• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.122-128
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• 2003

Rock bolts are widely used as a supplementary roof support system in hard-rock mining since a long time. Since the performance of fully grouted passive bolts depends on bond strength, in the present investigation extensive laboratory pull-out as well as push-out tests were conducted varying the bolt diameter, length and cement-water mixing ratios of grout. The load-displacement curves were developed and were verified with the numerical results obtained from finite element analysis using ALGOR software. Numerical models were validated for push-out tests and a detailed analysis was carried out to know the displacement, stress, strain distribution along the bolt.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.453-460
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• 2005

Sodium silicate - the usual portland cement which accomplishes a cement pouring reconsideration main stream and sodium silicate(No.3) after reacting sodium silicate(No.3) with the reaction sodium silicate where oxidation natrium which is included does not react with the cement receiving stiffening water it will burn together on underwater and to become the durability lacks pouring it is recognized. From the hazard which improves an advantage it used the additive which relates in congealing and stiffening of the portland cement and sodium tripolyphosphate(STPP) addition hour initial material age(72 hours at once) which does to be revealed the at high-in-tensity is discovered while accomplishing. The effect of additives on the reactions of sodium silicate solution and cement suspesion was investigated by various physical and chemical tests, such as Si-NMR, XRD, SEM uniaxial compression test. The additives were STPP(sodium tripolyphosphate), EDTA, SUGAR. The compressive strength of sodium silicate(No.3) - cement grout with additives was about $1.5{\sim}10$ times higher than that without additive in early age(72 hours).

• Journal of the Korean GEO-environmental Society
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• v.16 no.8
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• pp.5-12
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• 2015

In this study, buoyancy-resistance permanent anchor was considered to prevent uplift pressure of a building structure. However, this test was failed to put anchor body in the boring hole because of the rapid outflow of ground water and coefficient of permeability. In addition, the hole where the anchor body was forcefully inserted constantly flew the sea water and cement. And it was found that anchor was not settled in the ground. In order to solve this problem, jet grouting method was applied to block the ground water and the single grouted column method was chosen to install the buoyancy-resistance permanent anchor. In this paper, the single grouted column method was applied with the general jet grouting methods and grout material was fixed by 3-field tests. These tests confirmed the effect of permeability and ground improvement with field permeability test by core sampling, Standard Penetration Test (SPT) and unconfined compression test. Confirming the stability of the buoyancy-resistance permanent anchor with installation and tension test, application of the single grouted column method in the volcanic clastic zones was verified.

• The Journal of Engineering Geology
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• v.12 no.1
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• pp.63-73
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• 2002

To evaluate reinforced region of dike by cement grouting, we investigated both the electrical resistivity and the strength of cement grout having various water-cement ratio with curing time. These investigation results showed that the electric conductivity of grout is much higher than that of water and that the apparent resistivity of grouted region is much lower than that of unoccupied region by grout. It was founded that electrical resistivity survey might be quite effective to detect grout region in dike. As the results of electrical resistivity sounding at three dikes, apparent resistivities after grouting showed several tens to several hundreds of ohm-m which were lower than those of pre-grouting and showed stabilizing trend with curing time. From these results, we could estimate that this behavior of apparent resistivity is due to increasing strength with curing time.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.154-163
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• 2009

The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement-based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed-form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement-based grout in the soil matrix. The closed-form solution relevant to a particular spherical flow was modified by a step-wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot-scale chamber injection tests was performed to verify that the developed step-wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step-wise numerical calculation. Based on the filtration phenomenon, a new groutability criterion of cement-based grout in a porous medium was proposed, which might facilitate a new insight in the design of the grouting process.

• Journal of the Korean GEO-environmental Society
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• v.10 no.2
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• pp.51-59
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• 2009

This study is based on field data obtained from rock grouting such as RQD value, Unit cement grout volume, Lugeon value(Lu), and Maximum grout pressure in four different dam sites. The relationship were analyzed and compared as follow. The cut-off effect after rock grouting in dam-foundation which are mostly consist of metamorphic rock is better than that of Sedimentary rock. And the impermeable effect after consolidation grouting is more efficiency than the impermeable effect after curtain grouting. The unit cement grout volume are increased as RQD value is higher in rock mass. But there is no relationship between RQD value and Lugeon value. In the sedimentary rock, which is more permeable than metamorphic rock, Lugeon value (Lu) is a linear function (Lu=0.22Vc) of unit cement grout volume (Vc). Cut-off effect of curtain grouting is less influential at each near holes which are already grouted than that of consolidation grouting. And the behavior characteristics of Lugeon value vs. the unit cement grout volume as the order of installations are almost the same.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1559-1570
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• 2008

A new grouting material named 3S is developed that can be used effectively for reinforcing cut surface of weathered rock in processing of tunneling. The new material is composed of mostly micro slag cement and general Portland cement, but the material is foundered again upto $8,000\;cm^2/g$ of specific area so that it can be easily infiltrated in to the ground. For verifying technical and engineering quality of the material several laboratory tests with specially designed test apparatus were performed including compression tests, infiltration tests and resonant column tests. It was verified that the newly developed grouting material at early age of 1 or 3 days generates 200~1500% higher compressive strength and 400~560% larger elastic modulus than those of the LW(LW-1) or micro-cement(LW-2) grouting materials in the market. In addition, the new 3S grouting material could be so easily infiltrated into the model ground in the lab tests that it produces 4 times larger grouted roots in average compared to the usual water glass type grouting material(LW-1). Thus, it can be said that the newly developed grouting material can effectively prevent inflow water into tunnel compared to LW grouting materials.

• Journal of Soil and Groundwater Environment
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• v.25 no.3
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• pp.43-51
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• 2020

About 90% of groundwater wells in Jeju Island are reported to be under the threat of contamination by infiltration of the surface pollutants. Most of those wells have improperly grouted annulus which is an empty space between the well and the inner casing. As a remedy to this problem, some of the wells were re-grouted by filling the annulus with cement without lifting an inner casing. In order to evaluate whether this method is appropriate for the geological structure of Jeju Island, two wells (W1 and W2) were selected and this method was applied. The water holding capacity did not decrease while the nitrate levels decreased from 16.8 and 20.2 to 6.8 and 13.8 mg/L in W1 and W2, respectively. The higher nitrate level in W2 is deemed to be influenced by the livestock farms located in the upper area of the well. In addition, transmissivity of the vedose zone was higher in W2 than W1, potentially facilitating the transport of nitrate to the groundwater. The overall result of this study suggests re-grouting of wells for the purpose of protecting water quality of goundwater should take into account geological structure of vadose zone as well as appropriate source control of the contaminants.

• Geotechnical Engineering
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• v.13 no.5
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• pp.101-124
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• 1997

The root pile system is insitu soil reinforcement technique that uses a series of reticulately installed micropiles. In terms of mechanical improvement by means of grouted reinform ming elements, the root pile system is similar to the soil nailing system. The main difference between root piles and soil nailing are due to the fact that the reinforcing bars in root piles are normally grouted under high pressure and that the alignments of the reinforcing members differ. Recently, the root pile system has been broadly used to stabilize slopes and retain excavations. The accurate design of the root pile system is, however, a very difficult tass owing to geometric variety and statical indetermination, and to the difficulty in the soilfiles interaction analysis. As a result, moat of the current design methods have been heavily dependent on the experiences and approximate approach. This paper proposes a quasi-three dimensional method of analysis for the root pile system applied to the stabilization of slopes. The proposed methods of analysis include i) a technique to estimate the change in borehole radium as a function of the grout pressure as well as a function of the time when the grout pressure is applied, ii) a technique to evaluate quasi -three dimensional limit-equilibrium stability for sliding, iii) a technique to predict the stability with respect to plastic deformation of the soil between adjacent root piles, and iv) a quasi -three dimensional finite element technique to compute stresses and dis placements of the root pile structure barred on the generalized plane strain condition and composite unit cell concept talon형 with considerations of the group effect and knot effect. By using the proposed technique to estimate the change in borehole radius as a function of the grout pressure as well as a function of the time, the estimations are made and compar ed with the Kleyner 8l Krizek's experimental test results. Also by using the proposed quasi-three dimensional analytical method, analyses have been performed with the aim of pointing out the effects of various factors on the interaction behaviors of the root pile system.

• Geomechanics and Engineering
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• v.32 no.4
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• pp.375-385
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• 2023

There are many joint fissures distributed in the engineering rock mass. In the process of geological history, the underground rock mass undergoes strong geological processes, and undergoes complex geological processes such as fracture breeding, expansion, recementation, and re-expansion. In this paper, the damage-stick-slip process (DSSP), an analysis model used for rock mass failure slip, was established to examine the master control and time-dependent mechanical properties of the new and primary fractures of a multi-fractured rock mass under the action of stress loading. The experimental system for the recemented multi-fractured rock mass was developed to validate the above theory. First, a rock mass failure test was conducted. Then, the failure stress state was kept constant, and the fractured rock mass was grouted and cemented. A secondary loading was applied until the grouted mass reached the intended strength to investigate the bearing capacity of the recemented multi-fractured rock mass, and an acoustic emission (AE) system was used to monitor AE events and the update of damage energy. The results show that the initial fracture angle and direction had a significant effect on the re-failure process of the cement rock mass; Compared with the monitoring results of the acoustic emission (AE) measurements, the master control surface, key blocks and other control factors in the multi-fractured rock mass were obtained; The triangular shaped block in rock mass plays an important role in the stress and displacement change of multi-fracture rock mass and the long fissure and the fractures with close fracture tip are easier to activate, and the position where the longer fractures intersect with the smaller fractures is easier to generate new fractures. The results are of great significance to a multi-block structure, which affects the safety of underground coal mining.