(1. Hunan Provincial Key Laboratory of Geotechnical Engineering Stability Control and Health Monitoring，Hunan University of Science and Technology，Xiangtan，Hunan 411201，China；2. Fujian Research Center for Tunneling and Urban
Underground Space Engineering，Huaqiao University，Xiamen，Fujian 361021，China；3. China Railway
No.5 Engineering Group Co.，Ltd.，Changsha，Hunan 410021，China；4. College of Civil
Engineering，Hunan University，Changsha，Hunan 410082，China)
Abstract：The geographical distribution of discontinuous graded soil-rock mixtures is extensive，and these materials are commonly used as backfill materials in subgrade and slope engineering. The discontinuous grading effect on their shear mechanical properties is a critical factor influencing compaction quality control. This study proposes a discontinuity index that effectively quantifies the discontinuous grading characteristics of soil-rock mixtures. Large-scale triaxial standard specimens of soil-rock mixtures with different discontinuity indices were prepared，and triaxial shear tests were conducted using the DJSZ–150 large-scale triaxial testing apparatus. The influence of and confining pressure on the strength and deformation characteristics of soil-rock mixtures was analyzed. Subsequently，intrinsic relationships between the parameters of the composite power-exponential model and the deviatoric stress strength， and were investigated，leading to the development of the CPE model，which accounts for the effects of varying interrupted grain fractions and stress states. Finally，the impact of changes in discontinuous particle size fractions on the mesoscopic structural characteristics of soil-rock mixtures was explored，elucidating the discontinuous gradation effect on their shear mechanical properties. The results indicate that under triaxial compression，discontinuous graded soil-rock mixtures typically exhibit strain hardening characteristics. The deviatoric stress strength increases with the increase in ，while the internal friction angle initially increases and then decreases with the increase in . In contrast，the cohesion exhibits an opposite trend. The parameters k，b，and n showing linear relationships with the . Both k and n show a linear relationship with the ，while b follows a quadratic function relationship with . The improved CPE model not only accurately predicts the strength and deformation characteristics of soil-rock mixtures，but also effectively reflects the influence of discontinuous grading features and stress state on their deformational mechanical behavior of soil-rock mixtures. Different discontinuous particle groups constitute distinct mesostructural characteristics of soil-rock mixtures. Under axial compression loading，an increase in the content of the largest particle group enhances the overall deformational mechanical properties of the soil-rock mixture. However，excessive amounts of large particles can increase the voids between coarse particles，leading to an initial increase in deviatoric stress strength followed by a decrease.
[1] 秦 雯，沙爱民，胡 倩. 混合料贮料仓离析现象试验研究[J]. 岩土力学，2009，30(增1)：99–102.(QIN Wen，SHA Aimin，HU Qian. Experimental study on segregation phenomenon of mixture storage bin of mixed materials[J]. Rock and Soil Mechanics，2009，30(Supp.1)：99–102.(in Chinese))
[2] XU W J，ZHANG H Y. Meso and macroscale mechanical behaviors of soil-rock mixtures[J]. Acta Geotechnica，2022，17(9)：3 765–3 782.
[3] 金 磊，曾亚武，张 森. 块石含量及形状对胶结土石混合体力学性能影响的大型三轴试验[J]. 岩土力学，2017，38(1)：141–149.(JIN Lei，ZENG Yawu，ZHANG Sen. Large-scale triaxial test on the effect of rock block content and shape on the mechanical properties of cemented soil-rock mixture[J]. Rock and Soil Mechanics，2017，38(1)：141–149.(in Chinese))
[4] WEI H Z，XU W J，XU X F，et al. Mechanical properties of strongly weathered rock-soil mixtures with different rock block contents[J]. International Journal of Geomechanics，2018，18(5)：04018026.
[5] YAO Y S，LI J，NI J J，et al. Effects of gravel content and shape on shear behaviour of soil-rock mixture：Experiment and DEM modelling[J]. Computers and Geotechnics，2022，141：104476.
[6] 张俊云，张 乐，高福洲，等. 干湿循环下红层土石混合料强度及变形特性的试验研究[J]. 西南交通大学学报，2023，58(6)：1 394–1 404.(ZHANG Junyun，ZHANG Le，GAO Fuzhou，et al. Experimental study on the strength and deformation characteristics of red-bed soil-rock mixtures under dry-wet cycling[J]. Journal of Southwest Jiaotong University，2023，58(6)：1 394–1 404.(in Chinese))
[7] 王江营，曹文贵，张 超，等. 基于正交设计的复杂环境下土石混填体大型直剪试验研究[J]. 岩土工程学报，2013，35(10)：1 849–1 855.(WANG Jiangying，CAO Wengui，ZHANG Chao，et al. Large-scale direct shear test study of soil-rock mixture fill under complex environmental conditions based on orthogonal design[J]. Chinese Journal of Geotechnical Engineering，2013，35(10)：1 849–1 855.(in Chinese))
[8] XU W J，XU Q，HU R L. Study on the shear strength of soil-rock mixture by large scale direct shear test[J]. International Journal of Rock Mechanics and Mining Sciences，2011，48(8)：1 235–1 247.
[9] COLI N，BERRY P，BOLDINI D. In situ non-conventional shear tests for the mechanical characterization of a bimrock(BimTest)[J]. International Journal of Rock Mechanics and Mining Sciences，2011，48(1)：95–102.
[10] ZHANG Y，LU J Y，HAN W，et al. Effects of moisture and stone content on the shear strength characteristics of soil-rock mixture[J]. Materials，2023，16(2)：567.
[11] 刘飞禹，孔剑捷，姚嘉敏. 含石量和压实度对格栅–土石混合体界面剪切特性的影响[J]. 岩土工程学报，2023，45(5)：903–911.(LIU Feiyu，KONG Jianjie，YAO Jiamin. Influence of rock content and compaction degree on the interface shear characteristics of geogrid-soil-rock mixture[J]. Chinese Journal of Geotechnical Engineering，2023，45(5)：903–911.(in Chinese))
[12] 雷晓丹，杨忠平，张晓景，等. 土石混合料剪切特性及块石破碎特征[J]. 岩土力学，2018，39(3)：899–908.(LEI Xiaodan，YANG Zhongping，ZHANG Xiaojing，et al. Shear characteristics and rock fragmentation features of soil-rock mixture[J]. Rock and Soil Mechanics，2018，39(3)：899–908.(in Chinese))
[13] LE V T，MAROT D，ROCHIM A，et al. Suffusion susceptibility investigation by energy based method and statistical analysis[J]. Canadian Geotechnical Journal，2018，55(1)：57–68.
[14] 梁 越，龚胜勇，杨咏梅，等. 间断级配散粒土侵蚀过程及强度演变机制研究[J]. 岩土工程学报，2024，46(3)：632–639.(LIANG Yue，GONG Shengyong，YANG Yongmei，et al. Study on the erosion process and strength evolution mechanism of intermittent graded granular soil[J]. Chinese Journal of Geotechnical Engineering，2024，46(3)：632–639.(in Chinese))
[15] 张天军，王小军，庞明坤，等. 考虑间断级配的破碎矸石压实和再破碎研究[J]. 中南大学学报：自然科学版，2023，54(1)：314–326. (ZHANG Tianjun，WANG Xiaojun，PANG Mingkun，et al. Study on compaction and re-crushing of crushed waste rock considering discontinuous grading[J]. Journal of Central South University：Natural Science，2023，54(1)：314–326.(in Chinese))
[16] 郭万里，朱俊高，钱 彬，等. 粗粒土的颗粒破碎演化模型及其试验验证[J]. 岩土力学，2019，40(3)：1 023–1 029.(GUO Wanli，ZHU Jungao，QIAN Bin，et al. Evolution model of particle breakage of coarse-grained soil and its experimental verification[J]. Rock and Soil Mechanics，2019，40(3)：1 023–1 029.(in Chinese))
[17] 赵飞翔，迟世春，米晓飞. 基于颗粒破碎特性的堆石材料级配演化模型[J]. 岩土工程学报，2019，41(9)：1 707–1 714.(ZHAO Feixiang，CHI Shichun，MI Xiaofei. Evolution model of rockfill material grading based on particle crushing characteristics[J]. Chinese Journal of Geotechnical Engineering，2019，41(9)：1 707–1 714.(in Chinese))
[18] 于际都，刘斯宏，王 涛，等. 间断级配粗粒土压实特性试验研究[J]. 岩土工程学报，2019，41(11)：2 142–2 148.(YU Jidu， LIU Sihong，WANG Tao，et al. Experimental study on compaction properties of discontinuous graded coarse-grained soil[J]. Chinese Journal of Geotechnical Engineering，2019，41(11)：2 142–2 148.(in Chinese))
[19] HAO S P，PABST T. Mechanical characterization of coarse-grained waste rocks using large-scale triaxial tests and neuroevolution of augmenting topologies[J]. Journal of Geotechnical and Geoenvironmental Engineering，2023，149(6)：04023039.
[20] 李广信. 土力学[M]. 北京：中国水利水电出版社，2018：9–10.(LI Guangxin. Soil mechanics[M]. Beijing：China Water and Power Press，2018：9–10.(in Chinese))
[21] MEDLEY E W. Observations on tortuous failure surfaces in Bimrocks[J]. Geomechanics and Tunnelling，2004，22(5)：35–43.
[22] 中华人民共和国行业标准编写组. JTG/E40—2007 公路土工试验规程[S]. 北京：人民交通出版社，2007.(The Professional Standard Compilation Groups of People?s Republic of China. JTG/E40—2007 Test methods of soils for highway engineering[S]. Beijing：China Communications Press，2007.(in Chinese))
[23] 王丽琴，鹿忠刚，邵生俊. 岩土体复合幂–指数非线性模型[J]. 岩石力学与工程学报，2017，36(5)：1 269–1 278.(WANG Liqin，LU Zhonggang，SHAO Shengjun. Composite power-exponential nonlinear model for rock and soil mass[J]. Chinese Journal of Rock Mechanics and Engineering，2017，36(5)：1 269–1 278.(in Chinese))
2025, Vol. 44 
