單樁受地震動與斷層錯動引致地盤變位作用下反應之擬靜力分析模式

Abstract

樁基礎深埋於土層中常會受到地盤變位作用而造成損壞。地盤變位可能由地震或斷層錯動等因素所造成，然而，目前針對樁基礎受地震作用下之反應，大多關注上部結構慣性力作用之影響，而地盤變位對基礎之影響常被忽視，且在基礎受斷層作用下之反應亦較少以地盤變位的角度來探討。本研究主要分為兩個部分：第一部分探討樁基礎受地震作用下之反應，並針對其所引致之地盤位移剖面，發展出一擬靜力分析模式，以地盤位移側推分析之方式來預估基礎之受震反應；第二部分探討樁基礎受斷層作用下之反應，歸納出反應機制，並以此為基礎，發展一擬靜力分析模式來推估基礎受斷層作用下之反應。 在地震動引致地盤變位方面，本研究以傅有為（2021）之動態模型為基礎，透過數值分析軟體SAP2000進行基礎受震動態分析，並進一步發展擬靜力側推分析模式，探討基礎受地震動所引致之地盤位移剖面作用下反應，針對不同土壤條件及輸入運動，歸納出一組能有效預估基礎動態反應之特徵位移剖面。研究結果顯示：透過地盤最大位移剖面進行側推分析能掌握基礎受震下之樁身位移反應包絡線，且地表最大位移及加速度位移剖面能大致掌握基礎受震下之樁身內力反應包絡線。 為了探討基礎受斷層作用下之反應，本研究透過三維有限元素分析，針對斷層種類、錯動量及基礎與斷層錯動間之相對距離進行參數分析，並依基礎與土壤間相互作用關係，歸納出其反應機制。正斷層依照基礎與上盤土壤是否接觸，共區分為兩種機制，逆斷層則根據其引致之應變集中區及斷層破裂帶作用於基礎位置，區分為五種機制。 基於上述分析結果，本研究進一步以溫克基礎為架構，發展分析基礎受斷層所引致之地盤位移剖面作用下反應之擬靜力模式，並以三維有限元素分析結果進行驗證。依照各機制之作用原則，分別以不同側推分析方式進行擬靜力分析，此分析模式能大致上掌握基礎受斷層作用下之反應。

Pile is a deep foundation and is often damaged by ground displacement. Ground displacement may be caused by factors such as earthquake excitation and fault dislocation. However, if there is a superstructure, the response of the pile is mainly contributed by the inertial force under an earthquake, while the influence of ground displacement is often neglected. Moreover, the response of the pile under the fault dislocation is less discussed. This study has two parts. (1) Discusses the response of the pile under the earthquake. This study uses SAP2000 to conduct the dynamic analysis and develops the pseudostatic analysis model to decide the characteristic ground displacement. The results show that the maximum ground displacement profile can predict the response envelope of the pile displacement under the earthquake, and the ground displacement profiles of the time that the displacement and acceleration occur at the ground surface can predict the response envelope of the pile internal force under the earthquake. (2) Discusses the response of the pile under the fault dislocation. This study uses 3D-ABAQUS to conduct a series of parameter analyses carried out on the types of faults, fault offset, and the distance between the foundation and the fault dislocation. The mechanism of the pile response was summarized according to the interaction between the foundation and the soil. Normal faults can be divided into two mechanisms according to whether the foundation and the hanging wall are in contact, and reverse faults can be divided into five mechanisms according to the pile position of the strain concentration zone and fault rupture zone caused by the fault. Next, based on the results, develop a pseudostatic analysis model by SAP2000 to predict the response of the pile under the fault.