3D geophysical investigation methods for evaluating non-uniformity of housing site

近年来，有缺陷的房屋已经成为一个社会问题。据报道，大多数有缺陷的房屋是由地面和/或地基故障造成的。一些地基和基础的破坏是由局部不均匀地基引起的，如局部软土地基、埋置的工业垃圾和埋置的树根。然而，以往的地球物理勘探方法在很多情况下无法发现局部不均匀地基。为此，提出了一种基于波达线与振源夹角测量的局部不均匀地面位置识别方法。垂直地面运动是使用六个传感器的圆形阵列测量的。通过对数据的F-k谱分析，可以确定到达波和震源之间的角度。为了验证该方法的有效性，进行了现场调查和三维有限元分析，所提出的方法在一个住宅现场进行定位不均匀的地面位置。在该方法确定的局部不均匀地基位置进行了瑞雷波法、瑞典测深试验、动力触探试验和H/V谱分析。瑞雷波法、瑞典测深法和动力触探法在该场地的测试结果与周围的测试结果存在差异。另一方面，H/V谱的主导周期保持不变。在地下调查后，在该地点发现了大量的埋藏的烘烤泥浆。三维有限元分析，研究局部不均匀地面对波传播的影响。结果表明：（1）当传感器阵与震源之间存在局部不均匀地面时，波的到达角与震源角不同;（2）局部软地面对波传播的影响大于局部硬地面。

In recent years, defective homes have emerged as a social issue. It is reported most of the defective homes are caused by ground and/or foundation failures. Some ground and foundation failures are caused by local nonuniform ground, such as local soft ground, buried industrial junks and buried roots of a tree. However, previous geophysical investigation methods can not find out local nonuniform ground in many cases. Therefore, a method is presented for identification of local nonuniform ground position based on measurement of the angle between arrival wave and a vibration source. Vertical ground motion is measured using a circular array of six sensors. The angle between the arrival wave and the source can be determined, based on F-k spectrum analysis of the data. To examine the validity of the proposed method, field investigations and 3D FEM analysis were performed.The proposed method was performed at a housing site to locate nonuniform ground position. Rayleigh wave method, Swedish sounding test, dynamic penetration test and H/V spectrum were performed at the place where the proposed method indicated local nonuniform ground was located. The results of Rayleigh wave method, Swedish sounding test and dynamic penetration test at the place were different from those around the place. On the other hand, predominant periods of H/V spectrum remained unchanged. After the subsurface investigations, a lot of buried baked-muds were found at the place.3D FEM analysis was performed to investigate the effects of local nonuniform ground on wave propagation. It is shown that (1) the arrival wave angles differ from the source angle in case that local nonuniform ground locates between the sensor array and the source ; (2) effects of local soft ground on the wave propagation is greater than that of local hard ground.