This paper presents the application of displacement back analysis for the tunnel engineering in gravel-cobble stratum taking the loosing zone into consideration.
研究了考虑围岩松动圈的位移反分析在卵砾石层隧道工程中的应用。
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C. Vibration strike: it is used in drilling and casing with loosen sand, cobble stone and gravel layer etc.
振动击打：用于松散的砂、卵石、碎石地层的钻进及下套管等。
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Test results show diamond enhanced tungsten carbide composite spherical crown button bits are the ideal bits in drilling cobble and gravel formation.