自然與人工邊坡和建物之地震行為研究

Seismic Behaviors of Natural and Man-made Slopes with Buildings

張貴榮(Guei-Rung Jang)

指導教授 ： 張德文

淡江大學/工學院/土木工程學系碩士班/碩士(2012年)

https://doi.org/10.6846/TKU.2012.00900

摘要

坡地建物耐震設計對於位處地震頻繁的我國而言，相當重要，但有關的文獻資料卻付之闕如，故本研究針對此一課題進行探討。
本研究使用PLAXIS有限元素軟體，並參考台北地層鑽探資料，建置邊坡模型，輸入921地震歷時，並以建築耐震設計規範所訂的30年、475年、2500年再現週期所對應的最大地表加速度0.12g、0.29g、0.51g進行邊坡受震行為分析。其模擬分為三部分：(1)自然邊坡受震行為模擬 (2)建物與邊坡互制關係 (3)人工擋土邊坡受震行為觀察。望藉由模擬，了解邊坡受震所產生的反應及趨勢，進而提供邊坡設計之參考使用。
研究結果顯示：(1)邊坡受震而尚達破壞前，最大位移發生在坡面，坡頂次之。邊坡破壞後，坡趾位移量最大。(2)邊坡受震時，若坡高不變，改變坡角，將直接影響坡頂受震反應，使坡頂位移增量大於坡面位移增量。(3)若坡角固定，改變坡高時，將放大邊坡受震反應，隨著坡高增加，邊坡位移量及位移增量隨之增加。(4)在邊坡頂緣及趾緣建置建物進行測試可知，在坡趾地面上加置建物，受震時對邊坡及建物的影響不大；但坡頂地面上之建物退縮距離小於10m時，明顯影響邊坡及建物受震行為。(5)建物的加重、加寬或降低樓層高度，均有助於減緩建物於受震時的反應，降低建物位移量的產生。(6)將邊坡進行挖除設置人工擋土設施時，將導致坡頂及擋土設施頂端位移量明顯增加；坡面位移則反而較原邊坡為低。(7)在人工邊坡頂緣後方加設建物，受震時，擋土設施牆頂為最大位移發生處，在人工邊坡頂緣加置建物，將增加邊坡與擋土設施位移及危險性。(8)擋土設施高度增加時，將放大其受震反應，可知擋土設施高度的增加，首先促使擋土牆頂產生受震反應放大現象。(9)當固定挖方，改變挖方位置時，擋土設施及開挖位置距坡頂越遠，將有助於受震時擋土設施及坡頂的穩定。

關鍵字

PLAXIS ； 建物互制 ； 人工邊坡 ； 邊坡受震行為

並列摘要

Slope stability problems have been studied considerably in the past years. Relevant design codes and specifications were established based on the learning. In engineering practice, more people use FDM or FEM analysis while the physical modeling becomes more attractive for particular research studies. In this paper, 2D FEM analysis was conducted using computer program PLAXIS. Numerical examples of a homogeneous earth slope (10m height and 30o inclination) were studied extensively for the design earthquake acceleration (0.29g) under a return period of 475 years in Taipei. Considering the geographic and geological conditions of the local seismic stations and with the past significant earthquakes into the measurement, the acceleration time histories recorded at a particular seismic station located at Chungho District in New Taipei City were calibrated to target PGA for the inputs. Varying the PGA, the soil parameters and the slope geometry, the maximum horizontal displacements of the slope were computed and compared to make the observations and discussions. Slopes with and without the building on the top or at the toe were studied to see their interactions. In general, it is found that local Design Specification on minimum distance of the building from a slope is appropriate for the seismic concerns. Potential defects will be discussed with more elaborations.
The observation are summarized as follows：(1) Before the slope collapsed due the earthquake, the maximum displacement will occur on the slope surface where the crest displacement is also found critical. (2) As the slope angle increases, the maximum displacement of the slope will move to the crest. (3) By changing the height of the slope with the same inclination angle, the displacement will increase. (4) A building around the toe will not affect the response very much, however a building on the crest will affect significantly the response especially within a certain distance, say 10m. (5) By increasing the weight and width of the building or reducing the height will reduce the building responses. (6) An excavation on the slope will make some amplification for the slope on top of the excavation, however the rest parts of the slope are de-amplified. (7) If a building is built behind the man-made (say retaining wall exist) slope, the construction will enlarge the slope displacements. (8) The height of excavation or the retaining wall is important, its increase will make the slope responses worse especially for slope on top of the excavation. (9) With the same amount of soils in the excavations, the lower the excavation is, the smaller the response will be; which indicates that when making the land developments on the sloping ground, the higher the location is, the more attentions must be paid.

並列關鍵字

PLAXIS ； Slopes with Buildings ； Man-made Slopes ； Seismic Behaviors

參考文獻

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