Experimental study on long-distance shear characteristics of fully weathered granite residual soil
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摘要:
近年来,随着全球气候变化和人类工程活动的加剧,我国东南地区因降雨引发的群发性滑坡事件频发,严重威胁着人民的生命和财产安全。全风化花岗岩残积土作为这类滑坡灾害的主要地质载体,深入研究其力学特性对于揭示群发性滑坡的孕育演化机制具有重要意义。文章选取全风化花岗岩残积土为研究对象,综合考虑正应力(20 kPa,50 kPa,100 kPa,150 kPa)、含水率(0,5%,10%,20%和30%)和剪切速率(10°/min,20°/min,40°/min,和80°/min)的影响,开展了一系列环剪试验,旨在探究全风化花岗岩残积土在滑坡启动阶段及长距离运动阶段的力学行为,尤其是长距离剪切特性。试验结果表明:土体的抗剪强度与含水率有着密切关系,随着含水率的增加,抗剪强度先降低后升高再降低,当含水率达到30%时,土体会出现明显的应变硬化现象。此外,土体的抗剪强度还与正应力、剪切速率和相对密实度密切相关。具体表现为,正应力越大,土体的峰值抗剪强度和残余抗剪强度越高,且对峰值抗剪强度的影响更为显著,同时应变软化现象也更加明显;剪切速率越大,土体的峰值抗剪强度和残余抗剪强度总体呈下降趋势,对峰值抗剪强度的影响大于对残余抗剪强度的影响,且表观黏度降低。研究成果可为群发滑坡灾害防治提供重要的理论支持。
Abstract:In recent years, with the intensification of global climate change and human engineering activities, mass landslide events triggered by rainfall have become frequent in southeast China, posing serious threats to the lives and property safety of the people. Fully weathered granite residual soil, as the main geological carrier of such landslide disasters, has significant importance for revealing the mechanisms of the formation and evolution of landslide clusters through in-depth study of its mechanical properties. This paper selects fully weathered granite residual soil as the research subject and considers the effects of normal stress (20 kPa, 50 kPa, 100 kPa, 150 kPa), water content (0, 5%, 10%, 20%, and 30%), and shear rate (10°/min, 20°/min, 40°/min, and 80°/min) to conduct a series of ring shear tests. The aim is to explore the mechanical behavior of fully weathered granite residual soil during the landslide initiation and long-distance movement phases, especially its long-distance shear characteristics. Experimental results show that the shear strength of the soil is closely related to its water content; as the water content increases, the shear strength initially decreases, then increases, and decreases again. At a water content of 30%, the soil exhibits significant strain hardening. In addition, the shear strength of the soil is closely related to normal stress, shear rate, and relative density. Specifically, the higher the normal stress, the higher the peak and residual shear strengths of the soil, with a more significant effect on peak shear strength and more pronounced strain softening; the higher the shear rate, the overall downward trend in peak and residual shear strengths, with a greater effect on peak shear strength than on the residual shear strength, and lower the apparent viscosity. The findings of this study provide important theoretical support for the prevention and control of mass landslide disasters within this region.
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Keywords:
- granite residual soil /
- ring shear test /
- water content /
- normal stress /
- shear rate /
- shear strength
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0. 引 言
全风化花岗岩残积土广泛分布于我国东南沿海地区[1 − 3],具有孔隙比大,浸水软化,易崩解,物理力学性质差等特性[4 − 7]。我国东南沿海地区地形以山地丘陵为主[8],雨量丰沛,气象灾害频繁。全风化花岗岩残积土广泛覆盖在区域内斜坡表面,厚度通常在6 m以内[9],是区域内滑坡的主要地质载体[10 − 14],在极端降雨条件下,极易在区域内引发群发性滑坡,严重威胁人民生命财产安全。并且随着经济建设的发展,切坡建房、修路等人类工程活动对自然坡体的扰动日益加剧,坡体失稳破坏现象更加频发。这类滑坡在失稳启动后,往往呈现出滑动—流动的动力演化过程[11],使其致灾效应进一步增大。
国内外学者针对全风化花岗岩残积土的物理力学特性,从不同方面开展了许多研究。例如,Lu等[7]采用直剪试验、X射线衍射试验和扫描电镜试验,研究了花岗岩残积土的力学性能和响应机理,并分析了其结构特征以及结构破坏机理;赵建军等[13]、尚彦军等[14]利用直剪试验和三轴试验,发现了全风化花岗岩剪胀现象与孔隙比和密实度相关;龙志东等[15]、许旭堂等[16]通过直剪试验,测试了不同初始干密度、含水率、垂直压力以及颗粒成分对抗剪强度指标的影响;郑武略等[17]开展三轴加卸荷试验,探讨了不同应力路径与不同卸荷水平下花岗岩残积土的力学特性;马勤国等[18]对不同含水率的原状和重塑花岗岩残积土展开三轴试验,研究其剪切变形特性;陈晓平等[19]应用反复剪切试验方法,研究高液限花岗岩残积土的剪切性状,发现其有应变硬化规律;Hu等[20]利用三轴试验研究了粉煤灰对花岗岩残积土的强度指数和渗透率的影响。
以上的研究中,大都基于直剪、三轴、反复剪切等试验来探究花岗岩残积土在小变形或有限变形阶段的力学性质,但针对滑坡长距离运动过程中的土体力学状态,上述相关试验方法并不能很好地反映土体的相关力学特性。因此,为了能够更好地模拟土体的长距离剪切破坏过程,深入探讨全风化花岗岩残积土的长距离剪切力学特性,采用环剪试验方法进行相关力学参数测试更为适宜[21 − 24]。例如,Wang等[25]利用环剪试验对滑坡前后土体进行测试,结果表明含水率的增加会降低黏土的抗剪强度;Bhat等[26]采用环剪装置对不同塑性黏土进行试验,得出了典型黏土的残余摩擦系数与剪切速率之间的关系;Wang等[27]通过改变正应力、含水率和剪切速率,对4种典型黏土进行环剪试验,发现含水率对残余强度的影响略大于剪切速率;Zhu等[28]通过环剪试验,研究了不同含水率的黄土滑带土在不同正应力和剪切速率条件下的剪切行为,结果发现滑坡的高速长距离运动机制与含水率和剪切速率的相互作用有关;Yuan等[29]利用环剪试验研究了改良黄土在不同固结状态下的剪切行为,得出固结状态对土体残余强度的影响很小。
综上,目前针对全风化花岗岩残积土的力学行为有一些前期研究,但针对其长距离剪切特性的研究较少。因此,本文以全风化花岗岩残积土为研究对象,通过一系列环剪试验探讨其长距离剪切过程的力学行为,并分析不同含水率、不同密实度、不同剪切速率以及不同正应力条件的影响规律,以期进一步认识其复杂力学行为,为此类土体上孕育的滑坡灾害防灾减灾提供必要的理论支撑。
1. 试验概况
1.1 试验材料及仪器
试验土样取自浙江省丽水市松阳县象溪镇下麻厂黄金福房后滑坡(图1),边坡案例现场坡高约18 m,坡向194.2°,坡度约32°。该滑坡岩体主要为花岗岩,受气候影响,滑坡表层土体严重风化,根据《岩土工程勘察规范》(GB 50021—2001)中岩体风化程度的划分[30],将岩体分为未风化、微风化、中等风化、强风化、全风化、残积土6个风化等级,其野外鉴定的定性方法包括岩石矿物颜色、结构、破碎程度和坚硬程度等[31]。在本研究中,取样土体主要成分为粗粒石英、强风化长石和高岭土,呈砖红色,强度低,扰动后易溃散,为花岗岩残积土。
1.2 试验设备
试验基于同济大学SRS-150 Bromhead型环剪仪开展,其剪切盒部分示意图如图2所示,包括上剪切盖和下剪切盒。仪器通过对上剪切盖施加荷载实现对剪切槽内试样的固结,并在剪切轴的作用下开始运行剪切。环剪仪的主要参数如表1所示。为了更好地研究剪切带的颗粒材料在剪切变形过程中的力学性质,本文设计了一种新型上剪切盖,如图2c所示。本研究在上剪切盖的下表面均匀布置有10个延伸出来的铁片。这10个铁片从上盖下表面延伸出的长度均为10 mm,厚度均为1.5 mm,宽度均为24.5 mm。如此,在试样剪切过程中剪切齿底部会形成一个随剪切位移不断发展的剪切带,以模拟实际滑坡运动过程中剪切带土体内部的剪切过程。
表 1 同济大学SRS−150型环剪仪主要参数Table 1. Main parameters of the SRS−150 ring shear instrument at Tongji University主要参数 大小 剪切盒内径/mm 100 剪切盒外径/mm 150 最大装填试样高度/mm 31 有效试样面积/cm2 98 剪切速率/(°·min−1) 0.001~360 最大轴向压力/kN 10 峰值扭矩/(N·m) 250 轴向位移/mm 0~50 1.3 试样制备
制备土样时,首先将现场取回的土样粉碎,将土样置入105 °C的恒温烘箱中进行干燥,12 h后取出冷却至室温,干燥过程完成,烘干后过2 mm筛去除大颗粒,并测得烘干后土样级配曲线如图3所示。按照《土工试验方法标准》(GB/T 50123—2019)中制备试样要求,并选取代表性试样进行多组土粒比重试验、密度试验和相对密度试验,得出全风化花岗岩残积土体的物理性质指标,试验结果见表2。同时对烘干冷却后的试样根据不同含水率均匀喷洒不同量的水,搅拌至均匀,并用保鲜膜包裹静止一段时间,确保水分充分混合均匀,具体试样制备流程见图4。
表 2 全风化花岗残积土物理特性Table 2. Physical properties of the tested soil参数 密度/(g·cm−3) 天然含水率/% 比重 最大孔隙比 最小孔隙比 取值 1.066~1.698 10.451 2.644 1.4776 0.5552 1.4 试验方案
含水率会显著影响着土壤的力学性质[28]。本次现场取样的土样自然含水率为10.45%。在本次试验中,含水率分别为0%(干燥)、5%、10%、20%和30%。根据文献资料,全风化花岗岩残积层厚度大概在1~6 m[32 − 33],因此,本研究选择20,50,100,150 kPa的正应力,进行剪切速率为10°/min的环剪试验。剪切速率对滑动带土抗剪强度的影响也较为显著[34 − 36]。因此本研究也考虑了不同剪切速率(10°/min,20°/min,40°/min和80°/min)对土体长距离剪切行为的影响。文章通过在环剪槽内添加不同质量(300,350,400 g)的土体试样,并保证环剪槽内土体试样高度一致,来探究不同相对密实度(14.68%、44.53%和71.83%)对土体抗剪强度的影响。实验工况对应的相对密实度见表3。
表 3 环剪试验工况表Table 3. Ring shear testing conditions试验
编号正应力
/kPa剪切速率
/(°·min−1)剪切位移
/mm含水率
/%相对密实度
/%R1 20 10 130.8 0 71.83 R2 50 10 130.8 0 71.83 R3 100 10 130.8 0 71.83 R4 150 10 130.8 0 71.83 R5 20 10 130.8 5 71.83 R6 20 10 130.8 10 71.83 R7 20 10 130.8 20 71.83 R8 20 10 130.8 30 71.83 R9 50 10 130.8 5 71.83 R10 50 10 130.8 10 71.83 R11 50 10 130.8 20 71.83 R12 50 10 130.8 30 71.83 R13 50 20 130.8 0 71.83 R14 50 40 130.8 0 71.83 R15 50 80 130.8 0 71.83 R16 50 10 130.8 0 14.68 R17 50 10 130.8 0 44.53 本文采用称重−装样−分层压实的方法进行制样。称重时,用精度为0.01 g的电子天平预先称量好指定质量的烘干后的全风化花岗岩试样。然后将称量好的土颗粒倒入并放置在密闭容器中,并充分摇晃使其混合均匀[37]。
待土样称量准备好之后,将样品装入环剪仪的下剪切盒并分层压实。分层压实时,采用分四层压实的方法,即每装填100 g试样,就对该层进行压实。将制备好的试样按每100 g缓慢均匀倒入下剪切盒中,然后用剪切上盖从同一高度落下,对该层进行击实,并重复击实操作20次;如此往复,直至最后一层试样装填压实完毕。制备好的试样高度大概控制在28 mm左右。Sadrekarimi和Olson(2010)在环剪试验中研究发现,土体剪切破坏后,剪切位移仅在宽度为平均粒径(D50)的10~14倍的剪切带内发展[38]。由于本文中设计的上剪切盖,其下表面所延伸出的铁片长度为10 mm,所以剪切带从试样1/3高度位置处逐渐向下发展,所以剪切带的宽度满足平均粒径(D50)的10~14倍的范围,避免了上下界面尺寸效应对试验结果的影响。最后将制备好完成后的试样用螺丝安装固定在试验台上,如图5所示。
2. 试验结果
2.1 含水率对抗剪强度的影响
环剪试验在正应力为20 kPa和50 kPa时不同含水率的应力−剪切位移变化如图6所示,可以看出花岗岩残积土的应力曲线显著受到正应力和含水率变化的影响。图7—8进一步展示了两种正应力下抗剪强度与含水率的关系。结果表明,当含水率处于0~5%,峰值抗剪强度和残余抗剪强度随含水率的增加而降低(图7—8),这与Wang等[27]研究结果一致;当含水率处于5%~10%时,试样的峰值抗剪强度和残余抗剪强度随含水率的增加而上升;当含水率处于10%~30%时,土样的抗剪强度再次随含水率增加而降低,且降低幅度较大。同时,试样的应力-位移曲线在含水率处于10%~20%时,出现较大的波动,含水率在30%时残余剪应力呈现上升趋势,这与低含水率情况有较大区别,总体上随含水率升高试样的抗剪强度出现大幅降低。(需要指出的是,本研究中,不同试验工况的剪切距离是设计为相同的,导致含水率30%时残余强度未得到理论残余强度值,残余剪应力仍处于上升趋势,图7—8中已经做出标记)。从土颗粒间的力学性质上看,在剪切过程中细颗粒之间的结合会产生黏聚力,并且黏聚力大小主要取决于土颗粒之间的微观黏聚力、分子之间的范德华力、水膜连结和胶结作用。在低含水率(0~5%)下,试样固气比大于其固液比,这会导致剪切过程中试样裂缝扩大[39]。同时,由于土样较干燥,导致土体应力分布不均匀,发生不均匀收缩,进一步扩大了先前存在的裂缝[40]。因此,在低含水率下,其黏聚力很低,导致剪应力大幅降低。随着含水率开始增加(10%~20%),土壤孔隙之间的毛细管作用增强,导致黏聚力增加[41]。滑带土壤的黏土矿物在胶结作用下一定程度上增强了土体的强度。导致在含水率的增加过程中,土壤的剪应力呈现上升趋势。然而,随着含水率的不断提高(30%),胶结矿物对土颗粒的黏结作用减弱,土粒−水膜−土粒之间的黏结水膜厚度增加。土颗粒之间的黏结水膜最终由持续变得间歇性,从而大幅降低了黏聚力,导致抗剪强度大幅下降[42]。
2.2 正应力对抗剪强度的影响
试验中我们进行了干燥(含水率0%)条件下,土样在不同正应力和相对密实度情况下的环剪试验。结果表明,土体的剪切强度与正应力呈较好的相关性。如图9所示可以看到,正应力越大,土体的剪应力也越大,滑带土的抗剪强度受正应力的影响也更显著[43]。在干燥且剪切速率不变的情况下,如图10所示,试验结果表明,峰值抗剪强度和残余抗剪强度会随着正应力的增加而增加。
在本试验中,试样明显表现出应变软化,残余抗剪强度与峰值抗剪强度的差值与正应力呈正相关。如图10所示,在20~150 kPa的正应力范围内,差异分别为6.34,15.65,18.09,20.87 kPa。这表明试样的上覆压力是影响土壤峰值抗剪强度的重要因素,上覆压力较大的试样具有更大的密实度和更大的剪缩量。这一现象在图12、13不同密实度下土体的应力−剪切位移曲线和抗剪强度曲线中也得到很好的验证。结果显示,当土样相对密度增大时土体的峰值抗剪强度与残余抗剪强度也随之增大,其峰值抗剪强度与残余抗剪强度的差值分别为7.13,7.36,15.65 kPa,并且如图14所示,土体的剪缩量也随之减少,在正应力和相对密实度增加的情况下,土颗粒的黏结、摩擦和互锁都得到了加强。因此,土体试样的峰值抗剪强度更大。
2.3 剪切速率对抗剪强度的影响
为了探究剪切速率对花岗岩残积土力学性质的影响,试验中我们进行了干燥(含水率0%)条件下,土样在不同剪切速率下的环剪试验。在试验中我们将剪切速率设定为10,20,40,80°/min。从图15—16可以看出,在其他条件不变时,随着剪切速率的增加,无论是土体的峰值抗剪强度还是残余抗剪强度,总体均呈现下降趋势,且对峰值抗剪强度的影响要大于残余抗剪强度。这是由于当剪切速度较慢时,颗粒有充足的时间进行自主排列,能使颗粒之间的摩擦效应发挥作用,而在高剪切速率的影响下,颗粒之间更容易发生定向排列,抵抗剪切的能力减弱,更容易发生剪切破坏。图17整体上看试样剪缩趋势无明显规律,但通过分析剪胀最高点到剪缩最低点处的相对位移,结果表明除剪切速度80°/min时,试样的相对剪缩效果随剪切速度升高而增大。同时试验还发现,剪切速率对土体的表观黏度也有显著影响,如图18所示,剪切速率与表观黏度呈现明显的负相关性,且剪切速度为10°/min时要明显高于其他剪切速度时试样的表观黏度。
3. 讨 论
中国东南沿海地区广泛分布花岗岩地层,由于区域气候特点,时常出现短时强降雨、极端暴雨,引起土体含水率短时突变,导致花岗岩地区频繁发生群发性滑坡灾害。滑坡的变形破坏与花岗岩残积土的非饱和-饱和过程联系紧密。含水率(w)是影响残余抗剪强度的重要因素[28, 39, 43]。Wang等[27]研究了不同正应力和剪切速率下,含水率在(6%、9%、12%)时的滑带土的残余抗剪强度变化。研究认为,残余抗剪强度随着含水率的增加而略有下降,无论正应力和剪切速率如何变化,含水率的增加都会有效地降低残余应力。黄淙葆等[44]基于贵州某公路边坡土体材料的试验结果发现,当含水量较高时,残余强度可能展示出较为复杂的变化特征,如先增加,如减小等,难以达到相对平稳值。因此,含水量对土体残余强度的影响值得进一步关注。试验结果表明,花岗岩残积土的抗剪强度随含水率的增加呈现先下降(含水率0~5%),后上升(含水率5%~10%)在大幅下降(含水率10%~30%)的趋势。随着花岗岩残积土含水率接近饱和,当含水率为30%时,土体在剪切的作用下,土的应力-剪切位移曲线表现为应变硬化特征,且正应力为50 kPa时试样的应变硬化程度要明显高于正应力为20 kPa时,这可能与较高的正应力所引起孔隙水压的变化有关。高含水率下土体出现应变硬化现象是多种机制共同作用的结果,包括孔隙水压力的变化[45]、颗粒间摩擦力的增加[46]、土体结构的重新排列以及局部排水效应[44, 47]等。在本试验中,一方面,含水率变化影响了土体内部结构,改变了土体内部的水膜联结作用和水膜润滑作用,高含水率时,土粒间的结合水膜增厚,胶结力仍然居高不下,使得颗粒重新定向排列,颗粒间的咬合度进一步增强,促使应变硬化现象发生。此外,当含水率过高时,土壤中会出现自由水,在不断剪切的作用下使得孔隙水压力不能及时消散,导致孔隙水向剪切面迁移。由图19也可以看出,剪切面上的含水率明显高于其他位置土体的含水率。一方面,这使得附着在土颗粒上的水膜可以随土颗粒移动,起到润滑作用;另一方面,土颗粒又在不断聚集,从而使土体密实度不断增加,残余抗剪强度不断上升,出现应变硬化。
综合不同含水率条件下剪应力变化趋势可以看出,试样的剪应力变化综合受到正应力与含水率的影响,在不同条件下他们的影响效果各占优势。然而,这不仅仅是含水率和正应力的贡献;对于正常的再固结土体,不同正应力下,不同的含水率意味着不同的密实度。此外,在剪切速率和正应力条件不变时,试验结果也表明当含水率大于天然含水率时,土体的峰值强度和残余强度均随含水率的升高而下降,证明了含水率的升高会降低土体的力学性质,而这一现象恰恰发生在降雨后。这也解释了为什么降雨是导致浅层滑坡滑移的关键因素。
研究还发现,相比于黄土和其他土体,本研究采用的花岗岩残积土在不同含水率下土体的力学性质有较大差异,出现的应变软化和应变硬化对应的含水率区间也有较大差别。如对分散性土进行环剪试验时发现当含水率为5%~14%、正应力为50 kPa时出现应变软化特征,此后含水率从17%增长至24%,试样均表现出应变硬化的特性[46];在黄土的环剪试验中,含水率8%~24%、正应力100~300 kPa,除含水量为16%的土样在300 kPa应力作用下表现为应变软化外,土的应力-应变曲线均表现为应变硬化特征[28]。由此可以看出通过分析花岗岩残积土特有的土体强度衰减规律和临界含水率阈值,在滑坡排水防治中实现对含水率的精准控制有着重要的现实意义。工程实践中,在我国东南沿海地区应加强对人类活动区,特别是山体高切坡地段的排水设施建设。在强降雨季节,应加强排水,以降低滑带岩土体的含水率;在持续性降雨季节,需定期监测坡体岩土体水量变,通过科学的工程设计和动态监测,有效降低坡体含水率,提高稳定性,最大限度地减少滑坡灾害风险。
剪切带上覆土层厚度的变化也会显著影响坡体滑动过程中剪切带土力学性质的变化。上覆土层较厚会使土体颗粒之间变得更加紧凑,导致滑动过程中颗粒间相互作用更加强烈,颗粒之间相互挤压,碰撞,导致摩擦力也随之增加。这一点在图11中可以得到很好的印证,从图中可以看出,土体上覆荷载越大,其剪胀就越小,剪缩也越大。剪切过程中的力更多地来自大颗粒之间的摩擦力。也说明上覆土层越厚,滑坡的抗剪强度越大,越不易发生滑动[48]。随着土体试样的剪切破坏,在上覆压力的作用下导致固结的颗粒发生滚动和重排,改变了土体的强度,颗粒之间的黏结减弱,导致颗粒被压实和挤压,强度降低[7]。此时土样的抗剪强度主要由土颗粒之间的摩擦主导[49]。另一方面,在正应力较大的条件下,土体颗粒也会发生颗粒破碎现象,导致细颗粒含量增高[50 − 51]。在颗粒破碎和重排作用下在剪切带形成由细颗粒组成的边界层,产生润滑效应[52],显著增加了颗粒的流动迁移率。剪切带破碎颗粒的持续产生和颗粒重排,特别是细颗粒的不断增加,也被认为是改变颗粒系统的流变特性,促使滑坡以较高速率滑动的关键因素[53]。
此外,研究也表明较高的剪切速率可以显著降低土颗粒流动时的表观黏度,从而提高土体的流动性。Davies[54]研究了大型岩石雪崩的流态化机制,指出在高剪切速率下,颗粒间会发生高脉冲接触应力,从而降低基底摩擦系数,促进滑坡的长距离运动。因此,本试验结果表明,全风化花岗岩残积土也具有类似的剪切稀化特性,其长距离流动过程的动力致灾效益不可忽视。因此针对距离坡体较近的下游居民区,在滑坡防治中仍需考虑其长距离流动过程的动力致灾效应,综合采取“源头控制-路径拦截-末端防护”的治理策略,结合监测预警和应急管理,形成完整的防灾减灾体系,避免发生滑坡长距离流动引发的次生灾害,保障下游居民安全。
4. 结 论
(1)全风化花岗岩残积土的力学性质与土体含水率密切相关,土体的峰值强度和残余强度均随含水率的升高而下降,在高含水率(30%)时出现应变硬化现象。
(2)全风化花岗岩残积土的峰值抗剪强度和残余抗剪强度与正应力总体成正比关系,但峰值强度增长更为明显。较大的法向应力导致残余强度的增量更小。
(3)全风化花岗岩残积土具有剪切稀化特征。剪切速率越大,土体的峰值抗剪强度和残余抗剪强度越小,表观黏度也越小。
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表 1 同济大学SRS−150型环剪仪主要参数
Table 1 Main parameters of the SRS−150 ring shear instrument at Tongji University
主要参数 大小 剪切盒内径/mm 100 剪切盒外径/mm 150 最大装填试样高度/mm 31 有效试样面积/cm2 98 剪切速率/(°·min−1) 0.001~360 最大轴向压力/kN 10 峰值扭矩/(N·m) 250 轴向位移/mm 0~50 表 2 全风化花岗残积土物理特性
Table 2 Physical properties of the tested soil
参数 密度/(g·cm−3) 天然含水率/% 比重 最大孔隙比 最小孔隙比 取值 1.066~1.698 10.451 2.644 1.4776 0.5552 表 3 环剪试验工况表
Table 3 Ring shear testing conditions
试验
编号正应力
/kPa剪切速率
/(°·min−1)剪切位移
/mm含水率
/%相对密实度
/%R1 20 10 130.8 0 71.83 R2 50 10 130.8 0 71.83 R3 100 10 130.8 0 71.83 R4 150 10 130.8 0 71.83 R5 20 10 130.8 5 71.83 R6 20 10 130.8 10 71.83 R7 20 10 130.8 20 71.83 R8 20 10 130.8 30 71.83 R9 50 10 130.8 5 71.83 R10 50 10 130.8 10 71.83 R11 50 10 130.8 20 71.83 R12 50 10 130.8 30 71.83 R13 50 20 130.8 0 71.83 R14 50 40 130.8 0 71.83 R15 50 80 130.8 0 71.83 R16 50 10 130.8 0 14.68 R17 50 10 130.8 0 44.53 -
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