Mechanical Performance Test of Pile-Slab Subgrade Structure in Strongly Developed Karst Area
In the design and construction of high speed rail ballastless tracks in strongly developed karst areas,the stability of karst strata and the control of subgrade settlement are key to ensuring the safety of train operation.The low pile plate subgrade structure with embedded rock at the bottom of the pile not only solves the problem of additional load on the karst roof,but also basically eliminates the compression settlement of the covering soil layer.It is a relatively stable subgrade design scheme in areas with strong karst development.In order to study the mechanical properties of ballastless track pile plate structure subgrade in strongly developed karst areas,field tests were conducted based on some high Railway.The distribution pattern of train loads in the basic body of the high speed railway and the mechanical characteristics of the pile plate structure were analyzed.The results show that under the operating conditions of trains with speeds of 300～350 km/h,the train load on the subgrade top was down transmitted almost along the 45° direction,the vertical transmission of train dynamic loads mainly affects the range of 5.0 m below the roadbed surface,and the effect of action is significant within a range of 2.7 m of the roadbed.The calculation adopts standardized methods of TB 10001-2016 Code of Design of Railway Subgrade,the measured values are smaller than the calculated values,which is biased towards safety.The stress on the three layers of steel bars inside the bearing plate is relatively uniform and small due to the reaction force of the bottom soil of the plate on the bearing plate.For sections with lower risk of karst collapse,the calculation of the pile plate structure can appropriately consider the reaction of the soil between the piles,thereby reducing engineering investment.
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