• The Journal of Engineering Geology
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• v.11 no.2
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• pp.163-174
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• 2001

For quantitative evaluation of geotechnical engineering properties such as rippability and diggability, clear interpretation on the subsUJiace velocity structures should be preceded by figuring out top soil, weathered and soft rock layers, shape of basement, fracture zones, geologic boundary and etC. from the seismic refraction data. It is very important to set up suitable field parameters, which are the configuration of profile and its length, spacings of geophones and sources and topographic conditions, for increasing field data Quality. Geophone spacing of 3 to 5m is reconunended in the land slope area of house land development site. In refraction tomography technique, the number of source points should be more than a Cluarter of available channel number of instrument and the subsurface structure interpretation can be decreased the artifact of inversion by topographic effect. Compared with core logging data, it is shown that the velocity range of the soil is less than 700m/s, weathered rock 700~1,200m/s, soft rock 1,200~1,800m/s on the velocity tomogram section. And the upper limit of P-wave velocity for rippability is estimated 1,200 to 1,800m/s in land slope area of gneiss.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.705-713
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• 2016

For the soft ground construction, the factors not considered in the design stage occurs in the construction stage so that they cause the increase of the construction cost due to the structural stability and the design change. The subject of the study is the construction section of the industrial complex access road made in the Ochang region of Chungcheongbuk-do. The study is concerned with selecting the soft ground handling method such as the replacement method using rock debris and the surcharge reflecting the service load as the soft ground handling measure and analyzing the effect of reducing the construction cost with the stability of structures and the reduction of the construction period. The soft ground in the study section consists of sandy and cohesive soil and is 2.4m to 5.5m deep. It is distributed unevenly between the 1.5m to 5.9m stratums under the ground surface. Settlement is not serious, but the future uneven settlement and difference are expected so that the future settlement behavior is estimated by analyzing the site measurement results after the soft ground treatment. Moreover, in consideration of the regional characteristics and economic efficiency, soil with good quality is replaced with rock debris as the replacement material so that 29% of the construction cost is reduced due to the increase of stability and the reduction of duration. If the estimation of the dispersion of the pore water pressure within the dam body and the change of the underground water level and the relation of the actually measured soft ground with consolidation is studied further on the basis of the study, it is expected that the behavior of the soft ground will be correctly estimated in various site conditions.

• The Journal of Engineering Geology
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• v.22 no.3
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• pp.331-341
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• 2012

Granitoid rocks are generally high-quality rock from a geotechnical perspective, because they rarely contain systematic joints or fragmented fault zones. Although the rock type at the Sanhak site is granite, a collapsed slope has a deep soil layer and shows no residual structures such as discontinuities or faults; surface avalanches from this slope can be observed in several places. To study the stability of this slope, we investigated rainfall duration, variation in pore-water pressure, and the factor of safety considering three cases (current cross-section, initial planning cross-section, revised planning cross-section). With increasing duration of rainfall, the groundwater level rises, up to 20 m in height from ground surface. In the initial planning cross-section, safety was secure for rainfall of 2 days duration, but inadequate for rainfall of 4 days duration. In the revised planning cross-section, however, safety factors were secure for rainfall of 4 days duration. Therefore, to ensure permanent stability at the Sanhak site, a slope degree of 1:1.8 should be maintained during cutting.