基于CPTU贯入深度超前滞后效应的数值模拟研究

孔压静力触探技术(CPTU)是目前应用最广泛的原位测试技术之一。在岩土工程设计中,准确识别土层边界对确定地基土的工程性质指标如桩的持力层、地基承载力等具有重大意义。目前,岩土勘察中的土层分界是通过现场取样进行室内试验为主,静力触探等原位测试方法为辅。一些研究显示,CPTU测试数据的连续性使土层边界的确定更加精确。然而超前滞后深度的存在使基于CPTU土层分层的方法精度降低,影响了国内CPTU在这一方面的发展。采用ABAQUS软件通过给上下土层的弹性模量赋予不同的数值建立探头在层状土中的贯入模型,并且对探头贯入过程进行数值模拟。基于大量的现场试验数据提出在上软下硬和上硬下软地层条件下超前滞后深度的计算公式,为CPTU识别土层边界提供了有效的依据。

Numerical Simulation Research on the Effect of Lead and Lag ofCPTU Penetration Depth in Layered Soil

The piezocone penetration test (CPTU) is one of the most widely used in-situ test. In geotechnical engineering design, it is of great significance to accurately identify the soil boundary for determining the engineering properties of foundation soil, such as the bearing capacity of pile and foundation. At present, the boundary of soil layer in geotechnical investigation is mainly carried out by laboratory test through on-site sampling, supplemented by in-situ test methods such as static contact. Some studies have shown that the determination of soil boundary is more accurate due to the continuity of CPTU test data. However, the existence of lead and lag depth reduces the accuracy of CPTU-based soil stratification method, which affects the development of CPTU in China. ABAQUS software is used to establish the penetration model of probe in layered soil by giving different values to the elastic modulus of upper and lower soil layers, and the penetration process of probe is simulated. Based on a large number of field test data, a formula for calculating the lead and lag depth of double-layer soil under different elastic modulus is proposed, which provide support for CPTU to identify soil boundary.