高应力状态下钙质砂的一维压缩特性及试验影响因素分析
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摘要
中高应力状态下钙质砂的一维压缩试验可以得到试样的轴向屈服应力、压缩指数等特性,但试样的侧向力很难准确测得。为了研究钙质砂的一维压缩特性,开展17组高应力状态下钙质砂与石英砂的一维压缩对比试验和17组ABAQUS三维有限元数值模拟,得到一维压缩试验中应变片位置、套筒粗糙度、壁厚和长度对试验结果的影响。结果表明,相同相对密实度下石英砂的压缩模量是钙质砂3～4倍,压缩模量随相对密实度的增大而增大。钙质砂和石英砂的屈服应力分别约为2和10 MPa,此后颗粒开始大量破碎,压缩指数分别约为0.90和0.65。通过数值计算与试验结果对比发现,若试验中通过测量套筒外壁环向力反算试样径向力,测试点布置于试样中部时误差最小。试验时套筒内壁应尽量光滑,在满足变形要求的前提下,套筒壁厚越薄反算结果越接近真实值。
The yield stress and compressive index of calcareous sand under high stress conditions can be investigated by one-dimensional compression tests,but the lateral stress is difficult to be measured. This paper conducted 17 1 D compression tests and 17 three-dimensional finite element numerical simulations on calcareous and silica sands. The effects of the tube roughness,thickness and lengths were analyzed. It is found that the compressive modulus of silica sand is approximately 3–4 times that of calcareous sand with an almost identical relative density. The compressive modulus increases with increasing relative density. The yield stresses of calcareous and silica sands are approximately 2 MPa and 10 MPa,respectively,beyond which amount of particles begin crush. The compression index of calcareous and silica sand is approximately 0.90 and 0.65,respectively. By comparing the computed and measured results,it is found that if the lateral stress is back-calculated by the outer tangential stress in tests,the stress state at the center of the samples is reasonable. Fulfilling the requirement in deformation,a smooth inner surface and a thin wall of the tube can efficiently decrease the monitoring error.
The yield stress and compressive index of calcareous sand under high stress conditions can be investigated by one-dimensional compression tests,but the lateral stress is difficult to be measured. This paper conducted 17 1 D compression tests and 17 three-dimensional finite element numerical simulations on calcareous and silica sands. The effects of the tube roughness,thickness and lengths were analyzed. It is found that the compressive modulus of silica sand is approximately 3–4 times that of calcareous sand with an almost identical relative density. The compressive modulus increases with increasing relative density. The yield stresses of calcareous and silica sands are approximately 2 MPa and 10 MPa,respectively,beyond which amount of particles begin crush. The compression index of calcareous and silica sand is approximately 0.90 and 0.65,respectively. By comparing the computed and measured results,it is found that if the lateral stress is back-calculated by the outer tangential stress in tests,the stress state at the center of the samples is reasonable. Fulfilling the requirement in deformation,a smooth inner surface and a thin wall of the tube can efficiently decrease the monitoring error.
引文
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[14]王者超,李术才.高应力下颗粒材料一维力学特性研究(I):压缩性质[J].岩土力学,2010,31(10):3 051-3 057.(WANG Zhechao,LI Shucai.One-dimensional mechanical behavior of granular material under high stresses(Part I):compression behavior[J].Rock and Soil Mechanics,2010,31(10):3 051-3 057.(in Chinese))
[2]TERZAGHI K,PECK R B.Soil mechanics in engineering practice[M].New York:John Wiley and Sons,Inc.,1948:242-251.
[3]HAGERTY M M,HITE D R,ULLRICH C R,et al.One-dimensional high pressure compression of granular media[J].Journal of Geotechnical Engineering,1993,119(1):1-18.
[4]YAMAMURO J A,BOPP P A,LADE P V.One-dimensional compression of sands at high pressures[J].Journal of Geotechnical Engineering,122(2):147-154.
[5]NAKATA Y,KATO Y,HYODO M,et al.One-dimensional compression behavior of uniformly graded sand related to single particle crushing strength[J].Soils and Foundations,2001,41(2):39-51.
[6]KAMER S L,CHESTER F M,KRONENBERG A K et al.Subcritical compaction and yielding of granular quartz sand[J].Tectonophysics,2003,377:357-381.
[7]WANG X Z,JIAO Y Y,WANG R.Engineering characteristics of the calcareous sand in Nansha Islands,South China Sea[J]Engineering Geology,2011,120(1/4):40-47.
[8]WANG X Z,WANG R,JIN Z C,et al.Investigation of engineering characteristics of calcareous soils from fringing reef[J].Ocean Engineering,2017,134:77-86.
[9]LV Y R,LI F,LIU Y W,et al.Comparative study of coral sand and silica sand in creep under general stress states[J].Canadian Geotechnical Journal,2017,54(11):1 601-1 611.
[10]吴京平,褚瑶,楼志刚.颗粒破碎对钙质砂变形及强度特性的影响[J].岩土工程学报,1997,19(5):49-55.(WU Jingping,CHU Yao,LOU Zhigang.Influence of particle breakage on deformation and strength properties of calcareous sands[J].Chinese Journal of Geotechnical Engineering,1997,19(5):49-55.(in Chinese))
[11]张家铭,汪稔,石祥锋,等.侧限条件下钙质砂压缩和破碎特性试验研究[J].岩石力学与工程学报,2005,24(18):3 327-3 331.(ZHANG Jiaming,WANG Ren,SHI Xiangfeng,et al.Compression and crushing behavior of calcareous sand under confined compression[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(18):3 327-3 331.(in Chinese))
[12]张季如,祝杰,黄文竞.侧限压缩下石英砂砾的颗粒破碎特性及其分形描述[J].岩土工程学报,2008,30(6):783-789.(ZHANGJiru,ZHU Jie,HUANG Wenjing.Crushing and fractal behaviors of quartz sand-gravel particles under confined compression[J].Chinese Journal of Geotechnical Engineering,2008,30(6):783-789.(in Chinese))
[13]史旦达,周健,贾敏才,等.考虑颗粒破碎的砂土高应力一维压缩特性颗粒流模拟[J].岩土工程学报,2007,29(5):736-742.(SHIDanda,ZHOU Jian,JIA Mincai,et al.Numerical simulations of particle breakage property of sand under high pressure 1Dcompression condition by use of particle flow code[J].Chinese Journal of Geotechnical Engineering,2007,29(5):736-742.(in Chinese))
[14]王者超,李术才.高应力下颗粒材料一维力学特性研究(I):压缩性质[J].岩土力学,2010,31(10):3 051-3 057.(WANG Zhechao,LI Shucai.One-dimensional mechanical behavior of granular material under high stresses(Part I):compression behavior[J].Rock and Soil Mechanics,2010,31(10):3 051-3 057.(in Chinese))