In order to make efficiency use of the congested land in Taiwan, the current trend is towards deep depth of excavation or shield tunnel. The super-jet grouting methods have been introduced since the traditional jet-grouting method is not useful enough for grouting depth over 40m. This paper introduces the difference between several theories of super-jet grouting and its limits, moreover, the key points in design and construction are discussed in the paper. The experimental methods of checking construction quality and the problem during judging will also be presented for reference.
An in-situ test program on double tube jet grouting was carried out at LuZhou depot, Taipei MRT by four local contractors. Purpose of the test program was to validate the diameters and integrity of the jet grout piles. Soil condition at the test site consists of medium stiff silty clay and medium dense silty sand. Jet grouting was conducted within specified layers (
This paper discussed results of CJG and X-Jet triple tube jet grouting at a construction site in Taipei basin. Ground between GL.-19m and GL.-39m was jet grouted. Test piles using bentonite slurry as the grouting fluid was constructed first, and ultrasonic soundings were carried out to verify the diameter of test piles. The results of ultrasonic sounding were used as a design basis for the layout of production piles. After completion of the production piles, cored samples were taken at the overlapping area of adjoining piles. Careful examination on the cored samples showed that quality of the improved body was no where close to the design requirements, though a conservative approach had been adopted in designing the diameter and layout of jet grout piles. It is advised that this finding should not be overlooked by the design engineers, or the safety of construction may be in jeopardy.
In this study, a basement excavation case in Taipei using the JMM jet grouting technique was investigated. Besides regular instrumentation, in-situ and laboratory tests were also conducted both before and after grouting to investigate the effects of jet mixing on the adjacent soils and diaphragm wall displacement. Testing results showed that the soil between the jet grout piles exhibits brittle behavior and slight strength increase. The monitoring results showed that (1) jet grouting would induce significant outward diaphragm wall displacement, and this wall displacement would rebound after some elapsed time, with a recovery ratio of 18%~22%.；(2) Jet grouting had tremendous impact on the diaphragm wall displacement during the subsequent excavation, the displacement profile would gradually move from the unexcavated side toward the excavated side； (3) Soils adjacent to the grouting borehole exhibited large displacement, and the maximum lateral soil displacement recorded adjacent to the jet-mixed piles was about 6.2cm.；(4) During jet grouting, the excess pore water pressure of adjacent soils increased significantly, the closer the larger with a maximum value of about 1.5 times the in-situ pore water pressure.
Gravel formations comprise compound materials. Their diverse characteristics depending upon content, distribution and nature of the composing gravel and fine-grained materials, together with their high permeability, make it more complicated to apply grouting in gravel formations than in regular soil or rock formations. This paper provides a preliminary introduction to the theoretical background, selection of grout materials and construction parameters, and construction management of sleeve grouting in gravel formations. A case of grouting in a launch shaft of a shield machine in Chung Li area is also studied to verify the applicability of the aforementioned permeation theory and construction parameters.
The excavation depth of O8 station is up to 34m in Taipei MRT Hsing-Chung line Lot CK570G. The bottom of the excavation is located in Songshan formation II. The high water pressure of Jingmei gravel formation must be leveled down to prevent blow-in in foundation layers. Diaphragm walls of 1.8m thick and 58m deep were used. In addition, a 5m thick artificial confining bed above the tip of the diaphragm wall was constructed to reduce the quantity of drainage. All assignments of excavation have been completed successfully. This paper introduces the planning, construction method, construction procedure, and effectiveness of the confining bed for future reference of similar projects.
High pressure or chemical grouting is commonly adopted as an auxiliary method during the excavation of crosspassage of MRT. This paper presents the details of double packer method, the best method of chemical grouting, used as an auxiliary method during the excavation of crosspassage of Contract CH221 of Taipei MRT. This will be a reference for the design and construction of the similar project in the future.
This paper reports the ground improvement and excavation of a cross passage and a drainage sump between two shield tunnels for the construction of Tu-chen Line of Taipei Rapid Transit Systems. Jet grouting was conducted for soils around the cross passage before the tunneling of the shield machine. Leakage tests were conducted to detect the cracks in the JSG soilcrete, and chemical grouting was conducted from the shield tunnel to fill the cracks. Compressed-air method was selected as an auxiliary method to depress the groundwater pressure and prevent water inflow at the face of excavation. The construction of cross passage and drainage sump was successfully completed. It is concluded that the subsurface conditions encountered at a great depth might be quite complicated. The geotechnical engineer should never overestimate the watertight characteristics of the soilcrete body formed around the cross passage by jet grouting and chemical grouting. Under the threat of high water pressure, the contractor is suggested to bear the multiple lines of defense concept to keep the excavation work on the safe side.
In geotechnical underground engineering, such as deep excavation, shield tunneling construction, is generally considered as a high risk operation. It is very important stage to identify geology improving among these works. In traditional execution, they use destructive method, boring and water test, to verify the effect of geology improving. But they usually present the regional condition only, can not show the whole underground condition. Because of the improving soil or block have high resistivity characteristic and high water content soft soil have low resistivity. In this paper, we use developed non-destructive geophysical exploration, Electrical Resistivity Imagine Profile (RIP), to identify the quality of geology improving and predict the risk in underground engineering. We will introduce two cases and the results show that the RIP can clearly present the condition of underground anomaly. By doing this, we improve this method from 2D to 3D tomography. The outcome shows the traditional geological survey has been improved to a better accuracy in engineering problem solving.