Experimental investigation on cyclic failure criteria for marine clay based on energy method
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摘要: 海洋黏土循环强度的合理确定对确保海洋结构物全寿命服役期的稳定性有重要意义。针对不同塑性指数IP长江口原状海洋黏土，开展了不同循环应力比CSR条件下的常体积循环单剪试验，结合能量法探究了原状海洋黏土的循环破坏准则。研究结果表明：原状海洋黏土存在门槛循环应力比CSRth，当CSR < CSRth时，单圈能量耗散Wi只在较小范围内线性发展，土体不会发生循环破坏；当CSR > CSRth时，Wi随循环振次N的发展曲线因土体结构的严重破坏而出现突变点，并以该点作为破坏点确定了破坏振次Nf和破坏双幅剪应变γDA,f；长江口原状海洋黏土的CSRth随IP增大增长呈现幂函数关系。随着CSR和IP的增大，Wi和γDA,f均逐渐增大，Nf逐渐减小。γDA,f/IP1.5 -CSR-CSRth的数据点分布在一条较窄的范围内，且γDA,f/IP1.5随CSR-CSRth增长服从线性函数关系，提出了适用于不同海域原状海洋黏土γDA,f的评价方法。Abstract: The reasonable determination of the cyclic strength of marine clay is critical for ensuring the stability of marine structures throughout their service life. In order to study the cyclic failure criteria for the marine clay, a series of constant-volume cyclic direct simple shear tests are performed on the undisturbed saturated marine clay in the Yangtze River Estuary with different plasticity indexes (IP) under different cyclic stress ratios (CSRs). The cyclic responses of the marine clay specimens are presented. The cyclic failure criteria are investigated by employing the energy method. The results indicate that there is a threshold cyclic stress ratio (CSRth) in the undisturbed marine clay. When the CSR is smaller than the CSRth, the energy dissipation per cycle (Wi) develops linearly only within a limited range that does not contribute to the cyclic failure of marine clay. However, when the CSR exceeds the CSRth, the development curve of Wi with the number of cycles (N) shows an inflection point due to the serious damage of the soil structures. This point serves as the critical point for cyclic failure to determine the number of cycles to failure (Nf) and the double-amplitude shear strain to failure (γDA,f). The CSRth of the marine clay in the Yangtze River Estuary exhibits a power function relationship with the increasing IP. Additionally, with the increasing CSR and IP, both Wi and γDA,f tend to increase, while the Nf gradually decreases. Furthermore, the data points of γDA,f/IP1.5 ~ CSR-CSRth for all the tests are distributed in a narrow band, and a virtually positive linear relationship exists between the γDA,f/IP1.5and CSR-CSRth. Finally, a γDA,f evaluation method applicable to the marine clay in different seas is proposed for practical geotechnical engineering.
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0. 引言
随着中国西部大开发和国家“一带一路”倡议的实施,越来越多架空输电线路工程需建设在黄土地区。黄土是一类特殊土地基[1-2],具有大厚度、强湿陷性特点。架空输电线路基础在黄土浸水后将产生较大湿陷性变形,同时这种湿陷变形将引起负摩擦力作用于基础,造成基础产生附加上拔作用[3-6]。与此同时,湿陷性变形也容易造成基础不均匀沉降,对上部杆塔结构产生较大附加应力,影响杆塔结构安全,黄土湿陷性造成电力工程损失屡见不鲜。如2020年8月,甘肃秦安地区出现集中暴雨,导致麦积山—宝鸡750 kV输电线路#124塔的桩基不均匀沉降,致使基础和铁塔主材严重变形,被迫新建3基新塔对原线路进行改造。
此外,架空输电线路基础呈点状分布,大型施工装备进场往往受到地形和道路运输条件限制,使得中国输电线路基础尚以人力施工为主。新型基础型式研发、基础施工装备小型化、基础工程防灾减灾,一直是黄土地区架空输电线路建设的热点和难点[7]。微型桩是指桩径小于350 mm的小直径桩[8-9],其布置形式灵活,施工机械设备小型化,可较好适用于各种类土质条件,与同体积灌注桩相比承载力较高等特点,已在黄土地区电力工程中得到应用。
随外界条件变化,架空输电线路基础需承受同时拉／压荷载作用,微型桩基础抗压和抗拔承载性能至关重要。周俊鹏等[10]开展了黄土地基光伏电站微型桩抗压与抗拔桩对比试验研究。然而,湿陷是黄土地区的一种普遍现象,湿陷变形的充分完成需要足够的浸入水量和浸水时间,黄土浸水后湿陷特性及其对基础承载性能影响一直是科研和工程设计的关键问题。武小鹏等[11]和黄雪峰等[12]通过大厚度现场试坑浸水试验研究了黄土湿陷变形发展规律,分析了水在原状黄土中的扩散形态与浸水影响范围。邵生俊等[13]通过开展大厚度湿陷性黄土隧道的现场浸水试验,分析了黄土湿陷变形对隧道衬砌结构承载性能的影响机制。张延杰等[14]研究了湿陷性黄土地下连续墙竖向极限承载力组成以及浸水后墙身轴力和负摩阻力分布特征。张西等[15]基于黄土直柱掏挖基础浸水静载试验成果,对黄土地基杆塔基础设计进行了优化。总体上看,开展浸水饱和与天然状态下黄土微型桩基础竖向抗压和抗拔承载力对比试验较少。本文选择甘肃地区2个湿陷性黄土场地,设计了一种微型桩周围黄土浸水饱和方案,并完成了黄土浸水饱和与天然含水率状态下微型桩单桩抗压抗拔和群桩抗压对比试验,为黄土微型桩基础工程应用提供参考。
1. 黄土试验场地及其物理力学性质
本文2个黄土试验场地均在甘肃省,分别位于定西市大坪村和榆中县车道岭。通过探井取样获得原状黄土试样,并开展黄土物理力学性质试验。大坪村和车道岭场地探井取样深度分别为0.7～8.7 m和1.0～8.0 m,取样间隔均为1.0 m。
试验场地黄土粒径分布范围0.001～0.5 mm。图1为试验场地黄土粒径级配累积曲线,相应试验场地黄土颗粒的特征粒径也列于图1。
图2为试验场地天然含水率、重度和相对质量密度实测值随深度变化曲线,黄土含水率、重度、相对质量密度变化范围分别为5.0%～12.7%,12.8 kN/m3～13.9 kN/m3和2.60～2.85。表1给出了2个试验场地黄土液塑限指标值。
表 1 试验场地黄土液塑限指标Table 1. Atterberg limit test results场地名称 液塑限指标 液限/% 塑限/% 塑性指数 大坪村 32.6 18.1 14.5 车道岭 39.8 21.3 18.5 2个试验场地黄土抗剪强度试验方法略有不同。大坪村场地采用探井取原状土样,进行室内快剪试验,车道岭场地开展原位直剪试验。大坪村试验场地黄土抗剪强度随深度变化规律如图3所示,黏聚强度与内摩擦角变化范围分别为16.4～26.9 kPa和24.0°～29.0°,相应均值分别为21.5 kPa和26.8°。图4为车道岭场地现场原位直剪试验原理及不同深度土体在不同正应力水平下的剪切应力-剪切位移曲线。土体剪切面深度分别为0.9,1.5,2.0 m,每深度原位直剪试样3个,其长×宽×高均为0.6 m×0.6 m×0.4 m。根据图4试验结果,按Mohr-Columb强度准则拟合得到车道岭试验场地0.9,1.5,2.0 m深度处黄土黏聚强度分别为12.4,12.7,14.2 kPa,内摩擦角分别为30.2°,27.5°和38.2°。
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图 3 大坪村试验场地抗剪强度随深度变化规律Figure 3. Laboratory measured results of direct shear test results for loess profile at Dapingcun site![]()
图 4 车道岭现场原位直剪试验原理及不同深度土体剪切应力-剪切位移曲线Figure 4. Schematic layout and shear stress versus displacement curves for in-situ direct shear tests at Chedaoling此外,对每个场地探井原状样进行3个湿陷系数试验,取平均值绘制图5所示的湿陷系数随深度变化曲线。结果表明：大坪村和车道岭试验场地黄土均有剧烈湿陷性,且湿陷性总体上随深度增加略有减小。
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图 5 试验场地黄土湿陷性系数随深度变化Figure 5. Loess collapse index and corresponding classification of test results for soil profile2. 试验方案
2.1 试验基础
（1）微型桩单桩
微型桩单桩试验在大坪村试验场地完成,如表2所示。天然状态下黄土微型桩单桩上拔和下压试验各3个,相应桩长l为6.0,8.0,10.0 m。浸水饱和状态下黄土微型桩上拔和下压试验各2个,桩长l=8.0 m。所有试验基础桩径d均为0.30 m。为便于试验荷载施加与位移传感器布置,所有试验基础桩顶设计成方形,相应的长×宽×高均为0.6 m×0.6 m×0.6 m。
表 2 微型桩单桩试验基础及其试验结果Table 2. Basic information on single and group micropiles and load-displacement results at two test sites基础型式 试验地点 荷载类型 基础编号 地基状态 l/m d/m Q u/kN su/mm 桩侧平均极限侧阻力/kPa 计算值 平均值 单桩 大坪村 上拔 MP1U 天然 6.0 0.30 220 4.91 38.94 44.82 MP2U 天然 8.0 0.30 300 7.12 39.79 MP3U 天然 10.0 0.30 525 15.66 55.73 MP4U 浸水饱和 8.0 0.30 150 8.43 19.89 19.23 MP5U 浸水饱和 8.0 0.30 150 8.55 18.57 下压 MP1C 天然 6.0 0.30 335 6.85 63.72 60.15 MP2C 天然 8.0 0.30 397 7.46 53.05 MP3C 天然 10.0 0.30 602 7.16 63.69 MP4C 浸水饱和 8.0 0.30 120 4.61 15.92 15.92 MP5C 浸水饱和 8.0 0.30 119 4.35 15.92 群桩 车道岭 下压 GMP1C 天然 8.0 0.30 1400 23.56 － － GMP2C 浸水饱和 8.0 0.30 360 3.84 （2）微型桩群桩
微型桩群桩试验在车道岭场地完成,黄土天然状态和浸水饱和状态下群桩试验各1个,且基础结构尺寸完全相同,均采用2×2群桩布置方式,其中l=8.0 m,d=0.30 m,桩间距均为3d。承台均为方形,其边长1.7 m,厚度0.70 m。
2.2 黄土浸水方案与实施
以图6所示大坪村微型桩单桩试验为例,介绍试验单桩周围黄土浸水饱和方案。
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图 6 试验基础周围黄土浸水饱和方案Figure 6. Arrangement of loess prewetting until completely soaked and saturated condition by ponding浸水前以试验单桩为中心,先开挖一上口径1500 mm、下口径1200 mm、深600 mm土坑,然后在坑内直径1000 mm圆周上,按90°等分角布置4个直径100 mm钻孔,钻孔深度比试验桩长大0.5 m。在每个钻孔内布置一根直径20 mm的PVC管,管口高出坑底黄土200 mm。自PVC管的上孔口开始,向下每200 mm间隔的横截面上均匀布置4个直径5 mm透水预留孔。黄土钻孔和PVC管外壁之间空隙采用中细沙密实填充,并保持PVC管的垂直度,最后在坑底及坑口周围布置塑料布用于隔水。
浸水过程中通过水车向土坑内注水,当水面高于PVC管口时,水将进入PVC管,进而通过PVC管预留透水孔和钻孔内中细沙向桩周和桩底的黄土地基渗透。注水过程中维持坑内水位与地表始终齐平。
图7给出了总灌水方量Q与浸水时间t的关系曲线。自开始灌水至灌水后95 h,灌水方量随时间呈近似线性增长关系,并可用Q=0.465t进行拟合,即相当于按0.465 m3/h匀速灌水。待浸水时间达到95 h后,浸水量基本趋于稳定,增长缓慢。此时,可近似认为试验基础周围的黄土处于浸水饱和状态。
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图 7 灌水量随浸水时间变化曲线Figure 7. Relationship between total poured water volume and prewetting time2.3 加载系统与方案
微型桩单桩下压上拔以及微型桩群桩试验加载系统均采用锚桩法设计。所有基础试验反力钢梁长12 m,反力基础间距10 m。通过液压千斤顶及其控制系统施加荷载,具有自动加载、恒载与补载功能。
现场所有试验均采用慢速维持荷载法。试验前,按基础最大预估荷载值1/10为增量进行荷载分级。第1次加载量取荷载分级增量2倍,以后逐级等量加载。
3. 试验结果与分析
3.1 基础荷载-位移特性及其极限承载力确定
图8给出了浸水饱和与天然状态下微型桩单桩抗压抗拔和群桩抗压对比试验的荷载-位移实测曲线。
对比分析图中各试验基础荷载-位移曲线可知：2种状态下微型桩单桩和群桩基础荷载-位移曲线变化规律不同。天然状态条件下,微型桩单桩抗压抗拔和群桩抗压基础荷载-位移曲线总体呈图9所示“缓变型”3阶段变化规律：初始弹性段（OL1段）,位移随荷载增加非线性变化的弹塑性曲线过渡段（L1L2段）和破坏直线段（L2点以后）。然而,浸水饱和黄土地基微型桩单桩抗压抗拔和群桩抗压基础荷载-位移曲线均呈图9所示“陡变型”变化规律。
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图 9 试验基础荷载-位移曲线特征及其极限承载力确定Figure 9. Characteristics of measured load-displacement curves and definition of ultimate load capacity根据试验基础荷载-位移曲线特征,取图9所示“缓变型”荷载-位移曲线弹塑性过渡段终点L2和“陡变型”荷载-位移曲线陡变起点（近似为陡降段荷载-位移的渐进线）所对应荷载作为相应试验工况下的基础极限承载力,记为Qu,其所对应位移记为su。各试验基础极限承载力和位移分别如表2所示。
试验结果表明：黄土天然状态下,相同微型桩单桩抗拔极限承载为抗压极限承载力的66%～87%。相同荷载工况与相同基础尺寸条件下,浸水饱和后黄土微型桩单桩和群桩承载力都要远低于天然地基条件下相应的微型桩基础。对相同微型桩单桩而言,黄土浸水饱和后的下压极限承载力平均下降70%,抗拔极限承载力平均下降50%,而相同群桩基础下压极限承载力则降低约75%。
3.2 单桩轴力分布与桩侧极限侧阻力平均值计算
为测试上拔下压荷载作用下微型桩轴力分布特征,分别在其不同深度设置应变片测试相应截面处轴力。图10给出了桩长均为8 m抗拔（MP2U和MP5U）和抗压（MP2C和MP5C）微型桩单桩在天然含水率和浸水饱和状态下桩身轴力分布对比。图10结果表明：黄土天然含水率和浸水饱和状态下,相同荷载工况下桩身轴力分布规律基本相同,黄土抗压微型桩呈摩擦端承桩性状,而相应抗拔微型桩则仅呈摩擦桩性状。天然含水率和浸水饱和黄土中微型桩单桩桩端阻力可分担桩顶荷载的比例为10%～15%,这与软土微型桩下压承载力试验成果一致[16-19]。
根据各微型桩单桩极限荷载试验值,分别计算各单桩平均极限侧阻力如表2所示。天然条件下黄土下压极限侧阻力均值为60.15 kPa,而对应上拔极限侧阻力均值为44.82 kPa,天然黄土的下压极限侧阻力比上拔极限侧阻力高25.5%。然而,当黄土浸水饱和后,下压极限侧阻力均值为15.92 kPa,而对应上拔极限侧阻力均值为19.23 kPa。浸水饱和条件下,黄土上拔极限侧阻力和下压极限侧阻分别下降57.1%和73.5%。
4. 结论
（1）浸水饱和条件下,黄土微型桩单桩抗压抗拔和群桩抗压实测荷载-位移曲线均呈“陡变型”变化规律,明显不同于黄土天然状态下相应荷载-位移曲线的“缓变型”3阶段变化规律：初始弹性段、弹塑性曲线过渡段和破坏直线段。
（2）当黄土分别处于浸水饱和与天然含水率时,下压微型桩单桩桩端阻力所分担的桩顶荷载比例均为10%～15%,而相应抗拔微型桩则呈摩擦桩性状。天然状态下黄土微型桩单桩抗拔极限承载力为抗压极限承载力的66%～87%。
（3）黄土浸水饱和后,同桩长微型桩单桩下压极限承载力下降70%,抗拔极限承载力下降50%,而2×2微型桩群桩基础下压极限承载力则降低约75%。浸水饱和使黄土微型桩下压极限承载力损失远高于相应基础的上拔极限承载力,工程中应予以高度重视。
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图 2 长江口取样场地地理位置（来源：谷歌地图）
Figure 2. Geographical location of sampling site in Yangtze River Estuary (Base map data © 2023 Google)
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图 4 代表性试样Y8-3剪应变时程和应力应变曲线
Figure 4. Shear strain time-history curves and shear stress-shear strain curves of specimen Y8-3
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图 5 代表性试样的循环剪应变和双幅剪应变时程曲线
Figure 5. Typical time-history curves of cyclic shear strain and double-amplitude shear strain of specimens
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图 6 代表性试样Y8-3的法向应力和超静孔压时程
Figure 6. Typical time-history curves of normal stress and excess pore water pressure for specimen Y8-3
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图 7 代表性海洋黏土的超静孔压比时程曲线(CSR = 0.18)
Figure 7. Typical time-history curves of excess pore water pressure ratio of marine clay (CSR=0.18)
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图 9 海洋黏土单圈能量耗散与循环振次的关系曲线
Figure 9. Relationship curves of energy dissipation per cycle versus number of cycles of marine clays
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图 10 循环破坏振次确定方法示意图
Figure 10. Sketch of method for determining number of cycles to failure
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图 11 试样Y1的循环应力比CSR与破坏振次Nf的关系
Figure 11. Relationship between CSR and Nf of specimen Y1
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图 12 长江口海洋黏土的循环强度曲线
Figure 12. Curves of cyclic strength of marine clay in Yangtze River Estuary
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图 13 长江口海洋黏土CSRth随IP的变化
Figure 13. Variation of CSRth with IP of marine clay in Yangtze River Estuary
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图 14 长江入海口海洋黏土γDA,f随CSR和IP的变化云图
Figure 14. Variation of γDA,f with CSR of marine clay in Yangtze River Estuary
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图 15 长江入海口海洋黏土γDA,f/IP1.5随CSR-CSRth的变化
Figure 15. Variation of γDA,f/IP1.5 with CSR-CSRth of marine clay in Yangtze River Estuary
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图 16 辽东湾海洋黏土CSR随Nf的变化及γDA,f预测值与实测值的对比
Figure 16. Variation of CSR with Nf and comparison of predicted and measured values of γDA,f of marine clay in Liaodong Bay
表 1 循环单剪仪传感器的量程、误差以及精度
Table 1 Measuring ranges, errors and precisions of sensors for cyclic direct simple shear test apparatus
传感器 量程 误差 精度 法向荷重传感器 5 kN 0.1%FS 0.2 N 第一剪切荷重传感器 5 kN 0.1% FS 0.2 N 第二剪切荷重传感器 5 kN 0.1% FS 0.2 N LVDT法向位移传感器 ± 2.5 mm 0.1% FS 0.1 μm LVDT剪切位移传感器 ± 10 mm 0.1% FS 0.4 μm 加载频率 ≤5 Hz — — 位移传感器 ± 25 mm 0.1% FS 0.8 μm 注：FS =满量程。 
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表 2 海洋黏土基本物理指标
Table 2 Basic physical properties of marine clay
取样区域 土样编号 海床以下深度H/m 相对质量密度Gs 天然含水率w0/% 天然密度ρ0/(g·cm-3) 初始孔隙比e0 饱和度Sr/% 塑限wp/% 液限wL/% 塑性指数IP 土类 长江入海口 Y1 6.6 2.71 37.85 1.82 1.05 97.78 23.8 81.6 57.8 CH Y2 8.6 2.65 40.10 1.79 1.07 99.41 30.9 71.0 40.1 CH Y3 16.6 2.69 41.21 1.79 1.12 98.60 30.2 65.6 35.4 CH Y4 7.6 2.69 37.52 1.83 1.03 98.33 27.5 62.3 34.8 CH Y5 22.0 2.70 39.28 1.81 1.07 98.75 26.4 58.5 32.1 CH Y6 28.1 2.71 38.56 1.82 1.06 98.49 29.2 60.0 30.8 CH Y7 15.1 2.69 40.12 1.80 1.09 97.81 25.4 48.9 23.5 CL Y8 16.6 2.68 37.80 1.82 1.03 98.38 23.8 39.9 16.1 CL Y9 20.6 2.68 39.11 1.78 1.10 95.46 18.4 34.7 16.3 CL Y10 19.2 2.69 44.80 1.76 1.21 99.68 19.3 30.8 11.5 CL 辽东湾营口段近海域 L1 17.3 2.68 40.50 1.79 1.11 98.17 16.7 32.8 16.1 CL L2 35.6 2.65 34.60 1.85 0.93 98.17 23.7 37.5 13.8 CL L3 55.6 2.67 33.20 1.85 0.92 96.18 21.7 38.2 16.5 CL 注：辽东湾营口段近海域的试样仅作验证用。
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表 3 循环单剪试验方案
Table 3 Schemes for cyclic direct simple shear tests
试样编号 σv/kPa CSR wc/% ec Δe/e0 质量等级 Nf/次 γDA, f/% 试样编号 σv/kPa CSR wc/% ec Δe/e0 质量等级 Nf/次 γDA, f/% Y1-1 50 0.202 36.55 1.013 0.034 1 664 6.61 Y6-1 190 0.152 35.94 0.989 0.068 2 > 1000 — Y1-2 0.221 36.62 1.015 0.032 1 237 7.83 Y6-2 0.178 36.09 0.993 0.064 2 330 6.26 Y1-3 0.248 36.62 1.015 0.032 1 81 8.53 Y6-3 0.202 36.02 0.991 0.066 2 60 7.08 Y1-4 0.271 36.73 1.018 0.029 1 47 9.61 Y6-4 0.221 35.87 0.987 0.070 2 20 8.11 Y2-1 60 0.170 36.94 1.007 0.058 2 > 1000 — Y7-1 100 0.139 37.61 1.042 0.043 2 > 1000 — Y2-2 0.201 36.68 1.000 0.065 2 223 6.94 Y7-2 0.158 37.50 1.039 0.046 2 657 5.08 Y2-3 0.221 36.79 1.003 0.062 2 42 7.85 Y7-3 0.181 36.56 1.013 0.070 2 67 6.50 Y2-4 0.249 36.57 0.997 0.068 2 20 8.94 Y7-4 0.221 36.85 1.021 0.062 2 16 8.18 Y3-1 110 0.164 37.55 1.032 0.082 3 > 1000 — Y8-1 120 0.124 36.30 1.000 0.029 1 > 1000 — Y3-2 0.182 37.88 1.041 0.074 3 654 6.38 Y8-2 0.148 36.12 0.995 0.034 1 621 5.27 Y3-3 0.199 38.31 1.053 0.063 2 188 6.80 Y8-3 0.179 36.05 0.993 0.035 1 51 6.83 Y3-4 0.219 38.09 1.047 0.069 2 70 7.46 Y8-4 0.221 35.94 0.990 0.038 1 5 8.23 Y4-1 50 0.162 35.99 0.992 0.033 1 > 1000 — Y9-1 140 0.124 35.72 1.014 0.076 3 > 1000 — Y4-2 0.181 35.27 0.972 0.052 2 486 6.18 Y9-2 0.150 35.89 1.019 0.072 3 638 5.16 Y4-3 0.203 35.38 0.975 0.049 1 103 7.84 Y9-3 0.180 36.00 1.022 0.069 2 51 6.74 Y4-4 0.222 34.83 0.960 0.064 2 30 8.92 Y9-4 0.221 36.39 1.033 0.059 2 8 8.13 Y5-1 145 0.153 36.48 1.001 0.068 2 > 1000 — Y10-1 130 0.105 42.24 1.140 0.058 2 > 1000 — Y5-2 0.182 36.69 1.007 0.063 2 304 6.10 Y10-2 0.117 42.37 1.152 0.048 2 596 4.41 Y5-3 0.205 37.17 1.020 0.050 2 86 7.60 Y10-3 0.148 41.82 1.137 0.059 2 159 5.89 Y5-4 0.225 36.84 1.011 0.059 2 25 9.09 Y10-4 0.179 42.23 1.148 0.050 2 19 6.99 L1-1 120 0.151 34.52 0.953 0.138 4 382 5.06 L3-1 370 0.163 27.08 0.763 0.149 4 173 5.22 L1-2 0.181 33.69 0.930 0.159 4 46 6.39 L3-2 0.180 26.90 0.758 0.177 4 40 6.31 L1-3 0.202 33.83 0.934 0.155 4 13 7.43 L3-3 0.201 26.97 0.760 0.152 4 5 7.28 L2-1 240 0.180 31.66 0.874 0.057 2 429 5.58 Y1-5 50 0.195 36.37 1.008 0.039 1 1342 4.88 L2-2 0.200 31.23 0.862 0.062 2 64 6.46 Y1-6 0.185 36.19 1.003 0.044 2 > 2000 — L2-3 0.222 31.52 0.870 0.054 2 33 7.46 Y1-7 0.175 36.01 0.998 0.049 2 > 1000 — 注：Y1 ~ Y10为长江入海口海洋黏土，L1 ~ L3为辽东湾营口段近海域海洋黏土，其中Y1-5 ~ Y1-7和L1 ~ L3仅作验证使用，试样质量等级评价详见表 4。wc为固结后试样的含水率；Δe为固结前后试样孔隙比的变化量；Nf为达到循环破坏标准所需的循环振次；γDA, f为达到循环破坏标准所需的循环破坏双幅剪应变。σv和CSR为试验的控制变量，wc，ec和Δe/e0为固结完成后的计算结果，Nf和γDA, f为测试结果。
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OCR Δe/e0 1 ~ 2 < 0.04 0.04 ~ 0.07 0.07 ~ 0.14 > 0.14 2 ~ 4 < 0.03 0.03 ~ 0.05 0.05 ~ 0.10 > 0.10 质量等级 1 2 3 4 试样质量 好~极好 好~差 差 极差 扰动程度 不扰动 轻微扰动 显著扰动 完全扰动
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表 5 不同海域海洋黏土的拟合方程参数
Table 5 Fitting parameters for marine clay in different seas
试样编号 a b CSRth 可决系数R2 Y1 1.088 -0.675 0.191 0.982 Y2 0.313 -0.479 0.173 0.927 Y3 0.844 -0.671 0.172 0.957 Y4 0.280 -0.502 0.170 0.964 Y5 0.214 -0.396 0.160 0.966 Y6 0.186 -0.366 0.158 0.999 Y7 0.336 -0.547 0.148 0.991 Y8 0.143 -0.315 0.135 0.984 Y9 0.182 -0.346 0.132 0.994 Y10 0.221 -0.402 0.112 0.804 L1 0.201 -0.494 0.135 0.920 L2 0.284 -0.454 0.160 0.958 L3 0.146 -0.428 0.137 0.981
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