| For a long time,the comprehensive protection of subgrade slope has been a common problem in highway construction.In the process of construction and development of railway,highway,reservoir area and other venues engineering,a lot of subgrade slope protection technology issues are involved,and the major difficulty is for largescale consequent rock slope.At present,the range of limit angle for skew slope has not been perfect;as the main reinforcement measure for treatment of bedding slope,anchor cable,frame beam and anti-slide pile have been widely used in various fields,but there is a lack of systematic study on the coordination effect between the three.Therefore,in this paper,take typical sections of Chongqing Fuling-Fengdu-Shizhu expressway construction project as an example.Based on the limit equilibrium theory,limit angle of sloping along the bedding slip for skew slope is analyzed and verificated;and the treatment of anchor-frame-pile combined anti slide system for K27 slope is analyzed and evaluated systematically.The main research contents and innovative achievements are as follows:(1)Based on analyzing the stability impact of angle between skew slope level and slope line,limit value of sloping along the bedding slip for skew slope is 30 degrees.Through the three dimensional numerical simulation,it is concluded that when the angle is 10 degrees,horizontal displacement and safety factor appear obvious inflection points,and impact of the angle for slope is at the largest;when the angle is more than 30 degrees,influence of bedding for slope stability is less to not consider.That means:limit angle of sloping along the bedding slip for skew slope is 30 degrees.(2)In view of the large bedding high rock bedding slope,combined with the "edge excavation and timbering",based on the typical sliding-tensile fracturing,the paper puts forward multi level sliding-tensile fracturing mode.The multi level sliding-tensile fracturing mode is more appropriate to describe the deformation of large bedding slope.(3)The mathematical mechanics model of bedding rock slope is established.Based on the model,the finite element numerical model of anchor-frame-pile combined anti slide system for K27 slope is constructed in three conditions.So,the anchor-frame-pile combined anti slide system is proposed,and the coordination effect law of the system is analyzed:in this system,internal force of anchor cable,frame beam and anti-slide pile can coordinate with each other to ultimately show a more efficient ability to resist sliding force of slope.That is to say,for sliding force,the shared value of anchor cable is greater,the shared value of sliding pile is smaller;on the contrary,the shared value of anchor cable is smaller,the shared value of sliding pile is coordinated greater.Through mutual coordination,a more efficient resistance characteristic for slope sliding is achieved in the.whole system.(4)Based on the analysis of landslide formation mechanism,it is concluded that due to the weak structure of the sandstone and mudstone,the K27 slope is prone to slip under the condition of rainfall.According to the analysis of stereographic projection for fracture surface and slope,the slope aspect(328 degrees)and the rock tendency(323 degrees)intersect in small angle,which belongs to bedding slope.At this time,the slope stability is controlled by the rock strata,and the potential failure mode is plane sliding along the dip angle of rock stratum.So the stability of the slope is poor.By calculation,the safety factor of the slope under natural condition is 1.07,and the safety factor of the slope under the rainstorm condition is 0.94,which belongs to the unstable slope,and needs to carry on the anti-slide treatment.(5)Combined the investigation on the K27 largescale rock consequent cutting slope and the landslide formation mechanism,a single method has been unable to fully meet the governance requirements.Finally,the anchor-frame-pile combined anti-slide system is established for K27 slope.By calculating of SRM(a 3D numerical simulation method),the safety coefficient of K27 slope under natural condition reaches 1.74 with the action of the system,which belongs to the stable slope.(6)Considering the effect of sinusoidal vehicle on slope crest,coordination mechanism of anchor-pile support system for the bedding slope is established.Rebuilding road of K27 slope brings another problem in design of anti-sliding.By simulating the action of sinusoidal vehicle on slope crest,it is concluded after analyzing the free vibration and time history:under dynamic loading on slope crest,the shared value of anchor cable and frame beam can coordinate with each other;response sensitivity of anchor cable and frame beam for dynamic load is inconsistent,which is mainly concerns with the size and position of the load;concept of reasonable coordination interval for anchor-pile support system under dynamic load is put forward and the evaluation effect for slope stability is effective,which proves it is a new index to evaluate and a new method to control the slope under dynamic load.(7)Based on numerical simulation,with the action of the anchor-frame-pile combined anti-slide system,the safety coefficient of K27 slope under the condition of heavy rain reaches 1.49,which means the governance effect is good to meet the specification requirements.(8)Based on the monitoring data calculation,force of anchor cable in the direction of sliding is 115.92kN/m,and force of anti-slide pile in the direction of sliding is 225.64kN/m.This shows that decline force is shared by anchor cable and anti-slide pile,33.94%of which is shared by anchor-frame system and the remaining 66.06%is shared by anti-slide pile.All values are in the range of design,which means the slope is safety and the governance effect is good.(9)Based on orthogonal experimental design,optimization design and variance sensitivity analysis is done for K27 slope.Conclusions are as follows:in the anti-sliding ability,anti-slide pile is larger than anchor-frame system;anchorage length and anchor root number plays a major role against slip;anti-sliding capacity of vertical beam is greater than the cross beam;section dimensions and length of anti-slide pile plays a major role against slip.On this basis,the final optimization scheme not only saves resource but also increases the safety factor of the slope.The safety factor of slope treaded as the optimization scheme is 1.56,which meets the requirement of the specification. |
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