不同含水率下红黏土软化模型及强度试验研究

doi:10.11872/j.issn.1005-2518.2020.03.130

摘要/Abstract

摘要：

为研究重塑红黏土的软化特性和抗剪强度与含水率之间的关系，以山西长治地区重塑红黏土为试验材料，进行了不同含水率下的三轴不固结不排水试验。试验结果表明：山西长治地区重塑红黏土在含水率和围压较小的情况下易发生宏观剪切破坏，其应力—应变曲线出现了明显软化现象，采用改进的应力—应变软化模型能够较好地模拟试验曲线的变化趋势；山西长治地区重塑红黏土中矿物质伊/蒙间层含量较高，土体内部存在较大孔隙，随着含水率和围压的增加，试样由宏观剪切破坏变为塑性破坏，当含水率为15%~24%时，其不排水抗剪强度与含水率之间呈线性关系。该项研究成果为认识特殊红黏土的破坏机理及软化现象提供了参考，同时也为进一步建立特殊红黏土数学模型提供了理论基础。

关键词: 含水率, 红黏土, 变形特征, 应变软化模型, 抗剪强度

Abstract:

In engineering geology，red clay especially refers to the high plastic clay，which color is brownish-red or brown-yellow and so on，formed by lateralization of exposed rocks of the carbonate system.The red clay sample in this study was taken from 20 m underground in Changzhi area of Shanxi Province，China，which is a special red clay with high pores，high shrinkage and strong hydrophilic properties.The basic physical parameters of red clay were first measured according to the standard for geotechnical test methods（GB/T50123-1999），besides，the mineral composition of the red clay was appraised by X diffraction analysis.The results show that the content of the I/S layer in the red clay is high.In order to study the softening characteristics of the remodeling of red clay and the relationship between shear strength and moisture content，undrained triaxial tests was carried out using the TSZ-2 automatic strain control three-axis instrument.A total of 24 cylindrical specimens were produced during the experiment，each cylindrical sample size is 39.1 mm×80 mm.Because the moisture content of the original soil is about 17.0% to 23.7%，so the moisture content of remodel red clay is 15%，18%，21%，24% respectively.And confining pressures of 100 kPa，200 kPa and 300 kPa were applied respectively at each moisture content.The relationship between moisture content, principal stress difference，cohesion and internal friction angle was obtained from the experiment.When the moisture content changes, the remold red clay of Changzhi area of Shanxi Province have different failure forms.It would have macroscopic shear failure under low moisture content and confining pressure，meanwhile，the stress-strain curve has obviously softening phenomenon, and the modified stress-strain softening model can be better to simulate the test curve.Due to the high mineral content of I/S layer of the remolded red clay in Changzhi area，Shanxi Province，China，so the red clay has a large pore inside，with the increase of moisture content and confining pressure，the specimen from macro-shear damage to plastic damage，besides，when the moisture content is 15% to 24%，there is a linear relationship between the non-draining anti-shear strength and moisture content of this kind of red clay.The research results in this paper can provide reference for the related foundation treatment in the special red clay area of Changzhi，Shanxi Province，China，and also provide a theoretical basis for the further mathematical model of special red clay.

Key words: water content, red clay, deformation characteristics, strain softening model, shear strength

中图分类号:

TU411.7

李怀鑫, 林斌, 陈士威, 王鹏. 不同含水率下红黏土软化模型及强度试验研究[J]. 黄金科学技术, 2020, 28(3): 442-449.

Huaixin LI, Bin LIN, Shiwei CHEN, Peng WANG. Study on the Softening Model and Strength of Red Clay at Different Water Content[J]. Gold Science and Technology, 2020, 28(3): 442-449.

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参数名称	取值	参数名称	取值
干密度/（g·cm^-3）	2.08	比重Gs	2.74
液限/%	39.37	重度/（kN·m^-3)	20.98
塑限/%	20.34	孔隙比e/%	31.78

土样	矿物成分相对含量/%					混层比/%
土样	I/S	K	I	C	S	I/S	C/S
红黏土	79	5	16	-	-	20	-

围压/kPa	拟合系数		相关系数/%
围压/kPa	k₁/（×10^-3）	k₂/（×10^-3MPa）	相关系数/%
100	-0.0519	1.2983	0.9678
200	-0.0611	1.5376	0.9593
300	-0.0719	1.8039	0.9637

含水率/%	围压σ₃/kPa	E_p/kPa	E_max	（σ₁-σ₃）_t	ε_t	（σ₁-σ₃）_p	ε_p	α_EP	b₁	b₂	b₃	b₄	b₅
15	100	61.67	339.70	399.9	13.75	539.6	8.75	5.51	2.8911	-0.2432	0.0716	3.1776	1.6901
	200	40.37	229.91	-	-	625.7	15.50	5.69	3.7145	-0.1735	-0.0025	-	-
	300	43.16	232.51	-	-	733.8	17.00	5.35	2.8074	-0.2422	0.0642	-	-
18	100	30.56	107.73	-	-	359.1	11.75	3.53	1.7701	-0.2483	-0.0421	-	-
	200	30.96	153.47	-	-	464.5	15.00	4.96	3.0566	-0.1914	-0.0113	-	-
	300	50.68	221.93	-	-	532.2	10.50	4.38	2.7939	-0.1797	-0.0530	-	-
21	100	15.90	46.33	-	-	159.0	10.00	2.91	1.3262	-0.2723	-0.0900	-	-
	200	12.96	90.11	-	-	184.8	14.25	6.95	4.3715	-0.1892	0.0491	-	-
	300	18.20	110.47	-	-	213.8	11.75	6.07	3.6334	-0.2038	0.0431	-	-
24	100	6.98	22.60	-	-	87.3	12.50	3.24	1.6133	-0.2502	-0.0704	-	-
	200	8.64	29.73	-	-	108.0	12.50	3.44	1.6684	-0.2567	-0.0416	-	-
	300	10.26	30.00	-	-	120.6	11.75	2.92	1.2321	-0.2890	-0.0699	-	-

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