三轴试样绝对体积测量方法研究

蔡阳; 李林; 路毅

doi:10.11779/CJGE202112017

三轴试样绝对体积测量方法研究 English Version

南京林业大学土木工程学院,江苏　南京　210037

详细信息

作者简介:
蔡阳(1996— ),男,硕士研究生,主要从事土工测试技术研究。E-mail：caiyang2019@njfu.edu.cn

中图分类号: TU411
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出版历程
- 收稿日期: 2021-03-01
- 网络出版日期: 2022-11-30
- 刊出日期: 2021-11-30

Measuring absolute volume of triaxial soil specimens

College of Civil Engineering, Nanjing Forestry University, Nanjing 210037, China

摘要

摘要: 三轴试验过程中的土样体积是用于分析土体应力应变特性所需的一个基本参数。近年来,基于图像分析的方法越来越广泛地应用于土样在三轴试验过程中的体积测量。然而,基于图像分析方法测量所得结果仅仅是试样的相对体积变化,并非试样绝对体积。为了测量三轴试验过程中试样的绝对体积,综合运用摄影测量原理、光线追踪、和最小二乘优化技术,测定了覆盖试样表面点云的三维位置；通过对点云进行三角网格划分、端部截断、插值、并扣除橡皮膜体积计算得到土样在三轴试验过程中的绝对体积；同时,还针对性地开发出了用于实现上述分析步骤以及相关测量结果后处理的配套软件,GeoTri3D。为验证该绝对体积测量方法的可行性,开展了一个标准钢柱试验、一个饱和砂土和三个非饱和粉土试样的三轴试验。钢柱与饱和砂土的三轴试验结果表明该方法能够成功实现三轴试样在试验过程中任意时刻的绝对体积测量；此外,通过对粉土试样表面三维点云的进一步分析所得的土样应变云图能够真实再现三轴试验过程中的土样全局变形过程。
- GeoTri3D /
- 摄影测量 /
- 绝对体积 /
- 三轴试样 /
- 全局变形
Abstract: The soil volume in triaxial tests is an essential parameter to characterize stress and strain behaviors of soils. In recent years, more and more image-based methods have been developed for the triaxial tests on deformation measurement of soils. However, the measured results are only the relative volume change of specimens, not their absolute volume. In order to measure the absolute soil volume in triaxial tests, the photogrammetry principle, optical ray tracing and the least square optimization are used to measure the three-dimensional position of point clouds on the soil surface. The absolute volume of the soil specimens during triaxial tests is then obtained through triangulation, end cut and interpolation based on the obtained point clouds. Meantime, a software package, GeoTri3D, is developed to implement the above-mentioned steps and post processing of the measured results. In order to validate the proposed method, triaxial tests are conducted on a standard steel cylinder, a saturated sand specimen, and three soil specimens. The results obtained from the validation tests indicate that the proposed method can successfully and accurately capture the absolute volume of the soil specimens during triaxial tests at different time of interests. In addition, based on the analysis on the triangular meshes, the strain contour plots can be generated, which facilitates the visualization of the deforming process of soils during triaxial tests.
- GeoTri3D /
- photogrammetry /
- absolute volume /
- triaxial specimen /
- full-field deformation

HTML全文

图 1 坐标系的建立以及系统设置

Figure 1. Setup of coordinate system and measurement system

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图 2 钢柱试验

Figure 2. Tests on a steel cylinder

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图 3 光线追踪过程

Figure 3. Tracing process of optical ray

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图 4 三角网格和插值

Figure 4. Generation of triangular mesh and interpolation

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图 5 饱和砂土样的三轴剪切试验结果

Figure 5. Triaxial test results on saturated sand

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图 6 土样在不同时刻的三角网格

Figure 6. Evolution of triangular mesh

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图 7 不同围压下的土样试验结果 (5, 20, 60 kPa)

Figure 7. Results of specimens tested under different confining pressures (5, 20, 60 kPa)

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图 8 轴向应变

Figure 8. Axial strain

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图 9 试样剪切带与轴向应变图

Figure 9. Failure plane and axial strain

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表 1 试样参数

Table 1 Information of specimens

试样	围压/ kPa	含水率/%	直径/mm	高度/mm
钢柱	0		61.77	124.99
饱和砂	50		71.18	118.43
粉土A	5	9.46	61.82	124.95
粉土B	20	9.58	61.82	125.05
粉土C	60	9.72	61.79	124.98

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表 2 相机校核结果

Table 2 Calibrated results of camera

参数	理想化前	理想化后
f/mm	55.7901	55.7901
M/(pixel)	5568	5568
N/(pixel)	3712	3712
F_x /mm	23.9809	24.5611
F_y /mm	16.0000	16.3726
P_x /mm	11.8583	12.2806
P_y /mm	7.9973	8.1863
K₁/(10^-5)	6.410	0
K₂/(10^-8)	0	0
P₁/(10^-6)	2.167	0
P₂/(10^-6)	-2.283	0

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表 3 钢柱体积

Table 3 Volumes of steel cylinder

插值倍数	空气中体积/ cm³	压力室内体积/ cm³
0	368.793	368.753
2	376.372	376.331
4	376.983	376.941
6	377.151	377.110
8	377.220	377.179
16	377.297	377.255

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表 4 饱和砂土的顶面方程参数

Table 4 Information of top end plane of saturated sand specimens

位移/mm	a	b	c
0	-0.010	-0.010	138.43
2	-0.006	-0.016	136.63
4	-0.002	-0.018	134.66
6	0.002	-0.021	132.64
8	0.006	-0.023	130.65
10	0.012	-0.025	128.62
13	0.019	-0.029	125.62
16	0.022	-0.032	122.59
20	0.028	-0.031	118.61

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施引文献(5)

期刊类型引用(2)

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