【作者】 于凯；

【导师】 车爱兰；

【作者基本信息】 上海交通大学 ， 岩土工程， 2012， 硕士

【摘要】 在土木工程、地震防灾等领域,地下岩土层的基本性状,尤其是横波速度构造极为重要,其在工程场地和结构的地震响应分析、建(构)筑物的设计与安全运行等方面都是不可或缺的基础资料。地脉动勘探由于不需要人工震源,而作为信号的地脉动则是由交通振动等人类活动和风暴、海浪等自然现象引起的环境噪音,被认为是一种简便、快速、低成本、对环境无特殊要求,同时又对环境不产生影响的勘探手段。由于长周期脉动信号十分微弱,其幅度一般只有几微米,因此要求探测仪器必须频带宽、灵敏度高、噪声低才能采集到高保真的有效波形。对于勘探深度数十米以下的大深度勘探,地脉动的信号主要来源于海洋的浪潮和风暴等自然现象,作为岛国的日本以及中国的沿海地区,信号强,比较容易观测,然而从沿海向中国大陆内部,远离海洋,地质和环境等条件变化大,是否能有效地观测到这些地区的长周期脉动信号还需研究,另外,地脉动信号的特性,包括信号强弱和频谱特性等方面的研究也亟待明确。在详细阐述地脉动观测、长周期地脉动观测和地脉动台阵观测的研究现状及存在的问题的基础上,从地脉动观测原理出发,以沿海至远离海岸线的内陆地区为研究区域,并在沿海和中间过渡区域设置对比点,通过定期长时间连续地脉动长周期观测及大量单点地脉动观测,开展中国广域内陆地区脉动信号的观测和研究,讨论了长周期地脉动观测测点布置、设备及参数选取、数据的质量保证措施、长周期地脉动特征及其在场地卓越特征评价中的应用等,探查从沿海到内陆地区地脉动的空间变化规律,尤其是长周期脉动特征的变化规律,评价地脉动的频谱稳定性,详细了解了沉积层厚度、横向变化,并对沿海地区及内陆地区的地脉动探测的适用性进行比较。在长周期地脉动观测在地震防灾中的应用方面,首先以上海市内东西向地脉动观测数据为基础,采用单点谱比法对上海市东西向覆盖土层分布进行反演,并与以往的大深度地下调查资料进行对比,对长周期地脉动观测在地下调查中的适用性进行了评价。在把握了我国广域地区长周期地脉动特征的基础上,针对沿海城市上海市实施了地脉动台阵观测,详细讨论了地脉动台阵观测方法、分析方法,研究了利用地脉动台阵观测方法推测地下剪切波速度构造的适用性。更多还原

【Abstract】 Shear wave velocity (Vs) of soil is one of the key parameters used in seismic engineering and geotechnical engineering; which is an important parameter in evaluation of dynamic properties of a site. It is well known that the micro tremor observation is one of the most convenient methods to investigate the dynamic characteristics of the surface ground for no need of man-made explosion source which caused by human activities such as traffic vibrations and environmental noise from storm and ocean waves. The micro tremor is a kind of geophysics prospecting and drilling information, which is of abundant intention such as the information of soil site and engineering geological condition and so on.As the long period microtremor signal is very faint, which range can reach only a few microns, it is needed a widely frequency band, high sensitive and low noise detector to obtain the collect high fidelity effective wave data. Since the major source of the microtremor signal to reach exploration depth up to tens of meters is the ocean wave, storm and such natural phenomena, For the, it is easy to obtain strong signal in Japan and the coastal area in China. However, it is needed to discuss whether an effective long period microtremor signal can be obtained in mainland which far away from the ocean in Chinese, where the geological and environmental condition changes a great deal. Also, the research about microtreomor signal’s properties including the strongest and the weakest signals and the spectrum feature needs to be discussed urgently.Based on the detailed describe of the present status and the problems on the microtremor survey, long period microtremor survey and microtremor array survey, using microtremor observation principle and choosing the area from coastal region to the part far away from coastline with several comparison points setting on the coastal region and the intermediate area, a series of regular long-term continuous long period microtremor survey and a great number of single points microtremor survey are conducted. Chinese inland area’s microtremor signal are observed and studied. The measurement method of long period microtremor survey, equipment and parameter selection, data quality guarantee measures and long period microtremor properties and its application in the site predominant characteristic evaluation are discussed. The variation of characteristics of microtremor from coast to inland areas is clarified, especially the variation of the long period microtremor. The spectrum stability of the microtremor is evaluated. Detailed information about thickness of sediment layers and the lateral variation are revealed, with the comparison to the microtremor survey’s applicability in the coastal area and inland areas.In the aspect of the long period microtremor survey’s application in earthquake and disaster prevention, there are many works have been done. First, based on the east-west microtremor survey data in Shanghai, single point spectrum analogy method is used for the east-west cover soil distribution inversion in Shanghai. It is compared to previous large scale underground survey data, and the underground survey application of the long period microtremor survey is valued. Then, understanding the long period microtremor feature in Chinese wan area, we carry out array microtremor survey in allusion to the coastal city Shanghai. In addition to this, array microtremor survey method and its analytical method is detailed discussed, also the applicability that using the array microtremor survey method to calculate underground shear wave velocity distribution.更多还原