基于原状岩芯的大桥岸坡卸荷带划分

Identification of Unloading Zone of Rock Mass for Bridge Abutments from Undisturbed Rock Core Samples in Deeply Cut River Valley

深切河谷岸坡卸荷带发育,卸荷带范围及性质决定着大桥及墩台位置的选取;平硐勘探耗时长、费用高、安全性差,利用半合式单动双管钻探技术采取原状岩芯样,可快速、经济、安全地对岸坡进行勘探,快速有效地进行岩体结构面及RQD的分析统计,以定性及半定量成果确定卸荷带发育情况及性质,为岸坡稳定性评价奠定基础;在某大桥岸坡勘察中首次采用半合式单动双管钻探采取原状岩芯+整体无损岩芯转移保存技术,进行岸坡卸荷带的原位研究,有效证明了该技术可部分替代平硐勘探,为今后类似大桥岸坡卸荷带快速勘探提供勘察经验。

The unloading zones in the rock mass are frequently encountered in the deeply cut river valleys.The geological properties and limits of these unloading zones might determine the locations the proposed bridge abutments.The conventional exploration drift method has the disadvantage of time consuming,high cost and poor safety.However,a new exploration method,which utilizes a semi-closed single action double tube rock core bit to extract the undisturbed rock cores,can provide a rapid,cost effective and safe method to investigate the river banks.This method can efficiently analysis the structure plane,perform statistical analysis on rock core RQDs and provide qualitative and semi quantitative evaluation results for the unloading zones at both sides of the river banks.This paper presents the exploration results for the proposed Jiangdi River Bridge in Yongren to Dayao Highway Project.In this project,the semi-closed,single action and double tube rock core bit and undisturbed rock core preservation technique were first used in the evaluation of the unlading geologic zone.