英文篇名
USE OF BLASTING DENSIFICATION METHOD IN COMPACTING SANDY SOILS
作者
鄭富書、余昌學、趙基盛、陳福勝、何泰源
關鍵字
地盤改良、炸震夯實法、砂土
摘要
軟弱土層之各種改良方法中,炸震夯實法係藉由引爆深埋土中之炸藥、造成大規模之土壤液化,隨後土壤顆粒由於自重而重新堆置,形成緊密之結構而達改良之目的。因此,對於深層、大範圍之砂性土壤改良作業而言,本法之施作速度快、毋需特殊器具,可供工程界作為夯實方法之新選擇。
本文就炸震夯實之發展歷史、基本原理與作用機制、夯實成效影響因素與工程設計實務作一系統性介紹。此外,室內模型試驗探討土壤變形組態與全尺度之現地試驗結果亦列於本文中。試驗結果發現,在乾燥土層中開炸後,炸源周圍土體形成之空洞陷落,造成地表沉陷;若於不飽和土體中開炸,炸後空洞維持不崩坍。現地試驗結果顯示,此法之成果顯著,造成地表達85公分之沉陷,且SPT及CPT貫入阻抗亦提昇;改良深度達全鑽孔深度,約20公尺左右。同時,實驗結果亦顯示開炸形態與炸藥引爆方式對炸後孔隙水壓分佈及是否引起大規模之土壤液化有關而影響夯實成效甚鉅。
英文摘要
Among the methods for improving the strength of weak soils, Blasting Densification method (BDM) is characterized with fastness in constructional time and low-cost, compared to other methods. As BDM is conducted by detonating explosives in a borehole, this method enables efficient compaction of sandy soil in a great depth or any depths desired.
The historical development of BDM, the mechanism and the design concepts of BDM are presented with focus on elucidating the key factors influencing the effectiveness of compaction. Meanwhile, model tests conducted in laboratory and full-scaled in-situ tests have been conducted to further identify the deformation of the soil body after the blasting and to access the validity of adopting BDM in Taiwan. Model test results indicate that a cavity was formed at the moment of explosion, followed by collapsing of the cavity, provided sufficient overburden exists. Field test results reveal that the layout of the blasting sequence and detonation delay play an important role in inducing liquefaction of the loose stratum, which in turn results in a more compacted structure of particles and thus improves the strength of the soil.