基于透明土的成层土中CPT贯入试验研究

卢谅; 何兵; 肖亮; 王宗建; 马书文; 林浩鑫

doi:10.11779/CJGE202212008

基于透明土的成层土中CPT贯入试验研究 English Version

卢谅^{1, 2,},
何兵^{1, 2},
肖亮^{1, 2},
王宗建³,
马书文^{1, 2},
林浩鑫^{1, 2}

1.
重庆大学土木工程学院, 重庆 400045
2.
重庆大学山地城镇建设与新技术教育部重点实验室, 重庆 400045
3.
重庆交通大学河海学院, 重庆 400074

基金项目:

国家自然科学基金面上项目 52178314

详细信息

作者简介:
卢谅(1981—)，女，博士，副教授，博士生导师，主要从事岩土工程等方面的研究工作。E-mail：luliangsky@163.com

中图分类号: TU43
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出版历程
- 收稿日期: 2021-09-21
- 网络出版日期: 2022-12-13
- 刊出日期: 2022-11-30

Experimental study on CPT penetration in layered soil based on transparent soil

LU Liang^{1, 2,},
HE Bing^{1, 2},
XIAO Liang^{1, 2},
WANG Zong-jian³,
MA Shu-wen^{1, 2},
LIN Hao-xin^{1, 2}

1.
School of Civil Engineering, Chongqing University, Chongqing 400045, China
2.
Key Laboratory of New Technology for Construction of Cities in Mountain Area, Ministry of Education, Chongqing University, Chongqing 400045, China
3.
College of River & Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074, China

摘要

摘要: 静力触探(CPT)在成层土中的贯入阻力受土层界面影响显著，但目前对探头穿越土层界面时出现的“超前、滞后”现象仍缺乏系统的解释，利用贯入阻力划分土层仍依靠工程经验。采用透明土模型试验模拟探头在成层土中的贯入过程，通过观测探头阻力变化曲线和探头附近土体的变形情况，研究CPT在成层土中的贯入机理。结合扩孔理论和Mohr-Coulomb准则，提出锥尖阻力影响深度的计算方法，结合试验数据和理论计算，得到上层砂土下层黏土的塑性区影响范围与贯入阻力曲线的“超前”深度一致。并利用PFC分析成层土中，CPT贯入阻力反映的层间界面效应的影响因素。结果表明，CPT贯入过程中土体变形与土体自身强度、初始地应力和土层界面位置有关；相邻两层土体的强度差异对“超前、滞后”深度有显著影响。利用本文结论根据土体的塑性区影响范围与土体的超前深度一致对土层进行划分，对比目前的土层划分的复杂性，可直接依据该方法对土层直接划分，提高了土层划分的效率和准确性。
- 透明土 /
- 静力触探 /
- 扩孔理论 /
- 离散元模拟
Abstract: The penetration resistance of cone penetration test (CPT) in layered soil is significantly affected by the soil interface, but there is still a lack of systematic explanation for the phenomenon of "leading and lagging" when the probe crosses the soil interface. The division of soil layers through the penetration resistance still depends on engineering experience. A series of transparent soil model tests are carried out to simulate the penetration process of the probe in layered soil. The penetration mechanism of CPT in the layered soil is studied by observing the resistance curve of the probe and the deformation of soil near the probe. Combining with the cavity expansion theory and the Mohr Coulomb criterion, the method for calculating the influence depth of the cone resistance is proposed. Based on the test data and theoretical calculation, it is found that the influence range of the plastic zone in the two-layered soil with the upper sand and the lower clay is consistent with the "leading" depth of the penetration resistance curve. PFC is used to analyze the influence factors of the interface effct reflected by the CPT penetration resistance in layered soil. The results show that the soil deformation during CPT penetration is related to the soil strength, the initial in-situ stress and the position of soil interface. The strength difference between two adjacent layers of soil has a significant influence on the "leading and lagging" depth. Based on the research results, the soil layer is divided according to the plastic zone of soil and the leading depth of soil. Compared with the current complex methods of soil layer division, the proposed method can improve the efficiency and accuracy of soil layer division.
- transparent soil /
- CPT /
- cavity expansion theory /
- discrete element modeling

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图 1 CPT贯入透明土模型装置

Figure 1. Model device of CPT penetrating transparent soil

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图 2 贯入阻力随深度变化曲线

Figure 2. Curves of penetration resistance versus depth

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图 3 单层土体位移矢量图

Figure 3. Displacement vector diagram of single-layer soil

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图 4 贯入单层黏土不同深度时位移矢量图

Figure 4. Diagram of displacement vector when penetrating into a single layer of clay at different depths

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图 5 成层土位移矢量图(上层黏土下层砂土)

Figure 5. Diagram of displacement vector of layered soil (upper clay and lower sand)

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图 6 成层土位移矢量图(上层砂土下层黏土)

Figure 6. Diagram of displacement vector of layered soil (upper sand and lower clay)

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图 7 柱状孔扩张问题的计算模型

Figure 7. Model for cylindrical cavity expansion problem

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图 8 简化模型

Figure 8. Simplified model

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图 9 理论预测和试验数据

Figure 9. Theoretical prediction and experimental data

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图 10 数值模拟土体位移矢量图

Figure 10. Diagram of simulated soil displacement vector

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图 11 贯入阻力模拟结果

Figure 11. Simulated results of penetration resistance

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图 12 贯入速度的影响

Figure 12. Influences of penetration speed

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图 13 探头半径的影响

Figure 13. Influences of probe radius

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图 14 土体参数的影响

Figure 14. Influences of soil parameters

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表 1 透明土试样的基本物理力学指标

Table 1 Basic physical and mechanical indexes of transparent soil

试样	ρ(干)/(g·cm^-3)	ρ(油)/(g·cm^-3)	E/MPa	ν	φ₀/(°)	c/kPa	e
熔融石英砂	1.464	1.532	40	0.32	34	0	0.663
无定形硅粉	0.056~0.230	1.100	1.5	0.55	14~18	11	1.224

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表 2 贯入模型试验工况

Table 2 Test conditions of penetration model

工况	土层类型
工况1	单层砂土
工况2	单层黏土
工况3	上层黏土下层砂土
工况4	上层砂土下层黏土

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表 3 土体参数变化工况图

Table 3 Working conditions of soil parameters

工况	${E}_{砂土}$ /(N·m^-1)	${E}_{黏土}$ /(N·m^-1)	黏结强度/N	f_砂	f_黏
1	1×8	5×10⁵	400	0.35	0.12
2	1×8	1×10⁷	600	0.35	0.20
3	1×8	5×10⁶	500	0.35	0.17
4	5×7	5×10⁶	500	0.30	0.17
5	5×8	5×10⁶	500	0.40	0.17

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表 4 数值模拟参数设置

Table 4 Setting of numerical parameters

工况	土层类型	法向刚度kn/(N·m^-1)	切向刚ks /(N·m^-1)	f	黏结强度/N
1	土层1	1×10⁸	1×10⁸	0.35	—
2	土层2	5×10⁶	5×10⁶	0.20	500
3	土层1	1×10⁸	1×10⁸	0.35	—
3	土层2	5×10⁶	5×10⁶	0.20	500
4	土层2	5×10⁶	5×10⁶	0.20	500
4	土层1	1×10⁸	1×10⁸	0.35	—

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