• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.241-252
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• 2010

This study investigates the application of dilatometer test for evaluating the deformation characteristics of granular soil. $K_D$ is the most sensitive to the stress history among CPT and DMT measurements, and $E_D$ and $q_c$ are observed to be similarly affected by the stress history. The coefficient of at-rest earth pressure($K_0$) is an indirect measure evaluating the stress history of granular soil. A relation using only DMT indices provides appropriate prediction of $K_0$ values. Although penetration of dilatometer inevitably induces the failure of cementation bonds, $E_D$ reflects the deformation characteristics of undamaged cementation relatively well. Therefore, a slightly better prediction of M value for cemented sand is achieved by using $E_D$ rather than $q_c$. Because of the weaker particle strength of calcareous sand compared than quartz sand, the majority of sand particles adjacent to dilatometer probe will be crushed during penetration. The particle crushing will induce the less contraction of the dilatometer membrane during penetration, consequently, the smaller $K_D$ and $E_D$ of calcareous sand.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.309-316
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• 2000

When highly compressible, clayey soil layers lies at a limited depth and large consolidtion settlements are expected as the result of construction, precompression of soil may be used to minimize postconstruction settlement. In this study, we tried to find the possibility about the effect of ground improvement using flat dilatometer at the Inchon International Airport where preloading was installed. Field and laboratory tests were performed for soft ground before and after preloading in order to check the effectiveness of the soft ground improvement and compared with the test results of dilatometer which obtained before and after preloading at the same location Field tests such as flat dilatometer, vane, CPTu tests were performed before and after preloading and undisturbed samples are obtained to carry out laboratory tests. As comparing results, after preloading, unit weight, effective stress, undrained shear strength were increased and we can also check the decrease of consolidation late caused of decrease of void ratio. Furthermore, it is assumed that the possibility on the effect of ground improvement by using the flat dilatometer

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.17-25
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• 2004

The flat dilatometer test (DMT) is a geotechnical tool to estimate in-situ properties of various types of ground materials. The undrained shear strength is known to be the most reliable and useful parameter obtained by DMT. However, the existing relationships which were established for other local deposits depend on the regional geotechnical characteristics. In addition, the flat dilatometer test results have been interpreted using three intermediate indices - material index $(I_D)$, horizontal stress index $(K_D)$, and dilatometer modulus (E$_{D}$) and the undrained shear strength has been estimated merely using the horizontal stress index $(K_D)$. In this paper, the applicability of the flat dilatometer to Korean soft clay deposit has been investigated. Then an artificial neural network was developed to evaluate the undrained shear strength by DMT and the ANN, based on the $p_0, p_1, p_2, {\sigma '}_v$ and porewater pressure. The ANN which adopts the back-propagation algorithm was trained based on the DMT data obtained from Korean soft clay. To investigate the feasibility of ANN model, the prediction results obtained from data which were not used to train the ANN and those obtained from existing relationships were compared.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.365-368
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• 2003

Despite of the simple equipment and operation, DMT has been widely used to obtain various soil parameters and those parameters have been successfully applied to geotechnical design practice. Among them, the estimation of horizontal coefficient of consolidation is so useful that many researchs recently have been carried out. However, simulation of the penetration of the DMT blade is complex due to the inherent difficulty on analyzing a plane strain deformation of the soil around blade. Therefore, empirical and semi-empirical methods that use the theoretical solution developed fur piezocone with some assumptions have been used to estimate the coefficient of consolidation from Dilatometer dissipation test. In this paper, coefficients of consolidation c$\_$h/ which were obtained using equivalent radius that is same area with the DMT blade and optimization technique are compared with those obtained from Oedometer test and other interpretation methods. It was found that a new method used in this study can give more precise horizontal coefficient of consolidation than other methods do.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.677-684
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• 2000

Piezocone test as well as Dilatometer tests are used worldwide to evaluate the engineering properties of clay soils. The common strong point of the two tests is that they can estimate, by the identical test equipment, various properties of soils, which are the unit weight of soils of OCR, K$\sub$o/, undrained shear strength(s$\sub$u/), coefficient of consolidation(c$\sub$h/) and soil classification etc,. A series of the two types of field tests are performed in this study on marine clays with low plasticity at Inchon International Airport construction site to estimate various properties of the soils such as s$\sub$u/, OCR, and c$\sub$h/, which are then compared each other as well as with the results of reference tests. The comparisons show that the way of interpretation is the most critical factor in obtaining confidential results for a certain engineering property for both tests.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.484-491
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• 2008

The purpose of this study is to compare the cementation effect on cone resistance and DMT indices and to evaluate the deformation characteristic of cemented sand using cone resistance and dilatometer modulus. Specimens of various relative densities with three different cementation levels are prepared in a large calibration chamber under different vertical stress levels. Test result shows that the cone resistance and dilatometer modulus underestimate the deformation modulus of cemented sand, since in situ penetration tests such as CPT and DMT damage the cementation bonds during penetration. By regression analysis, the constrained modulus of cemented sand is related with the cone resistance and the dilatometer modulus.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.740-746
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• 2010

Most important characteristics of calcareous sand are the particle angularity and hollow structure. These characteristics lead to the different behavior of calcareous sand compared to siliceous sand. This study performs a series of dilatometer test using calibration chamber, in order to analyze the effect of particle characteristic of calcareous sand on DMT indices. From experimental test, it is observed that the horizontal stress index($K_D$) and dilatometer modulus($E_D$) of calcareous Jeju sand is underestimated compared to siliceous sand. This is because the particle crushing during penetration induces the less contraction of the dilatometer membrane. A slightly smaller influence of particle crushing is reflected in $E_D$ rather than $K_D$, because $P_1$ pressure reflects the deformation characteristics of un-crushed particle relatively well. It is also observed that $K_D$ of Jeju sand is differently influenced by the vertical effective stress compared with that of siliceous sand.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.154-161
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• 2004

The flat dilatometer test(DMT) is a geotechnical tool to estimate in-situ properties of various types of ground materials. The undrained shear strength is known to be the most reliable and useful parameter obtained by DMT. However, the existing relationships which were established for other local deposits depend on the regional geotechnical characteristics. In addition, the flat dilatometer test results have been interpreted using three intermediate indicesmaterial index($I_p$), horizontal stres index($K_p$), and dilatometer modulus($E_p$) and the undrained shear strength is estimated only by using the horizontal stress index($K_D$). In this paper, an artificial neural network was developed to evaluate the undrained shear strength by DMT and the ANN, based on the $p_0,\;p_1,\;p_2,\;{\sigma}'_v_0$, and porewater pressure. The ANN which adopts the back-propagation algorithm was trained based on the DMT data obtained from Korean soft clay. To investigate the feasibility of ANN model, the prediction results obtained from data which were not used to train the ANN and those obtained from existing relationships were compared.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.111-122
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• 2012

Resistivity seismic dilatometer (RSDMT) system is introduced. The resistivity module for obtaining resistivity-depth plot and seismic module for obtaining wave velocity-depth plot are attached to the conventional flat dilatometer testing equipment. To enhance the reliability and repeatability of seismic part in RSDMT, automatic testing system including automatic surface source, PC based data acquisition system and operating program was constructed. To obtain real resistivity value of soil, geometric factor for the array of electrodes in RSDMT was derived empirically. The verification studies for the developed RSDMT system were performed with SPT, CPTu, bender element test and DC resistivity survey. Through one penetration of RSDMT, various soil parameters were obtained and the reliability and repeatability of developed RSDMT system could be checked.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.251-256
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• 2007

The aim of this paper is development of resistivity seismic dilatometer (RSDMT) system. The resistivity module for obtaining apparent resistivity depth plot and seismic module for obtaining shear wave velocity (Vs) depth plot are attached to the conventional flat dilatometer testing equipment. From shear wave velocity profile, the stiffness at low strains of a site can be evaluated in undisturbed condition. And the resistivity value contains some information about water content and mineral characteristics of clayey soil. Specially manufactured resistivity and seismic modules were connected between commercialized DMT blade and drilling rod. To enhance reliability and repeatability of RSDMT test, automatic testing system including notebook based data acquisition system and automatic surface source system were developed. RSDMT system can be performed rapidly and can obtaine more reliable data at the same point compared with the separated testing system. The verification studies for the developed RSDMT system are going to be performed. From these studies, the effectiveness of integrated hybrid testing system will be checked in light of proper evaluation of geotechnical design parameters of clayey soils.