山区斜坡软基路堤稳定性研究

Study on Stability of Soft Foundation Embankment in Mountain Slope

为研究山区高速公路斜坡软基路堤在填筑过程和运营期间路基易发生整体滑移工程病害的失稳机理和防治措施,达到快速有效处治路基工程病害、确保路基在建设和运营期工程安全的目的,以我国某高速公路一处典型的山区斜坡软基路堤段落的整体失稳为工程案例,进行了工程调查、地质勘察、Geo slope简化Bishop计算、FLAC3D数值模拟、现场沉降与位移实测,发现该路堤段落地基土体的抗剪强度低、稳定性差,致使坡脚处抗滑桩桩顶上部的路基填土发生了越顶变形。在准确认识失稳机理的基础上,提出了相应的工程处治技术措施。通过Geo slope软件分别对处治前、处治后的路基边坡稳定性安全系数进行了对比计算,预评了处治措施的效果。运用FLAC3D软件对处治前、处治后地基、路基的水位位移、沉降进行了模拟计算对比分析。结果表明:安全系数由处治前的0.831增长为处治后的1.452,达到规范要求;相比处治前,处治后地基、路基的水平位移和沉降均明显减小,稳定性得到了大幅度改善;数值模拟结果与现场工程实测结果基本吻合,验证了处治措施的可靠性;针对具体的斜坡软基路堤工程问题,准确认识了失稳机理,才能采用有效的处治措施。

In order to study the instability mechanism and prevention measures of subgrade engineering diseases of soft foundation embankment on expressway mountain slope which is prone to overall slip during the filling process and operation period,and to achieve the purpose of quickly and effectively treating subgrade engineering diseases and ensuring engineering safety of subgrade during construction and operation period,taking the overall instability of a typical mountain slope soft foundation embankment section of an expressway in China as an engineering case,the engineering investigation,geological investigation,Geo slope simplified Bishop calculation,FLAC3D numerical simulation,field settlement and displacement measurement are carried out.It is found that the low shear strength and poor stability of the foundation soil at the embankment section mainly led to the deformation of the subgrade fill at the top of the anti-slide pile at the slope foot.Based on the accurate understanding of the instability mechanism,the corresponding engineering treatment is proposed.Then,the safety factors of subgrade slope stability before and after treatment are compared and calculated by Geo-slope software,and the effect of treatment measures is pre-evaluated.The water level displacement and the settlement of foundation and roadbed before and after treatment are compared and analyzed by using FLAC3D software.The result shows that(1)the safety factor increased from 0.831 before treatment to 1.452 after treatment,meeting the specification requirements;(2)compared with the values before treatment,the horizontal displacement and settlement of foundation and roadbed after treatment are obviously reduced,and the stability is greatly improved;(3)the numerical simulation result is are basically consistent with the in-situ measured result,which verified the reliability of treatment measures;(3)to solve the specific engineering problems of embankment on slopes and soft foundations,effective treatment measures could be adopted only when the mechanism of instability of soft foundation embankment on slope is accurately understood.