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中国地质大学(武汉)课题组近日在《Journal of Rock Mechanics and Geotechnical Engineering》期刊发表了题为“Seepage and deformation characteristics of sliding-zone soils under cyclic seepage pressure”(循环4 n3 R Y* W3 o2 j3 [2 ]# l1 R
渗流压力下滑带土的渗流与变形特性)的学术论文。本研究运用GDS应力路径三轴仪、NMR孔结构测试系统及μ-CT平台,对三峡库区马家沟滑坡滑带原状与重塑土开展稳态、循环渗压试验,提出“物化-结构协同劣化”模型,系统揭示循环渗压下天然结构-渗流-变形耦合机制,证实循环渗压使滑带土累积体变与不可恢复体变分别较稳态渗压提高1.6倍与近无穷倍(稳态几乎可恢复),为库岸滑坡稳定性评价提供直接依据。7 a5 Q) v5 C! q G! }
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https://doi.org/10.1016/j.jrmge.2025.01.059! j* |* p' D! T. p4 |, \
*论文版权归原作者和出版方所有,本文仅为学习交流。, B* ^. N- X" F( d, `9 @$ c% Y
以下是对这项成果的简要介绍:
$ [+ G& r* a X" O9 p论文摘要8 o+ r* N% B1 U; N6 O
水库区大量滑坡失稳事件归因于水位波动,后者常在土体内部诱发循环变化的渗流压力。在此类复杂循环渗流条件下,滑带土的水-力行为与稳定渗流情形显著不同,然而其渗流特性与变形规律尚未被充分理解。本研究在等向固结条件下开展循环渗压试验,探讨滑带土渗透系数与体积应变的变化。1 v3 S% ~& z/ y7 b7 J3 ?& o
结果表明:试样渗透系数在循环渗压作用下出现波动,波动幅度随渗压幅值增大而增强,随围压升高而减弱;体积应变亦呈显著波动,其幅值随渗压幅值增大而加剧,累计体积应变与不可恢复体积应变均高于稳定渗流情形。随后,将滞回圈划分为三类,分别对应不同的变形特征。最后,综合考虑物化反应对孔隙结构的影响,揭示了循环渗压作用下滑带土的微观机制,以更好地阐释其渗流特性与变形行为的内在机理。研究成果为准确评估水位波动条件下水库滑坡稳定性提供了理论依据。& ^4 y, F" }4 [! q
试验设备
2 k" S8 e/ e# W& K2 r$ }3 V t本研究使用了GDS应力路径三轴仪STDTTS等设备。2 Z8 q: z) ~7 y/ X7 V7 E
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相关图表
$ q( K; j$ Y0 b* c) |) T+ R*图表为论文截图,版权归论文原作者和出版方所有,本文仅为学习交流。
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Fig. 1.Schematic illustration of reservoir landslide and stress condition of sliding-zone soil under periodic water fluctuations and seasonal rainfall in the TGRA.' ^! @+ j/ D$ ]; S
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" g/ v! h3 v) ^0 a) gFig. 2.Study area: (a) Map of the TGRA; (b) Three-dimensional (3D) structure of Majiagou landslide; and (c) Vertical profile of landslide.
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Fig. 3. Grain size distribution. g1 w3 H7 ^, }8 [/ V/ U* T5 W
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Fig. 4. Diagram of (a) GDS triaxial system and (b) boundary conditions of the sample# |$ e1 c2 D' u
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Fig. 5. Loading process for consolidation tests under cyclic seepage pressure conditions.' s V, x3 D( h" d% s6 l' {
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Fig. 6. Correction of volume change during the loading stage.
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$ n% t! \) g* \3 I( i1 rFig. 7. Changes in hydraulic conductivity with time for sliding-zone soil under cyclic seepage pressure and steady seepage pressure: (a) 100 kPa, (b) 150 kPa, (c) 200 kPa, and (d) 300 kPa.. h5 ]" E3 s6 z2 q) M8 g3 v7 K& S
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# l5 D' t, [1 U$ K$ _& sFig. 8. Change in average hydraulic conductivity with the number of cycles.) E# K; R. k( {5 P, g& W$ O
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Fig. 9. Change in hydraulic conductivity with confining pressure.9 l& E q7 G3 J3 f2 |
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5 L/ L; p, c2 o5 z& E" H, DFig. 10. Variation in volumetric strain with time for sliding-zone soil under cyclic seepage pressure and steady seepage pressure: (a) 100 kPa, (b) 150 kPa, (c) 200 kPa, and (d) 300 kPa.
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Fig. 11. Change in volumetric strain with time for sliding-zone soil at a confining pressure of 350 kPa.
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) g( v" @2 x! r5 g; ^8 @( N vFig. 12. Variation in cumulative volumetric strain with confining pressure for sliding-zone soil: (a) Loading stage; and (b) Unloading stage.
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t9 ]0 h9 ^( ?8 w5 W, eFig. 13. Change in irrecoverable volumetric strain with confining pressure for sliding-zone soil.
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Fig. 14. Hysteresis loops under cyclic seepage pressure at a 350 kPa confining pressure for sliding-zone soil: (a) 100 kPa, (b) 150 kPa, (c) 200 kPa, and (d) 300 kPa.
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Fig. 15. Change in the porosity with seepage pressure amplitude for sliding-zone soil samples.
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0 x/ ]& N8 b5 l" L) LFig. 16. Change in the pore size distribution of sliding-zone soil samples. S – Steady seepage pressure; C – Cyclic seepage pressure; L – After seepage; B – Before seepage.
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3 g$ N6 b7 n# m0 PFig. 17. Change in the percentage of pore volume.
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4 u0 i+ S. s: u; @Fig. 18. Schematic depicting (a) soil particle structure, (b) water types on the clay particle surface, and (c) particle association./ @/ L' Z6 K# F2 C$ q+ q Y1 ~
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Fig. 19. Characteristics of mesostructure of sliding-zone soil samples.* P; u+ [: i# F" T, X2 C5 B
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Fig. 20. The physicochemical reactions in the microstructure of sliding-zone soil under cyclic seepage pressure. m) N$ B. a6 D1 |! f' {7 r
研究结论
1 b0 z* X2 G7 j! V本研究定量阐明了循环渗压下滑带土的渗流特性与变形行为,并揭示了孔隙尺度的微观机制。主要结论如下:
0 c( n. p. E8 Y# ]: \(1) 通过分析渗透系数变化,阐明了循环渗压下滑带土的渗流特性:渗透系数在循环渗压下显著波动,且整体高于稳态渗压;循环加载过程中,平均渗透系数随循环次数增加先降后稳。
- U# i7 H. p% Y% }( G2 K(2) 通过体应变演化与滞回曲线特征,定量表征了循环渗压下滑带土的变形行为:体应变持续波动增长,无稳定阶段,幅度显著大于稳态渗压;依据滞回环形态划分为三类,进一步揭示了变形特征。5 ^! N J: q4 C& H9 Q {) x
(3) 提出了考虑物化反应的滑带土孔隙结构微观机制:水化膨胀、颗粒聚集、矿物溶解与结构破坏导致粒内孔隙与宏孔减少、粒间孔隙与团聚体孔隙增多,这是渗流-变形特性变化的根本原因。% C5 l' P, r% D4 O& L* ]
研究成果为揭示库岸滑坡滑带土在库水运行循环渗压作用下的响应机制提供了新见解,未来需进一步阐明复杂应力状态下滑带土工程性质响应的深层机制。 |
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