旋喷静压复合桩芯桩-水泥土界面强度特性试验研究

Study on the strength characteristics of core pile⁃cemented soil interface of jet grouting jacked composite piles

旋喷静压复合桩具有单桩承载力高、受力合理,可在既有建筑加固与改造工程的低净空条件下施工等优势;旋喷静压复合桩具有双层荷载传递模式,芯桩-水泥土界面和水泥土-桩周土界面是控制旋喷静压复合桩承载特性和破坏模式的关键因素;针对此特性,对旋喷静压复合桩的芯桩-水泥土界面进行研究,通过水泥土试块强度试验,验证了水泥掺量、水灰比和龄期对水泥土无侧限抗压强度的影响,并通过界面强度特性试验,证明了芯桩-水泥土界面侧阻力与水泥土无侧限抗压强度有关,得出了钢管-水泥土界面和混凝土-水泥土界面的粘结系数。试验表明:水泥土的无侧限抗压强度受水泥掺入量和含水量的双重控制,随水灰比的增加而减小,对于不同水灰比的水泥土,存在最优水泥掺量;芯桩-水泥土界面的极限侧阻力与水泥土强度存在近似线性关系,钢管-水泥土界面的粘结系数平均值为6.66%;芯桩-水泥土界面在受荷过程中经历了弹性阶段、脆性破坏阶段和剪切滑移阶段。

Jet grouting jacked composite pile has a high bearing capacity of a single pile,reasonable force⁃bearing,can be in the existing building reinforcement and renovation project of the low clearance conditions of construction advantages.The rotary static pressure composite pile has double layer load transfer mode,core pile⁃cemented soil interface and cemented soil⁃pile surrounding soil interface are the key factors to control the bearing characteristics and destruction mode of jet grouting jacked composite pile.For this feature,study on the core pile⁃cemented soil interface of jet grouting jacked composite pile.Through the strength test of the cemented soil test block,the influence of cement content,cement ratio and age on unrestricted compressive strength is verified,Through the interface strength characteristic test,it is proved that the lateral resistance of core pile⁃soil interface is related to the unlimited compressive strength of cemented soil,and the bonding coefficient of steel pipe⁃cemented soil interface and concrete⁃cemented soil interface is obtained.The test shows that the compressive strength of cemented soil is controlled by the amount of cement and water content,and decreases with the increasing water ash ratio.For cemented soil with different water⁃cement ratios,there is an optimal cement mix.There is an approximate linear relationship between the ultimate side resistance of the core pile⁃cemented soil interface and the cemented soil strength,and the average bond coefficient of the steel pipe⁃cemented soil interface is 6.66%.The core pile⁃cemented soil interface goes through the elastic stage,brittle failure stage and shear slip stage in the loading process.