• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.824-827
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• 2006

The Prefabricated Vertical Drains (PVDs) method is one of the most widely used techniques to accelerate the consolidation process in-situ and hence increase its bearing capacity. In this paper, the degree of consolidation incorporated with PVDs was evaluated in O construction work site which composed with dredged soil. O Program PVD(Version 2.3) which developed by Asian Institute of Technology was used. The purpose of this analysis is efficiently to estimate the degree of consolidation by analyzing the surface settlement with time, and drainage at initial stage and final stage by using design-parameter which based on the in-situ tests and laboratory tests. This result can be compared with analysis of the degree of consolidation using Program PVD(Version 2.3) and the field observed data in the future studies.

• Structural Engineering and Mechanics
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• 제82권5호
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• pp.557-569
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• 2022

The retrofit of existing structures in high seismic zones is a crucial issue in the earthquake engineering field. The interest of the research community is particularly high for the structures that do not respect current seismic codes and present structural deficiencies such as poor detailing and lack of capacity design provisions. A reinforced concrete (RC) school building is used as case study to show the influence of different knowledge levels on the seismic retrofitting cost assessment. The safety assessment of the case study building highlights deficiencies under both vertical and seismic loads. By considering all the possible knowledge levels defined by the Italian such as by the European codes in order to derive the mechanical properties of the school building constitutive materials, the retrofit operations are designed to achieve different seismic safety thresholds. The retrofit structural costs are calculated and summed up to the costs for in-situ in tests. The paper shows how for the case study building the major costs spent for a large number of in-situ tests allows to save a consistent amount of money for retrofit operations. The hypothesis of demolition and reconstruction of the building is also compared in terms of costs with all the analyzed retrofit options.

• Geomechanics and Engineering
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• 제33권5호
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• pp.453-462
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• 2023

Intermediate Geomaterials (IGMs) are natural formation materials that exhibit the engineering behavior (strength and compressibility) between soils and rocks. The engineering behavior of such material is highly unpredictable as the IGMs are stiffer than soils and weaker/softer than rocks. Further, the characterization of such material needs exposure to both soil and rock mechanics. In most conventional designs of geotechnical structures, the engineering properties of the IGMs are either aligned with soils or rocks, and this assumption may end up either in an over-conservative design or under-conservative design. Hence, many researchers have attempted to evaluate its actual engineering properties through laboratory tests. However, the test results are partially reliable due to the poor core recovery of IGMs and the possible sample disturbance. Subsequently, in-situ tests have been used in recent years to evaluate the engineering properties of IGMs. However, the respective in-situ test finds its limitations while exploring IGMs with different geological formations at deeper depths with the constraints of sampling. Standard Penetration Test (SPT) is the strength-based index test that is often used to explore IGMs. Moreover, it was also observed that the coefficient of variation of the design parameters (which represents the uncertainties in the design parameters) of IGMs is relatively high, and also the studies on the probabilistic characterization of IGMs are limited compared with soils and rocks. With this perspective, the present article reviews the laboratory and in-situ tests used to characterize the IGMs and explores the shear strength variation based on their geological origin.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.196.1-196.1
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• 2011

In this study, a test bed was constructed in order to evaluate thermal efficiency of the energy pile which carries out combined roles of a structural foundation and of a heat exchanger. The energy pile in this study is designed as a large-diameter drilled shaft equipped with the heat exchange pipes which configures a W-shape and an S-shape. The drilled shaft reached to the depth of 60 m whilst the heat exchange pipes were installed to about 30 m deep from the ground surface. The W-shaped and S-shaped heat exchange pipes were installed in the opposite sections of the same drilled shaft. In-situ thermal response tests were performed for both the shapes of heat exchange pipes. To avoid underestimating the thermal performance due to hydration heat of concrete inside the drilled shaft, the in-situ thermal response tests for the energy pile were performed after four weeks since the installation of the energy pile.

• 설비공학논문집
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• 제17권2호
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• pp.173-182
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• 2005

The Performance of U-tube ground heat exchanger for geothermal heat Pump systems depends on the thermal properties of the soil, as well as grout or backfill materials in the borehole. In-situ tests provide a means of estimating some of these properties. In this study, in-situ thermal response tests were completed on two vertical boreholes, 130 m deep with 62 mm diameter high density polyethylene U-tubes. The tests were conducted by adding a monitored amount of heat to water over a $17\~18$ hour period for each vertical boreholes. By monitoring the water temperatures entering and exiting the loop and heat load, overall thermal conductivity values of grout/soil formation were determined. Two parameter estimation models for evaluation of thermal response test data were compared when applied on the same temperature response data. One model is based on line-source theory and the other is a numerical one-dimensional finite difference model. The average thermal conductivity deviation between measured data and these models is of the magnitude $1\%$ to $5\%$.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.619-626
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• 2002

In this study, a correlation among pressure, time and quantity of injection was organized from the laboratory tests, which were executed many times representing in-situ soil conditions carefully and then it would be applied to the in-situ soil injection simulator which will be developed for optimal injection into the ground. The sort of sample soils were both sand(A specimen) and silty sand(B specimen). Injection tests were gone into operation by compaction state, injection velocity and the depth individually. In the ground improved with permeation Infection, the relation among injection pressure of the same depth, the injected quantities and time were systematic by the depth. By defining the limit range of injection pressure and quantity about the variety of a linear equation obtained from lining each of their trend, the application of laboratory injection monitoring program and the data to evaluate its realization were produced. In the ground improved with root type injection, the relation between injection pressure and the injected quantities was irregular because fracture state occurred quickly.

• Geomechanics and Engineering
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• 제5권4호
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• pp.313-329
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• 2013

Vetiver grass (Vetiveria zizanioides) is being effectively used in many countries to protect embankment and slopes for their characteristics of having long and strong roots. In this paper, in-situ shear tests of the ground with the vetiver roots have been conducted to investigate the stabilization properties corresponding to the embankment slopes. Numerical analyses have also been performed with the finite element method using elastoplastic subloading $t_{ij}$ model, which can simulate typical soil behavior. It is revealed from field tests that the shear strength of vetiver rooted soil matrix is higher than that of the unreinforced soil. The reinforced soil with vetiver root also shows ductile behavior. The numerical analyses capture well the results of the in-situ shear tests. Effectiveness of vetiver root in geotechnical structures-strip foundation and embankment slope has been evaluated by finite element analyses. It is found that the reinforcement with vetiver root enhances the bearing capacities of the grounds and stabilizes the embankment slopes.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.215-222
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• 2001

Uncertainty study of shear strength characteristics of the marine clays was carried out based ell In-situ tests and laboratory tests on tile south-east coastal region of the Korean peninsula. Theoretical analyses were studied using both tile spherical cavity expansion theory in finite soil mass and the strain path method to determine tile cone factor using the undrained shear strengths obtained by in-situ tests, and the empirical methods in accordance with the ultimate resistance theory were also discussed. Analysis show that the empirical methods suggest more reasonable value than that of theoretical methods in terms of comparing the cone factor estimated using linear regression and frequency distribution analyses. The cone factors obtained by the empirical methods are 18, 15, and 6 respectively, from the results of total cone resistance, effective cone resistance, and excess porewater cone resistance method, and the estimated were similar to those of previous researcher's.

• Smart Structures and Systems
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• 제4권1호
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• pp.1-17
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• 2008

This study proposes a conceptual framework of in-situ vibration tests and analyses for quality appraisal of non-slender, cast-in-place piles with irregular cross-section configuration. It evaluates a frequency index from vibration recordings to a series of impulse loadings that is related to total soil-resistance forces around a pile, so as to assess if the pile achieves the design requirement in terms of bearing capacity. In particular, in-situ pile-vibration tests in sequential are carried out, in which dropping a weight from different heights generates series impulse loadings with low-to-high amplitudes. The high-amplitude impulse is designed in way that the load will generate equivalent static load that is equal to or larger than the designed bearing capacity of the pile. This study then uses empirical mode decomposition and Hilbert spectral analysis for processing the nonstationary, short-period recordings, so as to single out with accuracy the frequency index. Comparison of the frequency indices identified from the recordings to the series loadings with the design-based one would tell if the total soil resistance force remains linear or nonlinear and subsequently for the quality appraisal of the pile. As an example, this study investigates six data sets collected from the in-situ tests of two piles in Taipu water pump project, Jiangshu Province of China. It concludes that the two piles have the actual axial load capacity higher than the designed bearing capacity. The true bearing capacity of the piles under investigation can be estimated with accuracy if the amplitude of impact loadings is further increased and the analyses are calibrated with the static testing results.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1073-1076
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• 2010

Shallow foundations of various columns such as traffic signs, CCTVs, traffic lights, street lights, steel telephone poles and so on are made by cast-in-situ concrete method. However, typical cast-in-situ method has many problems because of the long duration of construction, occupation of sidewalks and low strength of the concrete after curing. In order to solve the problems, field load tests for the prefabricated DSF foundation made by combination of column and foundation was conducted to know load-deformation behavior by torsional tests.