考虑基础刚度影响的风机梁板式桩筏基础模型试验研究

梁板式桩筏基础作为新型风机基础,前景广阔,适当优化结构,可节约成本。采用大型室内模型试验,研究了梁板式桩筏基础在不同筏板刚度情况下的受力变形特性,同时讨论了桩土荷载分担比的关系。研究表明,在工作荷载范围内,适当增大筏板刚度,桩平均轴力增加,外圈桩承担的荷载增大,内圈桩的轴力减小,环梁及肋梁弯矩减小,但继续增加刚度,对桩身轴力、环梁弯矩、肋梁弯矩的影响并不大;随着荷载的增大,土体承担的荷载比逐步增大,趋于稳值。随着梁板式基础刚度增加,基础内外差异沉降减少,但是达到一定刚度后再增加刚度对变形影响较小。梁板式基础刚度的变化会影响基底反力分布的均匀性,且存在一个最优刚度,使基础底部反力分布最为均匀,本次试验中12梁的梁板式基础基底反力比6梁和实体基础更均匀。桩基的分布和梁的分布存在相互影响,改变梁的分布会影响桩顶力,而桩基在梁底下又会使梁的应力产生重新分布。研究成果可为设计桩筏基础提供参考依据。

Model test on piled beam-slab raft foundation for wind turbines considering raft rigidity

As a new foundation for wind turbine on land, piled beam-slab foundation has a broad prospect .The optimized structures properly can reduce costs. To investigate the bearing and deformation characteristics of piled beam-slab foundation under vertical loads under different raft rigidities, a large-scale model test is carried out, which also research the ratio of the force carried by pile and that carried by soil. The research shows that within the range of work load, average pile axial force increases with the increase of the raft rigidity; the axial force of the outer-ring-piles increases while the axial force of inner-ring-piles reduces. The moment of the ring beam and the ribbed beam decrease when the rigidity continues to increase after a certain value, there is little effect on axial force, moment of the ring beam and ribbed beam. With the increase of the stiffness of the beam-slab foundation, the differential settlement of the foundation decreases. However, this trend will become insignificant as the stiffness increases to a certain value. The variety of rigidity of the piled beam-slab foundation could make a difference on the uniformity of subgrade reaction. Besides, there is an optimal stiffness that can make the foundation reaction distribution most uniform. In the experiment, the subgrade reaction distribution of the piled-beam-slab foundation with 12 beams is more uniform comparing to the foundation with 6 piles and block foundation. And there is an optimal rigidity for piled beam-slab foundation, which makes the soil beneath the foundation beared more loads while piles do less. The distribution of piles and beams produces mutual effects on each other. When the distribution of beams changes, the forces of the pile top will be affected. And piles under the beams will also result in beam stress redistribution. In actual project, the rigidity of caps should be optimized and the research results can provide reference for the design of piled beam-slab foundation.