海洋黏土孔压增长和刚度弱化的循环阈值剪应变试验研究

肖兴; 吉东伟; 杭天柱; 吴琪; 陈国兴

doi:10.11779/CJGE2023S10005

海洋黏土孔压增长和刚度弱化的循环阈值剪应变试验研究 English Version

肖兴^1,,
吉东伟¹,
杭天柱¹,
吴琪^{1, 2, ,},
陈国兴^{1, 2}

1.
南京工业大学岩土工程研究所, 江苏南京 210009
2.
江苏省土木工程防震技术研究中心, 江苏南京 210009

基金项目:

国家自然科学基金项目 51978334

详细信息

作者简介:
作者简介：肖兴(1995—)，男，博士研究生，主要从事海洋土动力特性试验研究。E-mail: xx_0524@126.com

通讯作者:
吴琪, E-mail：qw09061801@163.com

中图分类号: TU447
计量
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出版历程
- 收稿日期: 2023-07-05
- 网络出版日期: 2023-11-23
- 刊出日期: 2023-10-31

Cyclic threshold shear strains for pore water pressure generation and stiffness degradation in marine clay

XIAO Xing^1,,
JI Dongwei¹,
HANG Tianzhu¹,
WU Qi^{1, 2, ,},
CHEN Guoxing^{1, 2}

1.
Institute of Geotechnical Engineering, Nanjing Tech University, Nanjing 210009, China
2.
Civil Engineering and Earthquake Disaster Prevention Center of Jiangsu Province, Nanjing 210009, China

摘要

摘要: 循环阈值剪应变是循环荷载作用下饱和土体的基本特性。针对不同塑性指数（I_p）的长江口原状饱和海洋黏土，开展了一系列应变控制逐级加载的不排水循环三轴试验，研究了引起原状饱和海洋黏土孔压增长的循环阈值剪应变（γ_tp）和刚度弱化的循环阈值剪应变（γ_td）。结果表明：长江口海洋黏土γ_tp和γ_td均随I_p的增大而增大，相同测试条件下，同一海洋黏土的γ_tp大于γ_td，I_p ≈ 17时，γ_tp = 0.018%~0.019%，γ_td = 0.011%~0.012%，I_p ≈ 30时，γ_tp =0.037%~0.041%，γ_td = 0.022%~0.027%；长江口海洋黏土刚度弱化的发生不一定需要孔压的增长，但会因孔压增长而加剧。与已有文献中陆域黏土的γ_tp和γ_td的对比分析发现：特殊的海洋沉积环境是造成长江口海洋黏土γ_tp和γ_td低于原状陆域黏土的原因。
- 海洋黏土 /
- 孔压增长 /
- 刚度弱化 /
- 循环阈值剪应变 /
- 循环三轴试验
Abstract: The cyclic threshold shear strain is a fundamental property of saturated soils under cyclic loading. To investigate the cyclic threshold shear strains for pore water pressure generation (γ_tp) and stiffness degradation (γ_td), a series of strain-controlled multistage undrained cyclic triaxial tests are carried out on the in-situ saturated marine clay in the Yangtze River estuary with different values of plasticity index I_p. The test results show that both γ_tp and γ_td increase with the increasing I_p of the marine clay, and γ_tp is greater than γ_td for the same marine clay tested under the same conditions, with γ_tp = 0.018% ~ 0.019%, γ_td = 0.011% ~ 0.012% for I_p of 17, and γ_tp = 0.037% ~ 0.041%, γ_td = 0.022% ~ 0.027% for I_p of 30. Moreover, the development of stiffness degradation may not necessarily require the pore water pressure generation, but can be aggravated by it. The γ_tp and γ_td of the marine clay are compared with those of the terrestrial soils cited from the published literatures, indicating that the special marine sedimentary environment causes the γ_tp and γ_td of the marine clay in the Yangtze estuary to be smaller than those of the undisturbed terrestrial clay.
- marine clay /
- pore water pressure generation /
- stiffness degradation /
- cyclic threshold shear strain /
- cyclic triaxial test

HTML全文

图 1 J7-10应变、应力、动剪切模量和孔压随循环振次的变化

Figure 1. Variation of strain, stress, dynamic shear modulus and pore pressure with cycles for J7-10

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代表性试样J7-8和J7-10的 $r{_{{{\text{u}}}i, N}{}^{\ast }}$ 与 ${\gamma _{{\text{c}}}}$ 的关系曲线

Relation curves between $r{_{{{\text{u}}}i, N}{}^{\ast } }$ and ${\gamma _{{\text{c}}}}$ for J7-8 and J7-10

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图 3 代表性试样J7-8和J7-10的δ与N的关系曲线

Figure 3. Relation curves between δ and N for J7-8 and J7-10

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图 4 代表性试样J7-8和J7-10的t与γ_c的关系曲线

Figure 4. Relation curves between t and γ_c for J7-8 and J7-10

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图 5 长江口海洋黏土与陆域黏土γ_tp和γ_td差异对比^{[4, 9, 11, 12, 20-21]}

Figure 5. Comparison of γ_tp and γ_td between marine clay in Yangtze River estuary and terrestrial clay^{[4, 9, 11, 12, 20-21]}

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表 1 海洋黏土基本物理指标及试验工况

Table 1 Basic physical properties and experimental conditions of marine clay

试样编号	基本物理指标						试验条件
试样编号	海床以下深度/m	G_s	含水率/ %	天然密度/ (g·cm^-3)	塑性指数 I_p	土类名称	初始有效固结压力 ${\sigma '_{{{\text{c}}}0}}$ /kPa	γ_c/ %	固结后体变/%
J7-4	7.6~7.8	2.66	42.22	1.78	30.6	黏土	55	0.015, 0.03, 0.075, 0.15, 0.75, 1, 3	3.81
J7-6	9.6~9.8	2.64	47.23	1.75	32.8	黏土	70		4.64
J7-8	11.6~11.8	2.55	45.61	1.59	17.4	黏土	80		5.31
J7-10	14.6~14.8	2.65	43.64	1.77	34.5	黏土	100		3.43
J7-14	18.6~18.8	2.63	42.21	1.74	31.9	黏土	130		4.94
J7-24	28.6~28.8	2.65	35.35	1.93	17.2	黏土	200		5.56

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表 2 海洋黏土γ_tp和γ_td汇总表

Table 2 Summary table of γ_tp and γ_td of marine clay

试样编号	塑性指数I_p	γ_tp /%	γ_td /%	γ_tp/γ_td
J7-8	17.4	0.018	0.011	1.64
J7-24	17.2	0.019	0.012	1.58
J7-10	34.5	0.040	0.027	1.48
J7-6	32.8	0.039	0.026	1.50
J7-14	31.9	0.037	0.023	1.61
J7-4	30.6	0.041	0.022	1.86

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