Research purposes:The research on protection measures of subgrade isolation is weakly while the new or extension structures closed to existing ballastless track on high-speed railway subgrade.In particular,there is not special disposal measures and design methodologies for the introduction of existing ballastless track upon high-speed railway subgrade.To study the key solutions of the above mentioned issues,combined with the construction of Qufu-Linyi high speed railway,analysis of critical distance,subgrade fillers,foundation treatment and construction safety for the introduction of existing ballastless track on soil subgrade of Beijing-Shanghai high-speed railway is conducted.Research conclusions:(1) The isolation measures between new railway subgrade and existing ballastless track on high -speed railway subgrade can be neglected when critical distance is more than 50 m.(2) 0.6 m thickness gravel plus 0.6 m thick high strength reinforced lightweight concrete plus general lightweight concrete can be suggested as subgrade structure for the instruction of ballastless track.(3) The control effects of additional settlement for existing ballastless track on high-speed railway subgrade through micro steel tube pile was basically identical with cement fly-ash gravel pile,high-pressure rotary jet grouting pile and replacement of lightweight concrete.(4) The additional settlement of existing ballastless track on high-speed railway subgrade can be controlled effectively by using isolated piles,meanwhile,the control effects of additional settlement increased with the length of isolated piles,but small influence of spacing method.(5) The disturb of existing ballastless track on high-speed railway subgrade increased with the number of isolated piles excavated at the same time,therefore,the number of isolated piles excavated at the same time should be controlled reasonably.(6) The research results can be used as a reference method to introduce ballastless track upon high-speed railway subgrade.%研究目的:邻近既有高铁无砟轨道路基新建或扩建建(构)筑物,路基隔离防护措施研究相对薄弱,尤其是引入既有无砟高铁并轨段路基的处置措施及设计方法近乎空白.为研究引入既有无砟高铁接轨段路基工程设计关键技术,本文结合鲁南高速铁路的建设,开展鲁南高铁引入京沪高铁曲阜东站接轨段路基的临界距离、路基填料、地基处理及施工安全等分析.研究结论:(1)路基紧邻距离大于50 m时,新建铁路路基与既有无砟路基间可不采取隔离处置措施;(2)建议采用0.6m厚级配碎石+0.6 m厚高强加筋轻质混凝土+一般轻质混凝土作为引入无砟轨道接轨段路基结构形式;(3)微型钢管桩、CFG桩、高压旋喷桩、换填轻质混凝土在控制既有无砟高铁路基附加沉降的效果上表现基本一致;(4)隔离桩可有效抑制既有无砟高铁路基面的附加沉降,隔离桩桩长越长,附加沉降控制效果越好,隔离桩间隔方式对附加沉降影响较小;(5)隔离桩同时开挖的桩数越多,既有无砟高铁路基受扰动程度明显增大,隔离桩同时开挖的桩数应控制在合理范围内;(6)该研究成果可为引入无砟高铁接轨段路基工程建设提供参考.
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