• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.45-52
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• 2010

One of the ways to minimize damage by a slope collapse is to set up preventive measures in advance by measuring displacements in a slope and predicting a collapse. There have been many different technologies developed to predict a collapse with diverse measuring equipment. Especially recently, attempts have been made to utilize terrestrial LiDAR, a high-tech imaging equipment to measure displacements on a scope. Terrestrial LiDAR generates three-dimensional information about an object with millimeter-level accuracy from hundreds of meters away and has been used in an array of fields including restoration of cultural assets, three-dimensional modeling, and making of topographic maps. In recent years, it has been used to measure displacements in structure as well. This study monitored displacements in slopes of high collapse risk with terrestrial LiDAR. As a result, it was able to confirm the applicability of terrestrial LiDAR to the field, and proposed monitoring methods.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.223-233
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• 2003

Sand compaction pile (SCP) is one of the ground improvement techniques which are being used for not only accelerating consolidation but also increasing bearing capacity of loose sands or soft clay grounds. In this study, laboratory model tests and 3-D finite element analyses were performed to investigate the interaction between sand compaction piles and surrounding soft soils. Based on the results obtained, as the area replacement ratio increases, the stress concentration ratio increases at the pile point, the settlement decreases, and the relative displacement between column and soil also decreases. It is also found that numerical study is illustrated by good comparison with model test results, and the numerical analysis revealed slip effects which could not be specifically identified in the model tests.

• Explosives and Blasting
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• v.37 no.4
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• pp.1-9
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• 2019

In this study the applicability of a Digital Image Correlation (DIC) method was investigated by measuring the displacement and vibration of rock pillar due to underground mining blasting. When combined with a high speed photography technology, the DIC method provides an excellent photographic image processing ability that can be used to convert the evolving full-field surface properties of structures to 2D or 3D set of coordinate values. The measured coordinate sets are then used to calculate the displacement, strain, and velocity of the target structure. This technique is widely used in science and engineering, and continuously finds its new application areas. In this study, the DIC system and the conventional seismograph were compared for their ability to measure the displacement and vibration produced by blasting. In the field test both methods showed similar results. Thus, it is concluded that the DIC method is feasible to measure the ground displacements and vibrations from blasting.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.4
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• pp.329-340
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• 2010

Mechanical behavior of underground cavity construction such as tunnel is very difficult to estimate due to complexity and uncertainty of ground. Prediction of behavior according to excavation of tunnel mainly uses method utilized of model test or numerical analysis. But scale model test is difficult to reappear field condition, numerical analysis is also very hard to seek choice of suitable constituent model and input data. To solve this problem, this paper forecasted the deformation of tunnel that applied to information of crown settlement and convergence, RMR in weathered granite by using the regression analysis. The result of the analysis shows that the crown settlement according to excavation occurs approximately 70~80% of total displacements within about 20 days. As a result of the prediction of crown settlement and convergence, an exponential function becomes more accurate at measurements than an algebraic function. Also this paper got a correlation in comparison of RMR and displacements of 6 sections.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6C
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• pp.407-419
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• 2006

Situations where support is provided solely in shaft resistance of drilled shafts are where the base of the drilled hole cannot be cleaned so that it is uncertain that any end bearing support will be developed. Alternatively, where sound bed rock underlies low strength overburden material, it may be possible to achieve the required support in end bearing on the rock only, and assume that no support is developed in the overburden. However, where the drilled shaft is drilled some depth into sound rock, a combination of side wall resistance and end bearing can be assumed. Both theoretical and field studies of the performance of rock socketed drilled shafts show that the major portion of applied load is usually carried in side wall resistance. Normal stress at the rock-concrete interface is induced by two mechanisms. First, application of a compressive load on the top of the pile results in elastic dilation of the concrete, and second, shear displacement at the rough surface of the drilled hole results in mechanical dilation of the interface. If the stiffness of the material surrounding the socket with respect to normal displacement is constant, then the normal stress will increase with increasing applied load, and there will be a corresponding increase in the shear strength. In this study, the numerical analyses are carried out to investigate the behavioral characteristics of side of rock socketed drilled shafts. The cause of non-linear head load-settlement relationship and failure mechanism at side are also investigated properly and the design charts are suggested and verified for the leading to greater efficiency and reliability in the pile design.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.2
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• pp.129-137
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• 2008

This paper intends to develop an assesment technique for the rapid and quantitative evaluation of tunnel safety during tunnel excavation by using displacement measurements. Control criteria for the field measurements are provided at tunnel construction sites in Korea and other countries. However, it was known that the criteria were not clear and varied depending on the construction sites. In order to make a reasonable support for guidelines, critical strain concept is introduced in this study. And the engineering meanings of the critical strain concept are investigated precisely. In order to do this, at first, the engineering meanings of the original concept from the previous researchers was investigated theoretically for the evaluation of tunnel safely. Subsequently displacement data were obtained by using the commercial program, then the evaluation of tunnel safely was conducted with the view point of previous researches. Additionally, strains are determined from the feedback analyses program by inputting measured displacements that were obtained from the commercial program, then the evaluation of tunnel safety was discussed with the critical strain concept. Consequently it can be concluded that the evaluation of tunnel safety can be determined quantitatively and rapidly in the field by introducing the critical strain concept.

• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.29-36
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• 2007

The control and prediction of surface settlement, gradient and ground displacement are the main factors in urban tunnel construction. This paper carried out the estimation and prediction of ground behavior around tunnel due to excavation using computational method and case study in detail for the analysis of deformation behavior in urban NATM tunnel. Computational method was performed by FLAC-2D with strain softening model and elastic plastic model. Field measurements of surface subsidence and ground displacement were adopted to monitor the ground behavior resulting from the tunneling and these values were applied to modify tunnel design parameters on construction.

• Geotechnical Engineering
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• v.11 no.2
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• pp.5-18
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• 1995

A Compaction-induced lateral earth pressure was measured for a reversed-T type retaining wall of 4m high for three months. As a result of in-situ measurements, the lateral earth pressure fluctuated sharply with time after backfill, which was closely dependent upon the displacement of the retaining wall. The measured results showed big discrepancy with theoretical predictions made by existing theories, which are applicable to rigid wall. However, the in -situ data twas compared relatively well with those obtained by the finite element method. Analysis showed that the discrepancy may be caused by the displacement of the retaining wall during the compaction of the backfill.

• Journal of the Korean Geotechnical Society
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• v.26 no.11
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• pp.39-46
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• 2010

The magnitude of the lateral resistance that resists the lateral movement of the pile is controlled by the amount of the pile movement and the strength and stiffness of soil. In this paper, we proposed an equation which produces the lateral resistance of the laterally loaded single pile using the strain wedge model of the soil deformation. The results of this equation is compared with results of model test, field test, p-y curve and other methods. It is found that the result of proposed equation is smaller than the result of model test. The results of loading test considerably coincide with those of proposed equation; however, a few of deviations are generated as the displacement of pile head increases. Moreover, coincidences exist between the results of the proposed equation and those of finite difference method.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.53-61
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• 1999

The safety of gas utilities is intimidated by many causes. Among them, subsidence is a dominant cause to decrease the safety of gas utilities. So it is very important to monitor the displacement of subsidence. The purpose of this study is to on-line monitor the subsidence of gas utilities using Static GPS(Global Positioning System)technique. Static GPS technique, which is one of various GPS techniques and originally applied to monitor the crustal activity, was applied for two gas station in Korea Gas Corporation. Prior to applying this technique to the field, i.e, gas station, a preliminary test was peformed to confirm the accuracy of this technique. As a result, it was proved that this technique can measure the displacement of gas utilities three dimensionally by sub-millimeter. After getting confirmation of GPS technique, we applied this technique for two gas stations and monitored the amount of subsidence during 5 months. As a result of field test, we can conclude that the gas stations was subsiding several millimeters in a year.