采空区公路下伏废弃立井混凝土球面盖帽力学性能研究

Study on Mechanical Properties of Concrete Spherical Cap for Abandoned Shaft Under Goaf Highway

为了研究公路下伏废弃立井混凝土球面盖帽及其平面盖板力学性能,采用ANSYS建立其有限元模型,研究不同厚度盖板、不同矢跨比盖帽以及不同填土厚度下的盖板和盖帽的力学性能,研究结果表明:①混凝土平面盖板,随着盖板厚度的增大,第一主应力极值随之减小,盖板底部中心始终会存在拉应力;②混凝土球面盖帽,当矢跨比为2∶16、3∶16、4∶16、6∶16时,混凝土球面盖帽局部存在拉应力,当矢跨比为5∶16、7∶16、8∶16时,混凝土球面盖帽整体受压,均不存在拉应力;③随着土体厚度的增大,混凝土平面盖板的拉应力随之增大,混凝土球面盖帽最大主应力绝对值随着土体厚度的增大而增大;④厚度相同时,平面盖板第一主应力极值为拉应力,且大于球面盖帽。可见:由于盖板力学特征,其底部存在拉应力,从长期考虑,会产生微裂缝,进一步导致钢筋锈蚀,危害行车安全,球面盖帽合理调整矢跨比,整体受压,耐久性能好。

In order to study the mechanical properties of concrete spherical cap and plane cap of abandoned shaft under highway,the finite element model is established by ANSYS.The mechanical properties of cap and cap with different thickness,rise span ratio and fill thickness are studied.The results show that:①with the increase of cover thickness,The extreme value of the first principal stress decreases,and there will always be tensile stress in the center of the bottom of the cover plate.②For the concrete spherical cap,when the rise span ratio is 2∶16,3∶16,4∶16 and 6∶16,the concrete spherical cap has local tensile stress;when the rise span ratio is 5∶16,7∶16 and 8∶16,the concrete spherical cap is compressed as a whole and there is no tensile stress.③With the increase of soil thickness,the tensile stress of concrete plane cover plate increases;the absolute value of maximum principal stress of concrete spherical cap increases with the increase of soil thickness.④When the thickness is the same,the extreme value of the first principal stress of the plane cover plate is tensile stress,which is greater than that of the spherical cover cap.It can be seen that due to the mechanical characteristics of the cover plate,there is tensile stress at the bottom.In the long term,micro cracks will be generated,which will further lead to reinforcement corrosion and endanger driving safety.The spherical cover cap can reasonably adjust the rise span ratio,which is under overall pressure and has good durability.