Effects of increase in pore water pressure on dynamic parameters of hyperbolic model
SUN Rui1 LI Xiaofei2 CHEN Longwei1 YUAN Xiaoming1 LI Bo2
1. Key Lab of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin 150080, China;
2. Binzhou College, Binzhou 256600, China
The key for using a hyperbolic model to describe stress-strain relationship of liquefiable soil is to determine its cyclic maximum shear modulus and its cyclic ultimate shear stress under cyclic loading. Aiming at several kinds of sand soil with different relative densities, liquefaction tests under the action of cyclic stresses of different equal-amplitudes were uniformly consolidated using a new high-precision dynamic tri-axial apparatus to study effects’ mode and law of pore-water pressure on maximum shear modulus and ultimate shear stress of saturated sand soil. Formulas to calculate cyclic maximum shear modulus and ultimate shear stress of sand soil with different precisions were proposed considering increase in pore-water pressure. The results showed that effects of increase in pore-water pressure on cyclic maximum shear modulus and ultimate shear stress of sand soil are obvious, sand soil’s cyclic maximum shear modulus and ultimate shear stress decrease with increase in pore-water pressure; the relation between saturated sans soil’s maximum shear modulus and pore water pressure ratio can be expressed as a unified linear relation expression to be independent upon sand soil types and their relative densities, pore water pressure ratio is equal to the relative reduction of cyclic maximum shear modulus; the relation between cyclic ultimate shear stress of saturated sand soil and pore water pressure ratio can accurately be expressed as a quadratic curve relation to be dependent on sand soil types and their relative densities, it also can be expressed as a unified linear relation expression to be independent upon sand soil types and their relative densities considering simplification, pore water pressure ratio is equal to the relative reduction of cyclic ultimate shear stress; Hardin initial maximum shear modulus calculation formula is not suitable for calculation of cyclic maximum shear modulus considering increase in pore water pressure, Hardin formula generally overestimates sand soil’s cyclic maximum shear modulus in liquefaction process; especially, the cyclic maximum shear modulus can be overestimated almost 80%-140% within the sensitive interval of pore water pressure ratio of 0.6 ~0.8.
孙锐1，李晓飞2，陈龙伟1，袁晓铭1, 李 波2. 孔压增长下双曲线模型参数研究[J]. 振动与冲击, 2018, 37(7): 1-7.
SUN Rui1 LI Xiaofei2 CHEN Longwei1 YUAN Xiaoming1 LI Bo2. Effects of increase in pore water pressure on dynamic parameters of hyperbolic model. JOURNAL OF VIBRATION AND SHOCK, 2018, 37(7): 1-7.
[1] 陈龙伟, 袁晓铭, 孙锐. 2011年新西兰Mw6.3地震液化及岩土震害评述[J]. 世界地震工程, 2013, 29(3): 1-9. (CHEN Long-wei, YUAN Xiao-ming, SUN Rui. Review of liquefac-tion phenomena and geotechnical damage in the 2011 New Zealand Mw6.3 earthquake[J]. World Earthquake Engineering, 2013, 29(3): 1-9. (In Chinese))
[2] 张建民, 邵生俊. 往返荷载下饱和砂土瞬态有效抗剪强度的研究[J]. 水利学报, 1987, (10): 33-40. (ZHANG Jian-min, SHAO Sheng-jun. Study on transient effective shear-strength of saturated sand under cyclic loading[J]. Journal of Hydraulic Engineering, 1987, (10): 33-40. (In Chinese) )
[3] R. L. Kondner. Hyperbolic stress strain response: cohesive soils[J]. Journal of the Soil Mechanics & Foundations Divi-sion, ASCE, 1963, 89(1):115-143.
[4] Hardin, B. O, Drnevich, V. P. Shear Modulus and Damping in Soils[J]. Journal of Geotechnical Engineering Division, ASCE, 1972, 98( 6):603-624.
[5] 丰万玲，石兆吉. 判别水平土层液化势的孔隙水压力分析方法[J]. 工程抗震, 1988,(4): 30-33. (FENG Wanling, SHI Zhaoji. Method of pore water pressure analysis for discrimi-nation of liquefaction potential of horizontal layer[J]. Earth-quake Resistant Engineering, 1988, (4): 30-33. ( In Chinese) )
[6] 姬美秀，陈云敏. 不排水循环荷载作用过程中累积孔压对细砂弹性剪切模量Gmax 的影响[J]. 岩土力学, 2005,26(6):884-888.(JI Meixiu, CHEN Yunming. Effect of accumulated pore pressure on shear modulus Gmax of saturated fine sand during undrained cyclic loading[J]. Rock and Soil Mechanics, 2005,26(6):884-888.( In Chinese))
[7] N. Matasovic, M. Vucetic. Cyclic characterization of liquefi-able sands[J]. Journal of Geotechnical Engineering. 1992,119(11): 1805-1822.
[8] R. Dobry, R. Ladd, F Yokel, et al. Prediction of pore water pressure buildup and liquefaction of sands during earthquakes by the cyclic strain method [S]. National Bureau of Standards Building Science Series 138. 1982.
[9] 李文泱，刘惠珊. 孔隙水压力对饱和砂的剪切模量和阻尼比的影响[J]. 岩土工程学报, 1983,5(4): 56-67.(LI Wenyang, LIU Huishan. Influence of pore water pressure on shear modulus and damping ratio of saturated sands[J]. Chinese Journal of Geotechnical Engineering, 1983,5(4): 56-67 ( In Chinese) )
[10] 中华人民共和国水利部. GB/SL237-1999 土工实验规程[S]. 北京：中华水利水电出版社,1999.
