Discrete element numerical simulation of the accumulation process of wave-induced pore water pressure in the seabed
-
摘要: 海床土层在波浪的循环荷载作用下会逐渐累积孔压，降低土层的稳定性，并威胁海上工程。为了研究孔隙水压力的累积机制，本文提出离散元孔隙密度流方法，并改进研发离散元分析软件MatDEM，实现了海床沉积物孔压的累积过程模拟。基于现场试验装置及土体力学参数建立离散元模型，通过对比试验和数值模拟结果发现：对海床沉积物施加波浪荷载后，表层土体中产生较高孔压，并逐渐向深层传递；在循环波浪荷载作用下，土颗粒间孔压累积范围逐渐增加；当孔压累积时间足够长时，土层中孔压收敛于所施加最大荷载与最小荷载的平均值，此时若孔压达到初始有效应力，土体将发生液化，内部土颗粒成为再悬浮沉积物；在周期性波浪荷载作用下，土颗粒液化悬浮后发生移动，浅层颗粒位移量大，土体整体表现为圆弧形移动。Abstract: The seabed soil layer will gradually accumulate pore pressure under the action of wave cyclic load, reduce the stability of the soil layer, and threaten offshore engineering. In order to study the accumulation mechanism of pore water pressure, the discrete element pore density flow method was proposed, and the discrete element analysis software MatDEM was improved to realize the simulation of the accumulation process of seabed sediment pore pressure. Based on the field test device and the mechanical parameters of the soil body, a discrete element model was established. By comparing field test and numerical simulation results, it was found that after applying the wave load to the seabed sediment, a higher pore pressure was generated in the surface soil body and gradually transferred to the deep layer. Under the action of cyclic wave load, the cumulative range of pore pressure between soil particles gradually increased. When the pore pressure accumulation time was long enough, the pore pressure in the soil layer converged to the average of the maximum and minimum loads applied. As the number of load cycles increased, the pore pressure at all depths increased cumulatively until the soil body liquefied and the internal soil particles became resuspended sediments. Under the action of periodic wave loads, the soil particles moved after being liquefied and suspended, and the shallow particles had a large displacement, and the overall performance of the soil was circular arc movement.
-
Key words:
- discrete element /
- numerical simulation /
- wave action /
- pore water pressure /
- MatDEM
-
图 1 离散颗粒堆积模型（a）、颗粒间法向弹簧力（b）和颗粒间切向弹簧力（c）
Fig. 1 Packing model of discrete element (a), normal spring force between particles (b), and shear spring force between particles (c)
图 2 离散元堆积颗粒（a）、孔隙流体域（b）和颗粒−孔隙系统（c）
Fig. 2 Discrete element stacked particles (a), pore fluid domain (b), and particle and pore system (c)
图 6 荷载循环1次（a）、10次（b）、20次（c）、40次（d）孔压分布
Fig. 6 Pore pressure distribution of load cycle 1 (a), 10 (b), 20 (c), 40 (d) times
图 7 循环荷载40次孔压累积
Fig. 7 Pore water pressure accumulation process under cyclic loading 40 times
表 1 海洋土体宏观力学性质
Tab. 1 Macro mechanical properties of ocean soil
力学性质 测试值 杨氏模量E/MPa 5.00 泊松比v 0.14 抗拉强度Tu/kPa 1.00 抗压强度Cu/kPa 10 内摩擦系数μi 0.5 
下载: 导出CSV
表 2 离散元微观力学参数
Tab. 2 Micro mechanical parameters of the discrete element
力学参数 平均值 法向刚度 Kn/(kN·m−1) 123 切向刚度 Ks/(kN·m−1) 48.7 断裂位移 Xb/m 1.40×10−6 抗剪力 Fs0/N 0.898 摩擦系数 μp 0.121
下载: 导出CSV
表 3 数值模拟与现场试验孔压数据对比
Tab. 3 Data comparison of pore pressure between numerical simulation and field test
深度/m 现场孔压/kPa 模拟孔压/kPa 0.05 0.585 0.652 0.12 0.799 1.513 0.20 1.890 1.858 0.30 1.635 1.814
下载: 导出CSV
-
[1] 常方强, 贾永刚. 黄河口粉质土海床液化过程的现场试验研究[J]. 土木工程学报, 2012, 45(1): 121−126.Chang Fangqiang, Jia Yonggang. In-situ test to study silt liquefaction at the subaqueous delta of Yellow River[J]. China Civil Engineering Journal, 2012, 45(1): 121−126. [2] Anderson D, Cox D, Mieras R, et al. Observations of wave-induced pore pressure gradients and bed level response on a surf zone sandbar[J]. Journal of Geophysical Research: Oceans, 2017, 122(6): 5169−5193. doi: 10.1002/2016JC012557 [3] Niu Jianwei, Xu Jishang, Dong Ping, et al. Pore water pressure responses in silty sediment bed under random wave action[J]. Scientific Reports, 2019, 9(1): 11685. doi: 10.1038/s41598-019-48119-y [4] 刘晓磊, 贾永刚, 郑杰文. 波浪导致黄河口海床沉积物超孔压响应现场试验研究[J]. 岩土力学, 2015, 36(11): 3055−3062.Liu Xiaolei, Jia Yonggang, Zheng Jiewen. In situ experiment of wave-induced excess pore pressure in the seabed sediment in Yellow River Estuary[J]. Rock and Soil Mechanics, 2015, 36(11): 3055−3062. [5] 张少同, 贾永刚, 刘晓磊, 等. 现代黄河三角洲沉积物动态变化过程的特征与机理[J]. 海洋地质与第四纪地质, 2016, 36(6): 33−44.Zhang Shaotong, Jia Yonggang, Liu Xiaolei, et al. Feature and mechanism of sediment dynamic changing processes in the Modern Yellow River Delta[J]. Marine Geology & Quaternary Geology, 2016, 36(6): 33−44. [6] 吕豪杰, 周香莲, 王建华. 波浪荷载作用下桩周土体孔隙水压力试验研究[J]. 上海交通大学学报, 2018, 52(7): 757−763.Lü Haojie, Zhou Xianglian, Wang Jianhua. Laboratory study of wave-induced pore pressures around the pile[J]. Journal of Shanghai Jiaotong University, 2018, 52(7): 757−763. [7] 宋玉鹏, 孙永福, 杜星, 等. 波浪作用下海底粉土孔隙水压力响应过程监测研究[J]. 海洋地质与第四纪地质, 2018, 38(2): 208−214.Song Yupeng, Sun Yongfu, Du Xing, et al. Monitoring of silt pore pressure responding process to wave action[J]. Marine Geology & Quaternary Geology, 2018, 38(2): 208−214. [8] 吴雷晔, 朱斌, 陈仁朋, 等. 波浪−海床−结构物相互作用离心模型试验及数值模拟[J]. 土木工程学报, 2019, 52(S2): 186−192.Wu Leiye, Zhu Bin, Cheng Renpeng, et al. Centrifuge test and numerical simulation of wave-seabed-structure interaction[J]. China Civil Engineering Journal, 2019, 52(S2): 186−192. [9] 潘冬子, 王立忠, 潘存鸿. 粉质海床波浪响应的数值模拟及试验研究[J]. 岩土力学, 2008, 29(10): 2697−2700, 2707. doi: 10.3969/j.issn.1000-7598.2008.10.020Pan Dongzi, Wang Lizhong, Pan Cunhong. Numerical simulation and experimental investigation of wave-induced response in silty seabed[J]. Rock and Soil Mechanics, 2008, 29(10): 2697−2700, 2707. doi: 10.3969/j.issn.1000-7598.2008.10.020 [10] 刘涛, 冯秀丽, 林霖. 海底孔压对波浪响应试验研究及数值模拟[J]. 海洋学报, 2006, 28(3): 173−176.Liu Tao, Feng Xiuli, Lin Lin. Study of seabed pore water pressure based on in-situ test and numerical simulation[J]. Haiyang Xuebao, 2006, 28(3): 173−176. [11] 周援衡, 卢海斌, 陈智杰. 波浪作用下弹性海床孔隙水应力响应的数值模拟[J]. 水道港口, 2005, 26(2): 67−70. doi: 10.3969/j.issn.1005-8443.2005.02.001Zhou Yuanheng, Lu Haibin, Chen Zhijie. Numerical simulation of pore water pressure response of elastic seabed under wave loading[J]. Journal of Waterway and Harbor, 2005, 26(2): 67−70. doi: 10.3969/j.issn.1005-8443.2005.02.001 [12] Liu Chun, Xu Qiang, Shi Bin, et al. Mechanical properties and energy conversion of 3D close-packed lattice model for brittle rocks[J]. Computers & Geosciences, 2017, 103: 12−20. [13] 雷健, 潘保芝, 张丽华. 基于数字岩心和孔隙网络模型的微观渗流模拟研究进展[J]. 地球物理学进展, 2018, 33(2): 653−660. doi: 10.6038/pg2018BB0108Lei Jian, Pan Baozhi, Zhang Lihua. Advance of microscopic flow simulation based on digital cores and pore network[J]. Progress in Geophysics, 2018, 33(2): 653−660. doi: 10.6038/pg2018BB0108 [14] 刘春, 乐天呈, 施斌, 等. 颗粒离散元法工程应用的三大问题探讨[J]. 岩石力学与工程学报, 2020, 39(6): 1142−1152.Liu Chun, Le Tiancheng, Shi Bin, et al. Discussion on three major problems of engineering application of the particle discrete element method[J]. Chinese Journal of Rock Mechanics and Engineering, 2020, 39(6): 1142−1152. [15] 常方强, 贾永刚. 黄河口水下斜坡波致圆弧振荡剪切破坏分析[J]. 海洋学报, 2010, 32(5): 175−179.Chang Fangqiang, Jia Yonggang. The analysis on the arc oscillatory shear failure induced by wave on the seabed in the Huanghe Estuary[J]. Haiyang Xuebao, 2010, 32(5): 175−179. [16] 刘春, 范宣梅, 朱晨光, 等. 三维大规模滑坡离散元建模与模拟研究——以茂县新磨村滑坡为例[J]. 工程地质学报, 2019, 27(6): 1362−1370.Liu Chun, Fan Xuanmei, Zhu Chenguang, et al. Discrete element modeling and simulation of 3-dimensional large-scale landslide-taking Xinmocun landslide as an example[J]. Journal of Engineering Geology, 2019, 27(6): 1362−1370. [17] Zhang Jisheng, Tong Linlong, Zheng Jinhai, et al. Effects of soil-resistance damping on wave-induced pore pressure accumulation around a composite breakwater[J]. Journal of Coastal Research, 2018, 34(3): 573−585. doi: 10.2112/JCOASTRES-D-17-00033.1 [18] Liu Xiaoli, Cui Haonan, Jeng D S, et al. A coupled mathematical model for accumulation of wave-induced pore water pressure and its application[J]. Coastal Engineering, 2019, 154: 103577. doi: 10.1016/j.coastaleng.2019.103577 -
图(10) / 表(3)
计量
- 文章访问数: 488
- HTML全文浏览量: 164
- PDF下载量: 29
- 被引次数: 0
