侧向受荷桩周土体内部位移场的模型试验研究

Model tests on displacement field of internal soil induced by laterally loading pile

针对常规室内模型试验仅限于土体表面位移量测的缺点,利用玻璃砂、正十二烷和白矿油混合液合成人工透明土,设计侧向受荷桩周土体位移测量试验系统,研究桩周土内部的体移变化规律.该系统主要包括激光器、数码相机、水平加载装置、应变采集装置和计算机等.激光穿过透明土,形成目标观测切面,数码相机捕捉激光和颗粒相互作用产生的散斑图像并存储与计算机中.在试验过程中,土体位移图片通过PIVview2C软件进行分析,可以获得土体内部的位移场.从不同深度来测量土体内部变形,可以更直观地观测到侧向受荷桩周土体的位移发展变化规律.试验结果表明,侧向受荷桩土体内部位移主要集中在桩前接近土表面的浅层土体,桩前土内部体在水平面内呈纺锤体状,土体深度从2.4 D(D为桩直径)增加为3.8 D时,桩前土体影响范围从7.5 D减小为6 D,土体最大位移减小了约25%.

The internal soil deformation induced by a laterally loaded pile was analyzed using the transparent soil.The transparent soil was made of baked quartz and a pore fluid with a matching refractive index.An optical set-up consisted of two lasers,two digital cameras,a lateral load system,a model pile,a strain gauge testing instruments and a computer.A distinctive speckle pattern was generated by the interaction of the laser in transparent soil.Camera 1 was above the model box with its optical axis perpendicular to the ground surface set and Camera 2was set in front of the model box with its optical axis perpendicular to the vertical profile.Two cameras were used to continuously capture a series of pictures of the transparent soil model induced by a laterally loaded pile.A set of laser speckle images obtained before and after the tests were used to calculate the relative displacement field.Two laser devices were used to illuminate different targeted sections close to the pile.Results illustrated that the soil displacementsoccurred near the ground surface in front of the pile.The influence zone in front of the pile decreased from7.5times pile diameter(D)to 6D and the maximum displacement decreased about 25% when the soil depth increased from 2.4D to 3.8D.