The characteristics of residual soils are very different from those of sedimentary soils.Although the strength characteristics of sedimentary soils have been studied extensively,the shear strength characteristics of g...The characteristics of residual soils are very different from those of sedimentary soils.Although the strength characteristics of sedimentary soils have been studied extensively,the shear strength characteristics of granitic residual soils(GRS)subjected to the weathering of parent rocks have rarely been investigated.In this study,the shear strength characteristics of GRS in the Taishan area of southeast China(TSGRS)were studied by field and laboratory tests.The field tests consisted of a cone penetration test(CPT),borehole shear test(BST),self-boring pressuremeter test(SBPT),and seismic dilatometer Marchetti test(SDMT).The shortcomings of laboratory testing are obvious,with potential disturbances arising through the sampling,transportation,and preparation of soil samples.Due to the special structure of GRS samples and the ease of disturbance,the results obtained from laboratory tests were generally lower than those obtained from situ tests.The CPT and scanning electron microscopy(SEM)results indicated significant weathering and crustal hardening in the shallow TSGRS.This resulted in significant differences in the strength and strength parameters of shallow soil obtained by the BST.Based on the SDMT and SBPT results,a comprehensive evaluation method of shear strength for TSGRS was proposed.The SBPT was suitable for evaluating the strength of shallow GRS.The material index(ID)and horizontal stress index(KD)values obtained by the SDMT satisfied the empirical relationship proposed by Marchetti based on the ID index,and were therefore considered suitable for the evaluation of the shear strength of deep GRS.展开更多
Xiangjiaba hydropowcr station is one of the complicated geological conditions of its dam foundation, parameters of rock masses are very important issues. To cascade power stations on the Jinsha River, China. Due to th...Xiangjiaba hydropowcr station is one of the complicated geological conditions of its dam foundation, parameters of rock masses are very important issues. To cascade power stations on the Jinsha River, China. Due to the evaluating the rock mass quality and determining the mechanical address these issues, several groups of rock borehole shear tests （RBSTs） were conducted on the black mudstone in the dam foundation of Xiangjiaba hydropower station in the second construction phase. Forty three groups of shear strengths of black mudstone samples were obtained from RBSTs, and the shear strength parameters （c and f） were calculated using the least squares method. In addition, the limitations and merits of RBST employed in the Xiangjiaba hydropower station were discussed. Test results indicate that the shear strength parameters obtained from RBST have a good correlation with the results from sotmd wave test in borehole. It is believed that RBST has a good adaptability and applicability in geotechnical engineering.展开更多
Based on the principle formula for the four-component strainmeters, we can directly obtain the specific plane strain, shear strain and azimuthal angle of the principal strain, and the maximum and minimum principal str...Based on the principle formula for the four-component strainmeters, we can directly obtain the specific plane strain, shear strain and azimuthal angle of the principal strain, and the maximum and minimum principal strains calculated afterwards are the indirect result. The problems of practicality of the sensitivity coefficients A and B of plane strain and shear strain are then discussed. Based on this idea, we analyzed the observation data of several four-component borehole strainmeters near the epicenter of the Yiliang M_S5.7 earthquake in 2012 and the Ludian M_S6.5 earthquake in 2014 in the Zhaotong area, Yunnan Province. The results show that the analysis based on the perspective of plane strain and shear strain has an obviously better effect than that based on the component readings, and can directly peel off the respective abnormality of the plane strain and shear strain. In addition, the correlation coefficient curves between measured data of two plane strains show significant anomalies which often occur several days before and during the earthquake.展开更多
针对膨胀土堑坡防护工程中不同的施工工序和降水入渗诱发灾害频发现象,基于原位孔内剪切试验,通过施加不同法向应力水平,以及成孔后注水浸泡等工况下的现场剪切试验,获得南阳某堑坡膨胀土强度特性随荷载施加方式与浸水条件的变化规律。...针对膨胀土堑坡防护工程中不同的施工工序和降水入渗诱发灾害频发现象,基于原位孔内剪切试验,通过施加不同法向应力水平,以及成孔后注水浸泡等工况下的现场剪切试验,获得南阳某堑坡膨胀土强度特性随荷载施加方式与浸水条件的变化规律。结果表明:膨胀土孔内剪切试验所得的剪应力-剪切位移曲线总体上呈现弱硬化变形特征;浸水对抗剪强度影响很大,最大降幅达56.9%,主要表现为黏聚力的降低,最大值达18.1 k Pa。预加载荷对浸水软化效应具有一定抑制作用,但当预加载荷超过某一应力水平时,难以发挥更大的抑制效果。黏聚力与预加载荷呈线性正相关;内摩擦角与预加载荷呈线性负相关,但降幅甚微。在实际工程中,膨胀土边坡稳定性分析应考虑降雨入渗对强度参数的影响,同时充分利用抗剪强度参数和预加载荷的线性关系,可根据工程要求达到的安全系数反推出所需的预加载荷大小,从而指导实际工程施工。该研究可为膨胀土工程场地评价、参数选取与灾害评价提供技术依据和参考。展开更多
安县大光包滑坡是汶川地震触发的最大规模滑坡,滑坡南侧暴露长约1.8 km顺层滑带,其岩体高度碎裂化,引起广泛关注。为准确评价滑带碎裂岩体的强度参数,笔者在前人研究的基础上开展了细致的野外调查工作,采用法国Phicometre岩土两用原位...安县大光包滑坡是汶川地震触发的最大规模滑坡,滑坡南侧暴露长约1.8 km顺层滑带,其岩体高度碎裂化,引起广泛关注。为准确评价滑带碎裂岩体的强度参数,笔者在前人研究的基础上开展了细致的野外调查工作,采用法国Phicometre岩土两用原位钻孔剪切试验仪对大光包滑坡滑带碎裂岩体进行了原位剪切试验。将试验结果与Hoek–Brown岩体强度准则估值和基于工程地质类比法的力学参数建议值进行了对比分析。基于以上研究,提出了大光包滑坡南侧顺层滑带碎裂岩体力学参数建议值:内聚力为245~480 k Pa,内摩擦角为25.0°~26.5°。展开更多
基金the funding support from the National Natural Science Foundation of China(Grant No.51709290)the Key Scientific Research Project of colleges and universities in Henan Province-Special Project of Basic Research(Grant No.20zx009)the Key Research Projects of Higher Education Institutions in Henan Province(Grant No.22A580008).
文摘The characteristics of residual soils are very different from those of sedimentary soils.Although the strength characteristics of sedimentary soils have been studied extensively,the shear strength characteristics of granitic residual soils(GRS)subjected to the weathering of parent rocks have rarely been investigated.In this study,the shear strength characteristics of GRS in the Taishan area of southeast China(TSGRS)were studied by field and laboratory tests.The field tests consisted of a cone penetration test(CPT),borehole shear test(BST),self-boring pressuremeter test(SBPT),and seismic dilatometer Marchetti test(SDMT).The shortcomings of laboratory testing are obvious,with potential disturbances arising through the sampling,transportation,and preparation of soil samples.Due to the special structure of GRS samples and the ease of disturbance,the results obtained from laboratory tests were generally lower than those obtained from situ tests.The CPT and scanning electron microscopy(SEM)results indicated significant weathering and crustal hardening in the shallow TSGRS.This resulted in significant differences in the strength and strength parameters of shallow soil obtained by the BST.Based on the SDMT and SBPT results,a comprehensive evaluation method of shear strength for TSGRS was proposed.The SBPT was suitable for evaluating the strength of shallow GRS.The material index(ID)and horizontal stress index(KD)values obtained by the SDMT satisfied the empirical relationship proposed by Marchetti based on the ID index,and were therefore considered suitable for the evaluation of the shear strength of deep GRS.
基金Supported by the National Basic Research Program of China(973 Program)(2011CB013502)the Youth Special Foundation of IWHR(YJ1106)
文摘Xiangjiaba hydropowcr station is one of the complicated geological conditions of its dam foundation, parameters of rock masses are very important issues. To cascade power stations on the Jinsha River, China. Due to the evaluating the rock mass quality and determining the mechanical address these issues, several groups of rock borehole shear tests （RBSTs） were conducted on the black mudstone in the dam foundation of Xiangjiaba hydropower station in the second construction phase. Forty three groups of shear strengths of black mudstone samples were obtained from RBSTs, and the shear strength parameters （c and f） were calculated using the least squares method. In addition, the limitations and merits of RBST employed in the Xiangjiaba hydropower station were discussed. Test results indicate that the shear strength parameters obtained from RBST have a good correlation with the results from sotmd wave test in borehole. It is believed that RBST has a good adaptability and applicability in geotechnical engineering.
基金sponsored by the Central Level Scientific Research Institutes of Basic R&D Special Fund Business of the Institute of Crustal Dynamics,CEA(ZDJ2017-25)
文摘Based on the principle formula for the four-component strainmeters, we can directly obtain the specific plane strain, shear strain and azimuthal angle of the principal strain, and the maximum and minimum principal strains calculated afterwards are the indirect result. The problems of practicality of the sensitivity coefficients A and B of plane strain and shear strain are then discussed. Based on this idea, we analyzed the observation data of several four-component borehole strainmeters near the epicenter of the Yiliang M_S5.7 earthquake in 2012 and the Ludian M_S6.5 earthquake in 2014 in the Zhaotong area, Yunnan Province. The results show that the analysis based on the perspective of plane strain and shear strain has an obviously better effect than that based on the component readings, and can directly peel off the respective abnormality of the plane strain and shear strain. In addition, the correlation coefficient curves between measured data of two plane strains show significant anomalies which often occur several days before and during the earthquake.
基金国家自然科学基金重点项目(No.41430634)supported by the Key Program of National Nature Science Foundation of China(41430634)
文摘针对膨胀土堑坡防护工程中不同的施工工序和降水入渗诱发灾害频发现象,基于原位孔内剪切试验,通过施加不同法向应力水平,以及成孔后注水浸泡等工况下的现场剪切试验,获得南阳某堑坡膨胀土强度特性随荷载施加方式与浸水条件的变化规律。结果表明:膨胀土孔内剪切试验所得的剪应力-剪切位移曲线总体上呈现弱硬化变形特征;浸水对抗剪强度影响很大,最大降幅达56.9%,主要表现为黏聚力的降低,最大值达18.1 k Pa。预加载荷对浸水软化效应具有一定抑制作用,但当预加载荷超过某一应力水平时,难以发挥更大的抑制效果。黏聚力与预加载荷呈线性正相关;内摩擦角与预加载荷呈线性负相关,但降幅甚微。在实际工程中,膨胀土边坡稳定性分析应考虑降雨入渗对强度参数的影响,同时充分利用抗剪强度参数和预加载荷的线性关系,可根据工程要求达到的安全系数反推出所需的预加载荷大小,从而指导实际工程施工。该研究可为膨胀土工程场地评价、参数选取与灾害评价提供技术依据和参考。
文摘安县大光包滑坡是汶川地震触发的最大规模滑坡,滑坡南侧暴露长约1.8 km顺层滑带,其岩体高度碎裂化,引起广泛关注。为准确评价滑带碎裂岩体的强度参数,笔者在前人研究的基础上开展了细致的野外调查工作,采用法国Phicometre岩土两用原位钻孔剪切试验仪对大光包滑坡滑带碎裂岩体进行了原位剪切试验。将试验结果与Hoek–Brown岩体强度准则估值和基于工程地质类比法的力学参数建议值进行了对比分析。基于以上研究,提出了大光包滑坡南侧顺层滑带碎裂岩体力学参数建议值:内聚力为245~480 k Pa,内摩擦角为25.0°~26.5°。
