基于低围压土体的三轴试验数据拟合及其软件实现
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摘要
岩土三轴试验的重要目的,是通过岩土破坏时的轴压和围压绘制摩尔应力圆,根据摩尔圆包络线的斜率和截距来确定岩土的抗剪强度参数(黏聚力c和内摩擦角φ)。前人研究表明,在低围压情况下(σ3<10 MPa),岩土破坏符合摩尔-库伦准则,此时,岩土的轴向破坏应力与围压呈线性关系。实际工程中的河口、海洋软土通常均符合该特征关系,因而对低围压土体的三轴试验数据处理具有广泛的现实意义。本文根据摩尔-库伦理论,运用最小二乘原理对低围压土体三轴数据进行线性拟合。通过编制C++程序,采用牛顿迭代法求解抗剪强度参数,进一步,通过MFC类库搭建用户界面,将以上计算方法实现软件化。在此基础上,对不同河域、海域软土试验数据进行软件拟合,以对比验证软件的准确度和精确性。本文所用计算方法精度高,迭代时间短,收敛速度快,相应软件界面清晰,操作简单,使用方便,可广泛适用于各低围压软土土体。
One of the important purposes of the triaxial test of rock and soil is to draw the Mohr stress circle through the axial pressure and confining pressure, and to determine the shear strength parameters(cohesion and internal friction angle) according to the slope and intercept of the envelope of the Mohr circles. Previous studies have shown that, under low confining pressure, the strength parameters of the rock and soil determined by Mohr Coulomb strength theory can meet engineering requirements. At this time, the axial stress varies with confining pressure linearly. In practical engineering, the marine soft soil usually conforms to the characteristic,thus, it is of great practical significance to the data fitting of the triaxial test of the soil under low confining pressure. In this paper, the linear fitting was conducted with the use of the least square method according to the theory. The cohesive force and interior friction angle was obtained with C++ program and the Newton iter-ative method. Furthermore, the user interface was built with MFC to make the algorithm software realization.Based on the above, the experimental data of soft soil in different river and ocean areas were compared with our software to verify the accuracy of the software. The algorithm in this paper has a high accuracy, a short iteration time and a fast convergence rate, the software has a clear interface and is simple and convenient to the user, which can be widely used in the soft soil under low confining pressure.
One of the important purposes of the triaxial test of rock and soil is to draw the Mohr stress circle through the axial pressure and confining pressure, and to determine the shear strength parameters(cohesion and internal friction angle) according to the slope and intercept of the envelope of the Mohr circles. Previous studies have shown that, under low confining pressure, the strength parameters of the rock and soil determined by Mohr Coulomb strength theory can meet engineering requirements. At this time, the axial stress varies with confining pressure linearly. In practical engineering, the marine soft soil usually conforms to the characteristic,thus, it is of great practical significance to the data fitting of the triaxial test of the soil under low confining pressure. In this paper, the linear fitting was conducted with the use of the least square method according to the theory. The cohesive force and interior friction angle was obtained with C++ program and the Newton iter-ative method. Furthermore, the user interface was built with MFC to make the algorithm software realization.Based on the above, the experimental data of soft soil in different river and ocean areas were compared with our software to verify the accuracy of the software. The algorithm in this paper has a high accuracy, a short iteration time and a fast convergence rate, the software has a clear interface and is simple and convenient to the user, which can be widely used in the soft soil under low confining pressure.
引文
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[11]田兆阳,李平,郑志华,等.软土动力特性动三轴试验研究[J].地震工程学报, 2017, 39(1):95-99.
[12]孙红,袁聚云,赵锡宏.软土的真三轴试验研究[J].水利学报, 2002(12):74-78.
[13]陈超斌,武朝军,叶冠林,等.小应变三轴试验方法及其在上海软土的初步应用[J].岩土工程学报, 2015, 37(增刊2):37-40.
[14]徐瑞民.二元非线性方程组求根的牛顿迭代法[J].山东轻工业学院学报, 2009, 23(4):89-91.
[15]姜爽.淮河入江水道崇湾段特殊软土的物理力学性状试验研究[D].南京:东南大学, 2015.
[2]李小磊,吴云刚.求解c、Φ值的软件开发及试验验证[J].安全环境工程, 2010, 17(1):103-106.
[3]邹宗兴,唐辉明,徐伟,等.三轴试验摩尔包络线模型拟合[J].地质科技情报, 2011, 30(3):118-122.
[4]长江水利委员会长江科学院. SL 264-2001水利水电岩石试验规程[S].北京:中国水利水电出版社, 2001.
[5]王星辉.三轴剪切总应力强度指标的回归求值[J].地球科学与环境学报, 2004, 26(1):52-54.
[6]杨同,徐川,王宝学,等.岩土体三轴试验中的粘聚力与内摩擦角[J].中国矿业, 2007, 16(12):104-107.
[7]王艳芳,范明桥,周密.基于遗传算法的莫尔-库伦强度直线模拟[J].人民长江, 2007, 38(11):57-59.
[8]吴力平,张建标,李刚.砂土抗剪强度数值模拟的关键技术研究[J].浙江海洋学院学报:自然科学版, 2010, 29(6):575-578.
[9]李驰,王建华,刘振纹.软土地基单桶基础循环承载力研究[J].岩土工程学报, 2005, 27(9):1 040-1 044.
[10]马惠彪,孙钰杰,高远,等.沿海滩涂区宕土-排水板作用地基的固结研究[J].浙江海洋学院学报:自然科学版, 2015, 34(4):403-406.
[11]田兆阳,李平,郑志华,等.软土动力特性动三轴试验研究[J].地震工程学报, 2017, 39(1):95-99.
[12]孙红,袁聚云,赵锡宏.软土的真三轴试验研究[J].水利学报, 2002(12):74-78.
[13]陈超斌,武朝军,叶冠林,等.小应变三轴试验方法及其在上海软土的初步应用[J].岩土工程学报, 2015, 37(增刊2):37-40.
[14]徐瑞民.二元非线性方程组求根的牛顿迭代法[J].山东轻工业学院学报, 2009, 23(4):89-91.
[15]姜爽.淮河入江水道崇湾段特殊软土的物理力学性状试验研究[D].南京:东南大学, 2015.