q. DANG, F. Y. XU, R. L. ZHOU, D. W. ZHANG, Z. Y.XU, Z. Q. GUANG, J. F. CHEN, and S. M. LI, "Geochemistry and origin of the giant Quaternary shallow gas accumulations in the eastern Qaidam Basin, NW China," Organic Geochemistry, no.36, pp. 1636-1649. 2005.
[2] W. Z. LU, "Quaternary shallow gas distribution and quaternary exploration prospects in southeast coastal and Yangtze River regions of China," Nature Gas Industry, vol. 18, no. 3, pp. 25-29, 1998.
[3] W. S. JIANG, Z. YE, H. P. ZHEN, and Z. M. Yong, "Quaternary shallow gas characteristics in Hangzhou Bay and the exploration method," Nature Gas Industry, vol. 17, no. 3, pp. 20-23, 1997.
[4] D. D. RICE, and G. E. CLAYPOOL, "Generation, accumulation and resource potential of biogenic gas," Bulletin of American Association of Petroleum Geologists, no. 65, pp. 5-25, 1981.
[5] G. D.FLOODGATE, and A. G. JUDD, "The origin of shallow gas," Continental Shelf Research, vol. 12, no. 10, pp. 1145-1156, 1992.
[6] G. W. SHURR, and J. L. RIDGLEY, "Unconventional shallow biogenic gas systems," Bulletin of American Association of Petroleum Geologists, no. 86, pp. 1939-1970, 2002.
[7] R. C. SURDAM, Z. S. JIAO, and Y. GANSHIN, "A new approach to exploring for anomalously pressured gas accumulations: The key to unlocking huge, unconventional gas resources," Geological Journal of China Universities, vol. 9, no. 3, pp. 307-338, 2003.
[8] C. Y. XIE, "Effects on the hydraulic structures along the Yangtze River in Anhui province from the shallow gas in soft soil," Express Water Resources & Hydropower Information, vol. 21, no. 10, pp. 11-16, 2000.
[9] Y. Q. TANG, W. M. YE, and Y. HUANG, "Marsh gas in shallow soils and safety measures for tunnel construction," Engineering Geology, no. 67, pp. 373-378, 2003.
[10] L. W. KONG, A. G. GUO, S. Y. CHEN, and Y. Q. Huang, "Influence of shallow natural gas blowout on stratum damage and hazard analysis of pile foundation," Journal of Disaster Prevention and Mitigation Engineering, vol. 24, no. 4, pp. 375-381, 2004.
[11] M. Z. FENG, and J. JI, "The geological hazard evaluation by shallow layered natural gas in Shanghai region," Shanghai Geology, no. 4, pp. 44-47, 2006.
[12] L. W. KONG, A. G. GUO, J. B. CHEN, and G. S. LIU, "On strength property of gassy fine sand and model tests of pile foundation," Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering. Osaka, Japan: Millpress Rotterdam Netherlands, pp. 2009-2012, 2005.
[13] S. J. WHEELER, "A conceptual model for soils containing large gas bubbles," Geotechnique, no. 38, pp. 389-397, 1988.
[14] G. C. SILLS, and S. J. WHEELER, "The significance of gas for offshore operations," Geotechnique, vol. 51, no.7, pp. 629-639. 1992.
[15] G. C. SILLS, and R. GONZALEZ, "Consolidation of naturally gassy soft soil," Geotechnique, vol. 51, no. 7, pp. 629-639. 2001.
[16] VANOUDHEUSDEN, E. N. SULTAN, and P. COCHONAT, "Mechanical behavior of unsaturated marine sediments: experimental and theoretical approaches," Marine Geology, vol. 213, no. 1-4, pp. 323-342, 2004.
[17] J. L. H. GROZIC, F. NADIM, and T. J. KVALSTAD, "On the undrained shear strength of gassy clays," Computers and Geotechnics, vol. 32, no. 7, pp. 483-490, 2005,
[18] C. M. LIN, Y. L. LI, H. C. ZHOU, Z. P. ZHANG, S. W. GEORGE, and R. JENNIE, "Geology and pore-water pressure sealing of shallow biogenic gas in the Qiantang River incised valley fills," Journal of palaeogeography, vol. 11, no. 3, pp. 314-329, 2009.
[19] G. M. REN, "Discuss on pressure characteristics and the causes of the shallow biological gas reservoir in China," Petroleum Exploration and Development, vol. 26, no. 3, pp. 18-21, 1999.
[20] A. W. BISHOP, and G. E. BLIGHT, "Some aspects of effective stress in saturated and unsaturated soils," Geotechnique, vol. 13, no. 3, pp. 177-197, 1963.
[21] D. G. FREDLUND and MORGENSTERN, "The shear strength of unsaturated soils," Canadian Geotechnical Journal, vol. 15, no. 3, pp. 313-321, 1978.
[22] S. K. VANAPALLI, D. G. FREDLUND, D. E. PAUFAHL, and A. W. CLIFTON, "Model for predication of shear with respect to matric suction," Canadian Geotechnical Journal, no. 33, pp. 379-392, 1996.