礫石土層水平雙環塞灌漿地盤改良之案例研究

Case study of Horizontal Double Packer Grouting in Gravelly Soils

黃昱銨(Yu-An Huang)

指導教授 ： 方永壽

國立交通大學/工學院/土木工程系所/碩士(2012年)

https://doi.org/10.6842/NCTU.2012.01001

摘要

本論文主題為高鐵桃園站與機場捷運系統A18車站間地下聯絡通道之地盤改良案例研究。本案例所使用之地盤改良工法為水平式雙環塞低壓灌漿工法，於回填礫石土中施灌水泥皂土漿(CB漿)及超微粒水泥漿液(UFC漿液)。除討論注入施工方法外，本研究根據施工單位所提供之監測資料，觀察施工造成之地盤變位。地盤改良工程結束後，研究團隊於隧道開挖期間，以相機記錄各個開挖斷面上的漿脈分佈狀況。依據所拍得的斷面照片，以小區域(單一注入孔周圍)、大區域(兩個或多個注入孔)，對CB漿脈及超微粒水泥漿脈的形狀進行探討，並歸納出水平式雙環塞灌漿在夯實礫石土中之改良機制，獲得以下各項結論。
1、 開挖斷面上的漿脈呈現水平狀居多。其中CB漿液在土層中的流動區域較超微粒水泥漿廣。因CB漿在施灌時，礫石土層中的孔隙內只有水及空氣的存在，因此灌漿時CB漿便會在土層中朝四面流動填補孔隙。
2、 當超微粒水泥灌入地層時，由於土壤中的孔隙已被CB漿所填滿，因此UFC灌漿壓力必須較灌注CB漿液注入壓力為高，才可以順利將超微粒水泥漿灌入地層中。因此，超微粒水泥除了填補地層中更小的孔隙外，也會在CB漿及土壤中形成水力劈裂。UFC漿脈在斷面上的厚度明顯較CB漿脈的厚度為薄。
3、 漿液自灌漿孔灌出後，在來自左右兩邊的壓力σh的作用下，漿液向上劈裂，在受到上一排灌漿形成上側堅實改良土的邊界束制時，漿液轉向水平方向發展，形成蕈狀型漿脈。若開挖面與注入孔位置錯開，在開挖斷面上看不到漿脈與灌漿孔間的連結，形成一無梗蕈狀型漿脈。
4、 地盤內之垂直應力為σv，填土之夯實造成地盤內水平土壓力增加，假設水平灌漿孔周圍水平向土壓力增大並大於垂直向壓力，當灌漿壓力p大於垂直向壓力σv時，依水力破裂理論，注入漿液向灌漿孔兩側水平劈裂。

關鍵字

地盤改良 ； 礫石土 ； 水平式 ； 雙環塞灌漿 ； 水力破裂 ； CB漿 ； 超微粒水泥漿

並列摘要

This thesis is a case study of the ground improvement for the tunneling of a cross-passage between the (HSR) Taoyuan station and the A18 station of the Airport mass rapid transit MRT system. The horizontal double-packer grouting method was conducted in the compacted gravelly fill. The injected grout included cement-bentonite (CB) grout and ultra-fine cement (UFC) grout. Based on the field monitored data, grout movements due to grouting and tunnel excavation were investigated. During the tunnel excavation, the grout permeation and fracture in the ground at specific sections, near different grouting holes, were observed and recorded. Based on the pictures taken, the flow of CB grout and UFC grout near a grout hole, between two holes, and among several holes were carefully studied. Based on thesis data, several typical model of grout flow and its mechanism were established, and the following conclusions were made.
1、 During the injection of CB grout, the void occupied by air and water in the compacted gravelly soil was replaced by the compressed CB grout. The CB grout was used to fill the voids in the ground near the injection pipe.
2、 After the CB grout injection, the voids in the ground were filled with CB grout. The grouting pressure for UFC grouting was higher than that for CB grouting. The UFC grout was used to fill the ultra-fine voids, the hydraulic fracture of the UFC grout in the grout can be observed.
3、 After the grout was pushed out of the injection hole, the smaller horizontal stress σh (assuming σh < σv) acts in the horizontal direction, and a vertical fracture could develops near the injection hole. Under the boundary restrain of its grouted stiff layer, the grout seeps in horizontal direction, and a mushroom-shaped grout pattern was formed.
4、 Assuming the horizontal stress σh in the compacted gravelly soil, was greater than the vertical stresses σv, if the grouting pressure p was greater than σh, the injected grout would cause hydraulic fracture in the horizontal direction.

Keyword: Ground improvement, Gravelly soil, Horizontal, Double packer, CB grout, UFC grout, hydraulic fracture

並列關鍵字

Ground improvement ； Gravelly soil ； Horizontal ； Double packer ； hydraulic fracture ； CB grout ； UFC grout

參考文獻

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