Study On Settlement Of High Fill Foundation Under Continuing Heavy Rainfall In Mountain Area

With the rapid development of western economy, the construction of mountainousairport in the west leads to rapid development of high fill foundation. High fillfoundations in mountainous airport have the characteristics of large body mass，largeheight，undulating bedrock and not flat terrain. The study area not only has the abovecharacteristics but also is located in rainy area, with high fill foundation filled withrelatively large pore. So the rainwater are more likely to get into high fill foundationcausing additional settlement in it. How to accurately calculate the settlement anddiscrepancy settlement in natural condition and caused by rainwater infiltration isneeded to solve. Presented in this thesis are water injection test, pit excavation in thespot,3D numerical model that were made for the purpose of systematically and deeplyinvestigating the settlement and discrepancy settlement laws. Rainfall infiltration depthlaw and settlement rules in high fill foundation under continuing heavy rain are deeplystudied, and the effect of dynamic compaction with different compaction levels in highfill foundation are evaluated. The main research contents and results in this thesis are asfollows.①Permeability coefficient of high fill foundation are obtained through in-sitewater injection test. Its value is5.891×10-4cm/s. And the rules that initial infiltrationrate decreases with water content increasing in high fill foundation are revealed.According to the filtration depth obtained by pit excavation in the spot, the laws offiltration are revealed.②Settlement and discrepancy settlement laws. in the valley site, slope site, thecenter of valley site and high fill site are analyzed base on3D numerical model builtaccording to the contour map of the project with suffer and ANSYS. And relationshipbetween rainwater infiltration depth and settlements is revealed. Filtration depth arefound under different continuing heavy rain duration, and Settlement and discrepancysettlement laws in different sites shown above are analyzed. The results reveals that innatural condition there is a linear relationship between the settlement and the height ofhigh fill foundation: y=0.0344x-0.377, R2=0.992.As the height of high fill foundationincreases, the ratio of settlement of high fill foundation to the height of fill foundationincreases. At the bottom of the slope the ratio is2.96%, and1.13%at the top of the highfill foundation. At the cheuch it shows that large settlement is in the middle,1.354m,and in the side of the cheuch, discrepancy settlement is1.185m. At the thickness of the fill foundation it shows that the settlement is almost thesame,1.865m, and discrepancy settlement is0.180m.At the longitudinal direction of thecheuch, the settlement is small for the3D-restraint of the cheuch,1.350m, and2.012min the flat place, discrepancy settlement is0.666m.At the slope the largest settlement isat the bottom1.752m, and discrepancy settlement is1.150m. The simulation result indifferent rainfall conditions reveals that as the depth of infiltration increases thesettlement increases. And the relationship between them is: y=0.0154x+1.9824andR2=0.9524.In condition3(depth of infiltration is21m), the largest settlement is2.383m,18.1%larger than in natural condition. The influence of filtration on discrepancysettlement is restricted by the height of high fill foundation. At the cheuch in condition3discrepancy settlement increases0.167m,14.1%bigger than in condition1.③According to dynamic compaction test result in study area, the settlement anddiscrepancy settlement laws in high fill foundation handled with different compactionlevels in different sites shown above are analyzed based on3D numerical model builtThe simulation results reveals that in natural condition the settlement in compactionlevel3000kN.m is obviously small than that in compaction level2000kN.m. At thecheuch the settlement decreases by0.471m,34.8%; at the thickness of the fillfoundation, by0.631,33.8%, at the longitudinal direction of the cheuch, decreases by0.662m,32.9%; at the slope decreases by0.567m,32.4%. The settlement in compactionlevel4000kN.m is obviously small than that in compaction level3000kN.m, thesettlement decreases by decreases by0.230m,22.9%at the cheuch; decreases by0.252m,20.4%at the thickness of high fill foundation; decreases by0.276m,20.4%atthe longitudinal direction of the cheuch; decreases by0.242m,20.4%at the slope. Thediscrepancy settlement in compaction40000kN.m is0.593m,20.4%less than that incompaction2000kN.m at the cheuch; and0.719m,47.6%at the slope. Because thediscrepancy settlement in the thickness of high fill foundation and at longitudinaldirection is small, the effectiveness is small by enhancing the compaction level.Through the above, conclusions can be got: the settlement and discrepancy settlementdecreases as the compaction level increases. In the filtration of rainfall condition, therules are similar as in the natural condition. A dynamic compaction method that canmeet the requirements on settlement and discrepancy settlement both in constructionperiod and post-construction period has been given out by comparing differentcompaction levels. In the worst condition the settlement is0.119and discrepancysettlement0.081m, so the compaction level4000kN.m can meet the requirement of the projection.④By orthogonal test design, sensitivity analysis of physical parameters of highfill foundation on settlements are made, and the rules are revealed by range analysis onnumerical modeling results. On the basis of BP neutral net, anti-analysis is madethrough the settlement of high fill foundation, and results of anti-analysis indicates thatanti-analysis to high fill foundation settlement can meet the construction requirement ondeformation. The study reveals that the anti-analysis of settlement of high fillfoundation is accurate. The biggest error is in ES,6.7%.The settlement based onnumerical model has less error,5.02%.