응력 Parameter에 관한 고찰

김방식 충주대 산업과학기술연구소 1994 産業科學論文集 Vol.2 No.-

The Streugth meant parameters of Soil have reserched in order to determine the failure Criterion and analyses for geotechnical Construction such as footings and retaining Walls. I studyed of some parameters in here as followers. 1. parameter of effective principle stress. P'=(σ1'+ σ2'+ σ3')/3=(σa'+2σr')/3 2. parameter of deviator stress in triaxial Condition ◁수식 삽입▷ (원문을 참조하세요) 3. parameter of plane Strain Condition. s'=(σ1'+σ3')/2, t=(σ1'+σ3')/2

자갈-모래 혼합토의 액상화 거동

김방식,강병희,윤여원 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.10

In this research, the effects of the gravel content on the liquefaction behavior for both of the isotropically and -anisotropically consolidated gravel-sand mixtures are investigated. For this purpose, the cyclic triaxial tests for the specimens with the same relative density (Dr=40%) and variations of gravel content were performed. On the other hand, a series of undrained cyclic triaxial tests were carried out on the isotropically consolidated gravel-sand mixtures with the same void ratio (e=0.7) and from 0% to 30% gravel contents. Void ratios of gravel-sand mixtures with the same relative density (Dr=40%) are found to decrease significantly with the increase of the gravel content from 0% to about 70% and increase thereafter. But the void ratio of the sand matrix among the gravel skeleton increases with the increase of the gravel contents. Test results are as follows : for the isotropically consolidated specimen with 40% of relative density and low gravel contents (GC=0%, 20%, 40%), pore water pressure development and axial strain behavior during undrained cyclic loading show similar behavior to those of the loose sand because of high void ratio, and the specimens with high gravel content (70%) both pore pressure and strain behaviors are similar to those of dense sand. And the isotropically consolidated specimens with the same void ratio (e=0.7) and higher gravel contents show the same behavior of pore water pressure and axial strain as that of the loose sand, but for the lower gravel content this behavior shows similar behavior to that of dense sand. The liquefaction strength of the isotropically consolidated specimens with the same relative density increases with gravel content up to 70%, and the strength decreases with the increase of the gravel content at the same void ratio. Thus, it is confirmed that the liquefaction strength of the gravel-sand mixtures depends both on relative density and void ratio of the whole mixture rather than the relative density of the sand matrix filled among gravels. On the other hand, the behavior of pore water pressure and axial strain for the -anisotropically consolidated gravel-sand mixtures shows almost the same cyclic behavior of the sand with no stress reversal even with some stress reversal of the cyclic loading. Namely, even the stress reversal of about 10% of cyclic stress amplitude, the permanent strain with small cyclic strain increases rapidly with the number of cycles, and the initial liquefaction does not occur always with less than maximum pore water pressure ratio of 1.0. The liquefaction resistance increases with the gravel contents between 0% and 40%, but tends to decrease beyond 40% of gravel content. In conclusion, the cyclic behavior of gravel-sand mixtures depends on factors such as gravel content, void ratio, relative density and consolidation condition.

모래의 액상화 거동에 미치는 인자

김방식 忠州大學校 2002 한국교통대학교 논문집 Vol.37 No.2

The factors affecting liquefaction susceptibility of saturated sands are in many occations and must be investigated to understand of it. From the comprehensive experimental results on reconstituted specimens, the behaviour of undrained and saturated sand is considerably affected by the fabric at the identical initial void ratio-effective stress state. Water pluviation specimen simulated in-situ behaviour very closely and very loose moist tamped specimen in different to in-situ sands. The sensitiveness to liquefaction is affected from static and cyclic depends on the initial state variation and effective stress path under undrained shear. The others are ability of the testing device, loading method and data aquisition system to measure the true behaviour of sands. Foundamental factors that influence liquefaction sensitiveness of saturated sands are considered in this study.

한국지반의 지하수 발달 특성

김방식 충주대 산업과학기술연구소 1999 産業科學論文集 Vol.7 No.2

We have been faced the crisis of local valuable water shortage seriously with increase of population, industrial development, improvement of lifetime, utilization of various life water and demand of water rapidly in these day. Furthermore, we are now received about environment problems becoming bad situation contaminated with complex industrial wastes and man-made pollution which would make water deficiency from drinking and have lost capability to prepare so safty fresh and clear water for our descendants. The clear water needs deep depth underground such as several hundred meter to it's water table for well it up with plenty of minerals and fresh taste, on this paper, studied of conception of ground-water, distribution of rock bed, movement of groundwater and relation between rock and groundwater in geological and hydrogeological features then researched quantity of natural groundwater in accordance with characteristic of geological distribution in south korea. Summing up, this study could make results of follows. 1.There are laid basaltic water aquifer and next comes are cavity aquifer, contact aquifer, rupture table and vein table from large to small amount of groundwater. 2.Rupture aquifer is smaller than weathered table in the quantity of grounfwater, and it makes confirmed the fields of weathered granite or gneiss well in possibility of groundwater development. 3.Welled groundwater have met at basaltic tectonics and limestone cavity type in the largest quantity according to geological structure and rocks.

반복하중하에서 조립질 흙의 액상화

김방식 충주대학교 2006 한국교통대학교 논문집 Vol.41 No.-

The effect of the gravel contents on the liquefaction behavior under the isotropical consolidated coarse grained soil as gravel-sand mixtured specimens are performed at the same relative density(Dr=40%) and void ratio(e=0.7) with various gravel contents in this research. The results of test of coarse grained soil showed that pore water pressure development and axial strain behavior during undrained cyclic loading represent the similar behavior to the loose sand mainly due to high void ratio for the isotropically consolidated specimen at the 40% of relative density with low gravel contents(0%, 20%, 40%), but, for the specimens with high gravel content(70%), both behaviors tend to be similar to the dense sand. At the same void ratio(e=0.7) with higher gravel contents show the same behaviors of pore water pressure development and axial strain as the loose sand behaviors due to lower relative density under the isotropically consolidated specimen, but, for the lower gravel content, these behaviors show the representative behavior of the dense sand. And the strength of liquefaction increases with decreasing the gravel content. Thus, it is confirmed that the liquefaction strength of the gravel-sand as coarse grained soils depends both on relative and void ratio of the whole mixture rather than the relative density of the sand matrix.

2004학년도 편입생 실태에 관한 조사연구

김방식,홍용희 충주대학교 학생생활연구소 2004 學生生活硏究 Vol.11 No.-

복합지반의 침하에 대한 영향인자의 평가

김방식,배우석 한국지반환경공학회 2007 한국지반환경공학회논문집 Vol.8 No.3

Stone columns is the ground improvement method which composed of compacted gravel or crushed stone inserted into the soft ground consisting of loose sand and clay. There are many difficulties in quantitative analysis of soil-pile interaction because settlement behavior of stone columns is affected by various parameters. In this study, various parameters of behavior of end-bearing group piles are investigated by load tests. Finally, the improved characteristics of soft ground and the influence of design parameters are investigated in this study using PR (performance ratio) value. From the PR value calculation and test results, we know that settlement behavior of stone columns is affected by area replacement ratio of composite ground, diameter of column rather than embedment ratio and mat. 쇄석말뚝은 느슨한 사질토지반이나 점토지반에 치환법에 의해 다져진 자갈이나 쇄석을 연약한 지반에 삽입하여 개량하는 공법이다. 쇄석말뚝 공법은 흙과 말뚝 접촉면에서 압밀거동이 다양한 인자에 의해 영향을 받게 되어 정량적인 해석에 많은 어려움이 있다. 본 연구에서는 재하시험을 통해 선단지지 군말뚝의 거동에 대한 다양한 인자의 영향을 조사하였다. 궁극적으로 연약지반의 개량 특성과 설계인자의 영향력을 PR값을 사용하여 평가하였다. 실험결과와 계산된 PR 값으로부터 쇄석말뚝의 침하거동이 근입비나 매트의 설치여부 보다는 말뚝의 직경이나 복합지반의 치환율에 의해 영향을 받고 있음을 알 수 있다.

반복하중하에서 자갈질 흙의 특성평가

김방식 忠州大學校 2004 한국교통대학교 논문집 Vol.39 No.2

자갈 혼입량을 중량비로 0%, 20%, 40%, 60% 및 70%로 혼합시킨 자갈-모래 혼합시료에 대한 비배수 반복삼축시험을 행하여 반복액상화 저항과 자갈혼입량과의 관계에 대해서 분석하였다. 시험결과 자갈의 혼입량 증가에 따라 액상화 반복저항은 증가됨을 알 수 있었다. 혼합시료의 자갈혼입량 증가에 따른 최대ㆍ최소 건조밀도는 자갈혼입량 70%에서 정점을 나타내며 그 이후에는 점감하게 되며 최대ㆍ최소 간극비는 이의 반대경향을 보여준다. Undrained cyclic triaxial tests were performed on gravel-sand composite specimens with gravel contents of 0%, 20%, 40, 60% and 70% to evaluate the effect of gravel content on the liquefaction resistance of that specimens. The result of test showed that the liquefaction resistance of gravel-sand specimens increased with increasing gravel content. The relation between the maximum and minimum dry composite densities versus gravel content for the materials tested in this study. The maximum and minimum dry densities increased with increasing gravel content from 0% to 70%. It appeared that the density decreased with increasing gravel content beyond 70%. The relationship between maximum and minimum composite void ratio versus gravel content showed that the void ratio of gravel-sand composite decreased with gravel content increases from 0% to 70% and then the void ratio increased with gravel contents over 70%.

2004학년도 신입생 실태에 관한 조사연구

김방식,홍용희 충주대학교 학생생활연구소 2004 學生生活硏究 Vol.11 No.-

지반 불확실성을 고려한 연직배수재 배치간격의 확률론적 해석과 결정

김방식,김병일 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.4

본 연구에서는 표준압밀, 방사형 일정변형속도 압밀, 로우셀압밀, 복합통수능 및 교란영역시험을 수행하여 연직배수공법의 신뢰성 설계를 위한 파라미터를 산정하였다. 또한 방사형 압밀이론에 대한 민감도 해석, 결정론적 해석 및 확률론적 해석이 수행되었다. 시험 결과를 이용한 방사형 압밀이론의 확률론적 해석 결과와 결정론적 해석 결과를 비교, 분석 하였으며, 그로부터 배수재 배치간격은 확률론적 방법보다 결정론적 방법에서 더 넓게 산정됨을 제시하였다. 이는 결정론적 해석에서는 지반 불확실성을 고려하지 못하였기 때문이다. 두 방법을 이용하여 산정된 배치간격간의 차이는 목표 압밀도에 도달할 수 있는 확률과 수평압밀계수의 변동계수에 영향을 받는 것으로 나타났다.