Study On Calculation Method For Beam Spacing Of Anchor Frameworks In Soil Slope Engineering

Anchor frameworks is a commonly used slope reinforcement structure in engineering practice,but the design theory of beam spacing is not perfect.In view of the anchor frameworks structure of similar soil slope,considering the shallow surface stability and the overall stability control requirements of the slope,the calculation methods of the spacing between the horizontal beams and the longitudinal beams are established respectively by using the plastic limit analysis method,and the numerical simulation method is adopted to analyze and verify the results.The main results are as follows:(1)Rainfall is an important inducement for the instability of the shallow surface of the slope.Under rainfall infiltration,the shallow surface soil of the slope gradually changes from unsaturated state to saturated state.The decrease of shear strength of the soil results in the sliding instability of the slope.The sliding mode of the soil between beams can be taken as the parallel slope-curve failure mode.(2)Based on the upper bound method of limit analysis,the rotating failure mechanism and multi-block failure mechanism for stability analysis of shallow surface,as well as the rotating failure mechanism for overall slope stability analysis of anchored slope,are established,and the expressions for calculating the spacing between horizontal beams and longitudinal beams are derived.(3)The influence of design safety factor,soil strength parameters,slope gradient and infiltration softening depth on the spacing of beams is discussed.With the increase of soil strength parameters,the spacing between beams increases nonlinearly;with the increase of design safety factor,slope gradient and infiltration softening depth,the spacing between beams decreases gradually.(4)The influence of the setting position of anchor bolt(cable),including the initial position of anchorage and the spacing of multi-row anchors,the inclination angle of anchor,the internal friction angle and cohesion of soil,the safety factor of slope stability design and the geometrical shape of slope on the spacing of longitudinal beams is analyzed.With the increase of anchorage angle,the spacing between longitudinal beams decreases,and the reasonable anchorage angle is in the range of 5-20 degrees;with the increase of anchorage spacing along slope direction,the spacing between longitudinal beams increases;with the increase of uphill angle and downhill angle,the spacing between longitudinal beams decreases,and the spacing between longitudinal beams is more sensitive to the change of downhill angle;with the increase of soil strength parameters,the spacing between longitudinal beams increases nonlinearly.(5)Using FLAC3 D numerical simulation method,the influence characteristics of the spacing between horizontal beams and longitudinal beams on the stability of anchored slope are analyzed.The calculation results of stability coefficient and potential slip surface are basically consistent with the theoretical analysis results.The example analysis shows that the maximum error of slope stability coefficient obtained by the two methods is 8.27%.The research results of reasonable beam spacing calculation method for anchor frameworks structure in this paper can provide guidance and reference for anchor frameworks design in practical engineering,and have important theoretical significance and application value.