Joint bearing mechanism of structure and foundation for gravity anchor block of suspension bridge

Based on the gravity anchor block engineering in Xuanwei Bank of Puxuan Highway, three kinds of computing schemes such as no backfilling & no pretension, no backfilling & pretension and backfilling & pretension were designed, and the mechanical mechanisms and fail modes of gravity anchor block and foundation were analyzed on basis of numerical test.Bearing mechanism presents that when the loads are less than 8 times of design load, plastic deformationcan't occur, the working situation is elastic, the maximum of deformation locates on the interface of structure and foundation, the friction effect is dominant, the tensile stress zone under foundation is controllable, and the anti-slipping and anti-overturning stability of anchor block is stable or controllable.When the loads are larger than 12 times of design load, the plastic zone expands step by step, and until to 20 times of design load, the plastic zone is cut-through.The plastic strain under the structure and the structure deformation of anchor block aspect are observable.The rock mass clamped by structure is broken.The clamping effect is dominant.The tensile stress zone under foundation is uncontrollable.The anti-slipping and anti-overturning stability of anchor block is unstable or uncontrollable.The prestress of anchor block acts only before the compatible deformation of structure and foundation, and the action fades away after the compatible deformation.Backfilling can greatly improves foundation's stress state and structure's torsional deflection, anti-slipping and anti-overturning stability, so the enhancement effect can be considered within the scope of allowable deformation.The joint deformation and bearing mechanisms of gravity anchor block and foundation are comprehensively performed by friction effect, clamping effect and backfilling effect.Monitoring result denotes that the interface safety of anchor block and foundation can be controlled by monitoring the tensile and compressive stress of base bottom, and the monitoring data are less than 3 MPa that is allowable bearing capacity of foundation.The anti-slipping stability of the structure is monitored by using the deflection and the deeply horizontal displacement of foundation, and the practical monitoring values are less than 1 mm.The anti-overturning stability of structure is monitored by using the uneven sedimentation of structure corners, and the inclined value is less than 0.006.The inner maximum monitored temperature of mass concrete is less than 60℃, the temperature difference of input and output water is less than 15 ℃, the temperature difference of anchor block's inner and surface is less than 20℃, and the post-peak cooling rate is less than 3 ℃·d^-1.The changing amplitudes of stresses of anchor cables are less than 5% of design stress.