冻融岩石抗拉强度是寒区岩土工程结构稳定性评价的关键力学指标。本文以砂岩为研究对象，开展冻融循环作用下砂岩抗拉性能劣化机理研究，对于寒区岩土工程稳定性评判具有理论意义和实践意义。 完成了两种粒径砂岩不同冻融循环次数巴西劈裂声发射实时试验。随着冻融循环次数的增加，两种粒径砂岩抗拉强度均减小；细粒砂岩破坏模式为中央劈裂，粗粒砂岩为非中央劈裂；冻融循环作用下砂岩巴西劈裂损伤具有连续演进的特征，关键时刻损伤发育速度有突变。冻融循环为5次时损伤速度增大，声发射能量与事件频率出现突增。随冻融循环次数增加，砂岩破坏呈现由脆性破坏向延性破坏转变的趋势。高能声发射事件多发于损伤快速扩展期，可作为损伤传导和加剧的重要参照。振铃计数和累计能量同步大幅度激增至更高数量级是冻融砂岩破坏失稳时间域的前兆信息。随冻融循环次数增加，b值先降低后增大，可反映出砂岩破坏模式，由内部大裂隙破坏转变为持续小裂隙破坏。 完成了两种粒径砂岩在不同冻融循环次数下的细观损伤观测试验，实现了冻融岩石CT图像的伪彩色增强技术，伪彩色增强技术提高了CT图像的视觉分辨率。伪彩色增强图像中的细观结构和损伤信息，表明冻融循环作用下砂岩损伤扩展始于初始损伤。在裂缝形成和扩展阶段之后，冻融损伤逐渐增大，岩石的有效承载面积不断减小。 完成了两种粒径砂岩在不同冻融循环次数和不同加载速率下及三种粒径砂岩在0次冻融循环下的巴西劈裂破坏过程数值模拟。随着冻融循环次数的增加，抗拉强度呈现下降趋势；随着粒径的增加，抗拉强度呈现下降趋势；随着加载速率的增加，抗拉强度呈现增大趋势。细粒砂岩经历20次冻融循环后，加载速率效应不再明显，随加载速率增加抗拉强度变化很小。声发射事件初始位置与岩石裂纹扩展的初始位置相同，岩石声发射事件开始出现时，并没有明显的裂隙产生，裂纹扩展方向与声发射扩展方向相同，并且基本在同一路径上。

The tensile strength of freeze-thaw rock is a key mechanical index for the stability evaluation of geotechnical engineering structures in cold regions. Taking sandstone as the research object, this paper studies the deterioration mechanism of tensile properties of sandstone under freeze-thaw cycles, which has theoretical and practical significance for the stability evaluation of geotechnical engineering in cold regions.

The Brazilian splitting acoustic emission real-time test of two kinds of sandstone with different freeze-thaw cycles was completed. With the increase of freeze-thaw cycles, the tensile strength of the two sizes of sandstone decreases; The failure mode of fine-grained sandstone is central splitting, and that of coarse-grained sandstone is non central splitting; Under the action of freeze-thaw cycles, the Brazilian fracturing damage of sandstone has the characteristics of continuous evolution, and the damage development rate has a sudden change at the critical moment. When the freeze-thaw cycle is 5 times, the damage velocity increases, and the AE energy and event frequency increase abruptly. With the increase of freeze-thaw cycles, the failure of sandstone changes from brittle failure to ductile failure. High energy acoustic emission events often occur in the rapid expansion period of damage, which can be used as an important reference for damage conduction and aggravation. The ringing count and cumulative energy increase to a higher order simultaneously, which is the precursor information of the failure time domain of freeze-thaw sandstone. With the increase of freeze-thaw cycles, b value first decreases and then increases, which can reflect the failure mode of sandstone, from internal large fracture failure to continuous small fracture failure.

The microscopic damage observation experiments of two kinds of sandstone under different freeze-thaw cycles are completed, and the pseudo color enhancement technology of CT image of freeze-thaw rock is realized. The pseudo color enhancement technology improves the visual resolution of CT image. The micro structure and damage information in the pseudo color enhanced image indicate that the damage propagation of sandstone under freeze-thaw cycle starts from the initial damage. After the crack formation and propagation stage, the freeze-thaw damage increases gradually, and the effective bearing area of rock decreases.

The numerical simulation of Brazilian splitting failure process of two kinds of grain size sandstone under different freeze-thaw cycles and loading rates and three kinds of grain size sandstone under zero freeze-thaw cycles was completed. With the increase of freeze-thaw cycles, the tensile strength decreased; The tensile strength decreases with the increase of particle size; With the increase of loading rate, the tensile strength increases. After 20 freeze-thaw cycles, the effect of loading rate is no longer obvious, and the tensile strength changes little with the increase of loading rate. The initial position of acoustic emission event is the same as that of rock crack propagation. When the acoustic emission event begins to appear, there is no obvious crack, and the crack propagation direction is the same as that of acoustic emission, and it is basically in the same path.

[1] 赖远明,张明义,李双洋.寒区工程理论与应用[M].北京:科学出版社,2009.

[2] 马巍,牛富俊,穆彦虎.青藏高原重大冻土工程的基础研究[J].地球科学进展,2012,27

(11):1185-1191.

[3] Jie-lin LI, Ke-ping ZHOU, Wei-jie LIU, et al. NMR research on deterioration characteristics of microscopic structure of sandstones in freeze−thaw cycles[J].ELSEVIER, 2016,2997-3003.

[4] Gholamreza Khanlari & Reza Zarei Sahamieh &Yasin Abdilor. The effect of freeze-thaw cycles on physical and mechanical properties of Upper Red Formation sa-ndstones, central part of Iran[J]. Arab J Geosci ,2015, 8:5991-6001.

[5] Jihwan Park ,Chang-Uk Hyun , Hyeong-Dong Park. Changes in microstructure and physical properties of rocks caused by artificial freeze–thaw action[J]. Bull Eng Geol Environ,2015, 74:555-565.

[6] Javier M M, David B, Miguel G H, et al. Non-linear decay of building stones during freeze-thaw weathering processes[J]. Construction and Building Materials, 2013,38: 443-454.

[7] J. Ruedrich,D. Kirchner,S. Siegesmund. Physical weathering of building stones in-duced by freeze–thaw[J]. Environ Earth Sci , 2011,63:1573-1586.

[8] Takarli M, Prince W, Siddique R. Damage in granite under heating/cooling cyclesand waterfreeze-thaw condition[J].International Journal of Rock Mechanics and Mining Sciences,2008, 45(7):1164-1175.

[9] Park C, Synn, J H, Shin D S. Experiment study on the thermal characteristic of rock at low temperatures. international Journal of rock at low temeratures [J]. Int-ernational Journal of Rock Mechanics&Mining Science,2004,41 (S) :81-86.

[10] Aoki K,Hibiya K,Yoshida T.storage of refrigrrated liquefied gasses in rock caverns:characteristics of rock under very low temperatures[J].Tunnelling and UndergroundSpace Technology.1990,5(4):319-325.

[11] 陈宇龙,张科,孙欢.冻融循环作用下岩石表面裂纹扩展过程细观研究[J].土木工程学报,2019,52:1-7.

[12] 崔贺佳,夏冬,吴朝松,等.冻融循环对饱水岩石纵波波速影响的试验研究[J].金属矿山.2018,510:45-50.

[13] 田延哲,徐拴海.冻融循环条件下岩石物理力学指标相关性分析[J].矿业安全与环保.

2017,24-27.

[14] 刘华,牛富俊,徐志英,等.循环冻融条件下安山岩和花岗岩的物理力学特性试验研究[J].冰川冻土.2011,33(3):557-563.

[15] 吴刚,何国梁,张磊,等.大理岩循环冻融试验研究[J].岩石力学与工程学报.2006(S1):2930-2938.

[16] You-Liang Chen,Jing Ni, Li-Hao Jiang,etal. Experimental study on mechanical properties of granite after freeze–thaw cycling[J]. Environ Earth Sci (2014) 71:3349-3354.

[17] Yavuz H, Altindag R,Sarac S, et al.Estimating the index properties of deterioratedcarbonate rock due to freeze-thaw and thermal shock weathering[J]. International

Journal of Rock Mechanics and Ming SCIENCES &Geomechanics Abstracts.2006,43(5):767-775.

[18] Yamabe T, Neaupane K M. Determination of some thermo mechanical properties of Sirahama sandstone under subzero temperature condition[J]. International Journal of Rock Mechanics and Mining Science, 2001, 38(7): 1029-1034.

[19] Inda Y, Yokota K. Some study of low temperature rock strength [J].International J-ournal of Rock Mechanics and Ming SCIENCES &Geomechanics Abstracts.1984,21(3):145-153.

[20] 陈国庆,周玉新,魏涛,等.裂隙岩石冻融循环下裂纹扩展特征研究[J]. 金属矿山.2019:192-196.

[21] 刘希灵,刘周,李夕兵,等.劈裂荷载下的岩石声发射及微观破裂特性[J].工程科学学报.2019(11):1422-1432.

[22] 吴秋红,赵伏军,李夕兵,等.径向压缩下圆环砂岩样的力学特性研究[J].岩土力学.2018(11):3969-3975.

[23] 张慧梅,杨更社. 水分及冻融环境下岩石抗拉力学特性[J]. 湖南科技大学学报(自然科学版).2013,09:35-40.

[24] 张慧梅,夏浩峻,杨更社,等.冻融循环和围压对岩石物理力学性质影响的试验研究[J].煤炭学报,2018,43(2):441-448．

[25] 王乐华,陈招军,金晶,等.节理岩体冻融力学特性试验研究[J].水利水电技术.2016:149-153.

[26] 杨更社,奚家米,李慧军,等.三向受力条件下冻结岩石力学特性试验研究[J].岩石力学与工程学报.2010(03):459-464.

[27] 杨更社,奚家米,邵学敏,等.冻结条件下岩石强度特性的试验研究[J].西安科技大学学报.2010(03):14-18.

[28] 刘希灵,刘周,李夕兵,等.单轴压缩与劈裂荷载下灰岩声发射b值特性研究[J]．岩土力学.2019:267-274.

[29] 王林均,张搏,钱志宽,等.单轴压缩下两类脆性岩石声发射特征试验研究[J].工程地质学报,2019:699-705.

[30] 王创业,杜晓娅.基于尺寸效应的砂岩巴西劈裂声发射特征试验研究[J].矿业研究与开发.2018(06):44-48.

[31] 李果,艾婷,于斌.不同岩性巴西劈裂试验的声发射特征[J].煤炭学报.2015(4):870-881.

[32] 侯鹏,高峰,杨玉贵,等.考虑层理影响页岩巴西劈裂及声发射试验研究[J].岩土力学,2016,37(06):1603-1612.

[33] 刘波,张功,李守定,等.砂质泥岩在低温劈裂试验中的声发射研究[J].岩石力学与工程学报,2016,35(S1):2702-2709.

[34] 闵明,张强,蒋斌松,等.实时高温下北山花岗岩劈裂试验及声发射特性[J].长江科学院院报,2020,37(03):108-113.

[35] 黄炳香,程相振,陈必武,等.红砂岩单轴压缩破坏的声发射信号及时空演化特征[J].矿业研究与开发,2017,37(05):24-29.

[36] 肖福坤,刘刚,秦涛,等.拉–压–剪应力下细砂岩和粗砂岩破裂过程声发射特性研究[J].岩石力学与工程学报,2016,35(S2):3458-3472.

[37] 陈宇龙,张科,孙欢.冻融循环作用下岩石表面裂纹扩展过程细观研究[J].土木工程学报,2019,52(S1):1-7.

[38] 王江峰,王振华,臧冀川.利用RFPA~(2D)对单裂纹扩展规律的研究[J].煤炭技术,2018,37(05):26-29.

[39] 杨振琦,王述红,孟嫣然,等.基于CT扫描的花岗岩三维数值试件重构模型及应用[J].固体力学学报,2017,(06):591-600.

[40] 姜耀东,李海涛,赵毅鑫,等.加载速率对能量积聚与耗散的影响[J].中国矿业大学学报,2014,(03):369-373.

[41] 许学良.脆性岩石抗拉特性及其破裂机制的试验与细观模拟研究[D].北京科技大学,

2017.

[42] 司凯.岩石的巴西劈裂破坏及声发射特征试验研究[D].河南理工大学,2017.

学,2015,36(8):2315-2322.