Vol.4 No.01(2014), Article ID:13252,8 pages
DOI:10.12677/APF.2014.41001

Experimental Study and Mathematical Model on Permeability of Clayey Soil with Shear Deformation

Hongjun Lei

HydroChina Kunming Engineering Corporation, Kunming

Email: hongjunlei@126.com

Received: Jan. 13th, 2014; revised: Feb. 10th, 2014; accepted: Feb. 20th, 2014

ABSTRACT

A new seepage device was developed to measure permeability of clayey soil under different physical and mechanical status with shearing deformations. A series of seepage tests were carried out on a certain clayey soil and indicated that permeability of the soil was related with many factors, among which the shearing strain and confining pressure were the most important. Based on the testing results and mechanism analysis, a new relation model of permeability to reflect effect of physical and mechanical status was raised. The model was then fitted and checked by the testing results.

Keywords:Permeability; Shearing Deformation; Seepage; Mathematical Model

Email: hongjunlei@126.com

1. 引言

2. 试验装置和试验土料

2.1. 试验装置

2.2. 试验土料

Figure 1. Sketch map of the seepage test device

1-底座；2-量水管；3-出水管与阀门；4-X方向渗流进水管；5-Y方向渗流进水管；6-Z方向渗流进水管；7-试样；8-进水侧土工织物；9-出水侧土工织物；10-上帽；11-X方向渗流出水管；12-Y方向渗流出水管；13-Z方向渗流出水管；14-传力杆

Table 1. Physical index of the testing soil

Figure 2. Gradation curve of the testing soil

3. 典型试验结果与分析

3.1. 不同剪切应变和围压条件下的渗透性

1) 在试样承受不等向应力发生剪切应变的起始阶段，渗透系数迅速减小，随着轴向应变的增加，变化速率越来越慢，最后渗透系数基本趋于稳定。

2) 低围压下，渗透系数变化幅度较大，最大可达数十倍，而高围压下渗透系数的变化幅度相对较小，一般只有3~5倍。

3) 在低围压如100 kPa、300 kPa时，试样在轴向应变增加到某一程度时，渗透系数有反向增加趋势，但增加幅度不明显。高围压下试样的渗透系数没有反向增加现象。

4) 不同围压下的试样在产生相同的轴向应变时，围压小的试样其渗透系数较大，围压大的试样其渗透系数较小。且这种差别随围压的增加而逐步变得不明显。

3.2. 不同方向的渗透系数

Figure 3. Permeability under different axial strain

Figure 4. Permeability in different directions

4. 渗透性数学模型

4.1. 渗透系数与孔隙比的关系

4.2. 渗透系数与剪应力水平的关系

(1)

Figure 5. Permeability and void ratio in semi-log coordinate system

Figure 6. Permeability and shearing stress level in semi-log coordinate system

4.3. 土体剪切变形中渗透系数数学模型

(2)

(3)

(4)

4.4. 数学模型的空间形式

Figure 7. Dimensional curve surface of permeability

Figure 8. Calculated values and measured values of permeability

4.5. 模型拟合与验证

(5)

5. 结论

1) 基于三轴仪改进的渗透试验装置可有效用于测试试样在剪切变形过程中的渗透系数。

2) 试验结果表明，粘性土的渗透系数受诸多因素的影响，如轴向剪切应变、围压、渗透方向和渗透水压力等，其中，剪切应变和围压的影响最为显著。

3) 所提出的渗透系数数学模型一方面通过孔隙比反映土体物理状态变化对渗透性的影响，另一方面通过剪应力水平反映剪切引起的结构变化对土体渗透系数的影响。当土体仅发生等向固结时，渗透系数沿数学模型的退化形式“等向固结渗透系数线”发展，当土体发生剪切变形时，渗透系数随着“一般轨迹”运行。

4) 基于试验数据的模型拟合表明，所提出的数学模型可有效反映土体在剪切变形过程中不同物理力学状态条件下的渗透系数。

1. [1]   Chu, J. (2002) Consolidation and Permeability Properties of Singapore Marine Clay. Journal of Geotechnical and Geoenvironmental Engineering, 128, 724-732.

2. [2]   Marshall, T.J. (1958) A Relation between Permeability and Size Distribution of Pores. European Journal of Soil Science, 9, 1-8.

3. [3]   Nishida, Y., Koike, H. and Nakagawa, S. (1971) Coefficient of Permeability of Highly Plastic Clays. Proceedings of the 4th Budapest Conference on Soil Mechanics and Foundation Engineering, Budapest, 12-15 October 1971, 127- 133.

4. [4]   Garcia, I., Lovell, C.W. and Altschaeffle, A.G. (1979) Pore Distribution and Permeability of Silty Clays. Journal of the Geotechnical Engineering Division, 105, 839-856.

5. [5]   Bryant, W.R. and Richardson, M.D. (1992) Permeability and Porosity of Clayey Sediments in Seismo-Acoustics. The Journal of the Acoustical Society of America, 92, 2308-2321.

6. [6]   Chan, H.T. and Kenney, T.C. (1973) Laboratory Investigation of Permeability Ratio of New Liskeard Varved Soil. Canadian Geotechnical Journal, 10, 453-472.

7. [7]   Carpenter, G.W. and Stephenson, R.W. (1986) Permeability Testing in the Triaxial Cell. Geotechnical Testing Journal, 9, 3-9.

8. [8]   朱建华 (1989) 土坝心墙原状土的三轴渗透试验. 岩土工程学报, 4, 57-63.

9. [9]   李平, 骆亚生 (2006) 饱和土的三轴渗透试验研究. 路基工程, 6, 32-33.