【摘要】 针对富水软弱地层综合管廊中SMW工法桩(型钢水泥搅拌桩)力学特性与优化设计问题,利用有限元软件MIDAS-GTS NX建立SMW工法桩力学模型,分析不同支护桩桩径、不同型钢布置形式、不同型钢尺寸、不同支撑轴力下SMW工法桩水平位移等力学特性的变化规律,确定SMW工法桩最优设计。在综合管廊K0+080-K0+275标段对型钢水泥土搅拌桩不同的施工工艺参数进行试桩试验,确定SMW工法桩施工工艺参数。结果表明:当SMW工法桩桩径由0.55 m增加至0.85 m时,桩身水平位移降低幅度为28.9%,通过增加桩直径可以有效控制桩体水平位移;型钢的翼缘与腹板尺寸增加对基坑变形影响较小,由于翼缘处于受力侧则对于支护结构的变形更加敏感;型钢不同布置形式对基坑变形影响较大,型钢密插型布置桩身最大水平位移比插一跳一型布置减小18.4%;增加钢支撑预加轴力可有效减小围护结构变形,按照设计轴力的50%～80%取值较为合理。结合对现场施工便利性和施工效率的影响,最终确定某地下综合管廊K0+080-K0+275标段支护方式为采用?650@450水泥土五轴搅拌桩内插HM500×300×11×18型钢,型钢布置形式采用插一跳一型。在富水软弱地层使用SMW工法桩施工参数水灰比为1.3,水泥掺量为20%最为合理,优选施工方案现场监测数据与数值模拟变化规律较为契合,并在地下综合管廊工程中成功运用,取得理想效果。更多还原

【Abstract】 Aiming at the mechanical characteristics and optimal design of SMW construction method piles(section steel cement mixing piles) for comprehensive pipe gallery in water-rich weak stratum, the mechanical model of SMW construction method piles is established by using FE software MIDAS-GTS NX, the variation rules of mechanical characteristics such as the horizontal displacements of SMW construction method piles with different supporting pile diameters, different section steel layouts and sizes, different supporting axial forces and so on are analyzed, and the optimal design of SMW construction method piles is determined. In the K0+080-K0+275 section of the comprehensive pipe gallery, different construction process parameters of the section steel cement-soil mixing piles are tested and the SMW construction method pile construction process parameters are determined. The result shows that(1) when the diameter of SMW construction method pile increases from 0.55 m to 0.8 5 m, the horizontal displacement of the pile body decreases by 28.9%, and the horizontal displacement of the pile body can be effectively controlled by increasing the pile diameter;(2) the increase of sizes of the flange and web of the section steel has little influence on the foundation pit deformation, and the flange is more sensitive to the deformation of supporting structure because it is on the stressed side;(3) different layout forms of the section steel have a greater influence on the foundation pit deformation, the maximum horizontal displacement of the pile body in the layout of section steel close insertion is 18.4% less than that in the layout of one empty and one insertion;(4) the increase of supporting pre-adding axial force can effectively reduce the deformation of the envelope structure, and it is more reasonable to take the value of 50%-80% of the designed axial force. Considering the influence on the site construction convenience and efficiency, it is determined that the K0+080-k0+275 bid section of an underground comprehensive pipe gallery to be finally supported by ?650@450 cement soil 5-axle mixing pile with inserted HM500×300×11×18 section steel, and the layout of section steel adopts the layout of one empty and one insertion. It is most reasonable to use SMW construction method piles in water-rich weak stratum with water-cement ratio of 1.3 and cement content of 20%. The field monitoring data of the optimized construction scheme is in good agreement with the variation rule of numerical simulation, and has been successfully applied in the underground comprehensive pipe gallery project and achieved ideal result.更多还原