数值模拟在高速公路软弱地基处理中的应用

Numerical Simulation of Highway Soft Foundation Treatment

尹中高速公路的地基土稳定性不能满足公路工程的要求,为了掌握该公路在施工过程中变形特征,采用有限元软件NCAP-2D对尹中高速公路施工过程进行了模拟,分析了不同桩间距、断桩两种情况下的破坏、位移特征。结果表明,旋喷桩桩顶处于塑性状态,旋喷桩桩顶侧向位移大于桩底,增加了基础的稳定性;当桩间距变化时,桩顶土和桩间土的塑形区范围、位移量呈正相关变化,桩顶附近发生塑性破坏的敏感区域;有断桩时,塑形区在断桩处分布范围明显较大,影响地基加固效果。所得结果对于此类公路的建设施工具有一定的借鉴意义。

The stability of Yinzhong highway fails to satisfy the requirements of the highway engineering. In order to know the deformation features of this highway during its construction, the FEM analysis software of NCAP-2D is used. The geotechnical material＇s nonlinear features, such as elastic-plastic relations, nonlinear joints, non-tensile characteristics, and orthotropic properties of the layered rock mass, are considered in the software. The Drucker-Prager yield criterion is applied in the numerical models, and the construction process of pile forming and soil filling are simulated with an element-free method. The basic data of displacement and stress after excavation are obtained when compared with those before excavation. Piles with different gaps and broken piles are simulated, and the plastic zone and displacement characteristics are analyzed. The results show that the top of jet grouting pile is in relatively obvious plastic state, because some loads on the soil between piles are transmitted to the piles. At the same time, the top of the piles experiences larger lateral displacement than the bottom, which could enhance the basement stability. The plastic zone and the displacement have a positive correlation when the gap between piles is changed, and the same for the soil and piles. But the area around the pile＇s top is where breakage would occur with whatever change of pile＇s gap. The plastic zone would obviously be concentrated around the broken piles, which would influence the foundation reinforcement effect. According to the field load test, after the treatment by high pressure jet grouting, the bearing capability of the foundation is, respectively, 2.08 times and 2.97 times of that of the untreated recently deposited loess and soft loess. And the actual monitoring settlement is only about 0.17 times of the calculated value. So, the treatment in this paper/s situation has a good strengthening effects. The conclusion in this paper provides some guidance for highway^s construction in the similar situations.