系梁对桩柱式基础反射波法检测影响的计算及现场试验

根据应力波按半球面波扩展传播的特点,结合系梁(盖梁)、墩柱、桩基之间的几何尺寸关系,建立系梁(盖梁)等结构件对应力波干扰频率的计算方法并得到其分布特征。采用多通道同步采集设备结合同相轴分析方法进行桩柱式基础完整性状况跟踪测试现场试验。结果表明:桩顶自由时得到的扩径、桩底反射等信号特征可以在墩柱、系梁等施工后测试得到的信号中体现;拾振点应尽量竖向串列式排列,这种拾振方式不仅可以根据拾振点起始波峰之间的时差和拾振点间距计算结构物的应力波波速,而且不同拾振点的振动曲线能形成同相轴,便于利用同相轴分析判断桩底、盖梁(系梁)反射和其他反射体的反射。数据分析时,对异常信号应重点分析其拾取时刻,并借助测定的墩柱、系梁或盖梁的应力波波速判断其发生位置。

On the Calculation of Disturbance of a Tie Beam on a Column-pile Foundation in Tests Using Low Strain Reflected Wave Method and In-situ Verification Experiment

Assuming that a stress wave in low strain tests spreads in semi-spherical mode,a method was established to calculate the disturbance of a tie beam in response to the frequency of the stress wave.This method is related to the geometry of the tie beam,bent cap,pier,and pile. Furthermore,a test method was designed to test the integrity of piles in a column-pile system,in which multi-channel equipment was required to record the behavior of the bent cap and pile. Tests were conducted to compare the integrity of the pile during the entire column-pile system procedure.The results showed that when pile top was free,the reflection signal could be detected after tie beam and pier were constructed.Sensors should be located vertically as a linear array that will facilitate the calculation of the stress velocity and allow the recording of the behavior of the reflection from the bent cap,pile toe,etc.In regard to abnormal signals,their peak time should be analyzed to determine their location according to the stress velocity of pier,tie beam,and bent cap.It is not recommended that the abnormal signals be analyzed using only the similar or opposite-phase method as has been the previous rule in pile integrity test when pile top was free.