The design of the chemical grouting is based on the preliminary investigation which includes the surrounding conditions and geotechnical properties. The workability during the construction, fund for the grouting, operation duration, environmental impact and appropriate grouting measures have to be taken into account to achieve the aim of grouting work. Due to the uncertain reason, such as the complication of soil properties and nonuniformity of the improvement, the conventional stability analysis could not serve as the basis for the grouting design which shall be taken the responsibility by the empirical method. So, this paper provides civil engineer with related information and fundamental concept for the grouting design which includes the foll9ws: 1.The applicability of grouting materials and methods 2.The determination of the extent of grouting 3.The estimating amount of the grouting 4.Layout of the grouting holds 5.The methods for grouting test and the evaluation of the grouting effect.
The purposes of compaction grouting include: (a) to densify soils, hence, to reduce subsequent settlements and (b) to lift up structures. This paper, based on the results of a trial carried out for Contract CC275 of the Taipei Mass Rapid Transit Systems, discusses the effects of procedure, surcharge and the slump of grout on the effectiveness of compaction grouting. It has been found that : (a) permanent heave can be achieved in sandy gravels, (b) grout with large slump will not result in hydraulic fracturing, and ( c) surcharge in a small area will not affect the pattern of cone failure, however, ground heave will be reduced locally.
A piperoof underpass construction using soil grouting as the supporting measure for pipe jacking and excavation is discussed herein. Since the soil to be grouted is mainly silty sand, only sodium silicate type solution grout can permeate into the soil. Ordinary cement based suspension grout, even microfine cement based grout, can only fracture into the soil and form the root-type grout intrusoins within the soil. Although the fracture grouting can increase the cohesion of the silty sand, no clear relationship can be established between the decrease in soil permeability and the grout take. Based on the grout intrusions exposed during the excavation stage, it is found that the horizontally layouted grout holes tend togenerate the horizontally distributed grout intrusions. Meanwhile, the layer formation within the grout intrusions, shows that the mixing proportion of the grout is difficult to control when the low pressure-double tube grouting method is used.
Three methods of high pressure jet grouting by using single tube, double tube and triple tube are introduced. A comparison among their grouting principles, working parameters and equipment is made. Recommendation of effective diameters of grouting in sandy soils and clayey soils from Japan differs with the experience of Mainland China. Trial grout study from two sites in Taipei indicate that the diameter of grouted column should be reduced· with depth. Vertical grouting in sandy soils appears to be more effective, while inclined grouting in clayey soils is not promising.
This article presents the relationship among pump characteristics, outflow rate and jetting velocity in jet grouting. The constituents of soilcrete are similar to concrete, however, there exists more uncertainties for the quality control of soilcrete. The major factors which aff ect the quality of soilcrete are presented, as well as the major uncertainties in predicting the insitu soilcrete. To assure the quality of soilerete field trials and sampling are necessary. A case study of field trial to make sure the strength of soilcrete in Tienmu, Taipei is addressed. Both field procedures and sample evaluation are addressed. These can help engineers to choose the pump pressure, lifting speed, rod rotation speed, cement consumption and admixtures for other similar projects.
A test grouting work was carried out in the clay layer in Chungho area where a shield tunnelling work will be constructed. The single tube, double tube and triple tube system were used in this jet grouting test program and the ground movement caused by jet grouting was monitored. The result of this test grouting suggested that the ground movement caused by jet grouting might be affected by soil condition, layout of the grouting columns, grouting methods, groutmg parameters, groutmg sequence and construction quality. There is no certain model can be used to predict the ground movement cause by jet grouting.
This paper applies the cylindrical cavity expansion model to study the failure mechanism induced by jet grouting in cohesive soils. Results of analyses indicate that the cavity pressure for triple tube grouting is less than the pressure which could induce failure. The single and double tube techniques cause higher cavity pressures which may exceed the critical failure pressure. Observations confirm the merits of triple tube technique on heave control and validate the theoretical failure mechanism.
There is a headrace tunnel, 10.5Km long, in NEW TIENLUN HYDROPOWER PROJECT. Its route went through many faults, of which F3 was the lwidest one among them. The excavation and support of F3 were not so difficult as expected, during the initial period, but these works were still ex-ecuted carefully. After 130m inlength had been excavated in this fault zone, the fault zone collapse accident happened unexceptedly, owing to the softening of the fault gorge and its saturation. Through three meetings, the proposal was to revise the route. Then many treatment methods were taken accor-ding to geological condition, namely consolidation grouting in advance, minipipe roof, consolidation grouting after the excavation and support, and drainage. Eventually it took 8 monthes to go through F3 fault zone.