상재하중의 재하위치 및 매설심도를 고려한 지중 매설관의 구조거동 평가

류연선(Ryu Yeon Sun),조현만(Cho Hyun Man),김영빈(Kim Young bin) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.2

지중매설관은 산업의 각종분야 및 지하 기반시설에 널리 사용되고 있다. 지중 매설관에 작용하는 하중으로는 토압, 차량하중, 온도, 지진 하중, 부양하중 등이 있다. 특히 다수의 매설관은 도로 포장아래에 매설되어 있고, 과도한 차량하중이나 예상치 못한 하중을 받는 경우가 있다. 본 논문에서는 매설관의 상부 및 인근에 상재하중이 작용할 때 나타나는 매설관의 구조적 거동을 상재하중의 재하위치, 매설관의 매설깊이, 매설관의 크기를 고려하여 평가하였다. 이를 위해 수치모델을 구성하고 유한요소해석을 수행하였다. 매설깊이와 재하위치에 따라 매설관의 변위와 응력의 변화를 산정하고, 그 결과로부터 거동특성을 파악하였다. Buried pipes have been applied in a wide range of industry and the subsurface infrastructures. The loads acting on buried pipes include soil pressure, traffic load, seismic load, flotation. Many underground pipes are buried under the road pavement and subjected to excessive vehicle load or unexpected load. In this paper, the structural behavior of the buried pipe under the surcharge load is evaluated considering load location, buried depth and dimension of pipe. Finite element analysis was perform for the assessment of the displacement and stress of buried pipe. The results showed the effect of the load location and buried depth on performance of the underground pipe.

좁은 공간 되메움 지반에서의 상재하 영향에 의한 토압

문창열,이종규 한국지반공학회 1997 지반 : 한국지반공학회지 Vol.13 No.6

건물의 지하외벽 또는 암거나 박스 칼버트와 같은 지하구조물은 되메움한 흙의 자중에 의한 하중 이외에 되메움이 완료된 후 주차장을 신설하거나 도로를 건설하면 차량이나 구조물에 의해 표면에 작용하는 점하중, 띠하중, 선하중 등의 외부 하중을 지자하게 된다. 이러한 상재하중에 의한 지중응력은 구조물에 영향을 받아 수평압력 및 연직압력을 증가시킨다. 상재하중에 의해 증가하는 지중응력을 계산하는 방법은 지반이 반무한 탄성체이며 등방성이고 균질하다는 가정하의 Boussinesq(1885)의 탄성론에 의한 지중응력 산정법과 지반은 등향적(imtropic)이고 균질하며 활동선이 Coulomb의 기준에 맞는다라는 가정하에 Krey(1936), Ohde(1952) 등의 소성론에 따른 산정법 및 이를 조합한 Schmitt(1992) 등이 제시한 탄소성론에 의한 산정 법등이 제시되었다. 본 연구에서는 탄소봉으로 지반을 조성한 후 되메움 공간의 크기가 다른 경우 그 표면에 등분포 띠 하중으로서 상재하중이 작용할 때 증가되는 수평토압의 크기, 벽체에 작용하는 토압에 의한 수직압력 및 굴착면 하부에 작용하는 연직토압을 측정하여 상재하중과토압의 관계를규명하였다. 또한, Mohr-Coulomb의 지반구성모델을 이용한 유한차분법 (FDM)으로 해석하여 그 결과를 실험 결과와 비교, 검토하였다. The structure such as underground external walls of buildings, conduit and box culvert supports the surcharge loads (point, strip and line loads) . The vertical and horizontal stresses in a soil mass depend on the backfill width and wall friction, etc. The investigations described in this paper is designed to identify the magnitude and the distributions of the lateral and vertical pressure which is occurred by the narrowly backfilled soil in an open cut by the surcharge loads. For these purposes, model tests were performed for various width of backfill in a model test box by considering the wall friction using carbon rods. The results of test were compared with the theories of Weissenbach and VS Army Code and also with the results of the numerical analysis using finite difference method which introduces Mohr-Coulomb failure hypothesis.

실대형 교각 실험을 통한 교각 세굴안정성 평가 실험 기법 정립

이명재,유민택,김기현,이일화 한국지반공학회 2019 한국지반공학회논문집 Vol.35 No.7

In this study, a prototype abutment was constructed to establish a safety assessment technique of pier and a series of non-destructive tests using impact load. The surcharge load was loaded from 0 tonf to 2.5 tonf on the prototype abutment, and maximum surcharge load was up to 25 tonf. To analyze the behavior of the piers according to the direction of impact, a total of three types of analysis were performed: the direction of the pier, the direction perpendicular to the pier, and the outer direction of the pier. The height of the impact was also tested at each top and bottom. The measuring instrument used an accelerometer to measure the acceleration response when impacted. Based on the series of experimental results, specific values were calculated according to the direction of an impact and the surcharge load using the Fast Fourier Transform (FFT). In addition, the phase difference was used to analyze the pier from the primary 1st mode to the 4th mode.

상재하중의 크기와 이격거리에 따른 강성벽체의 토압분포

오범진,이상덕 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.12

Earth pressure due to gravity generally increases linearly with the depth, but the distribution of earth pressure due to surface load depends on the loading condition, the ground condition, and the boundary condition. In this study, the earth pressure on a rigid wall due to the vertical surface load was measured in experiments. Rigid wall was built in the model test box, and it was filled with homogeneous sandy ground (width 30 cm, height 88 cm, length 110 cm). Rigid wall was composed of 8 segments, which were tested on the two load cells. In the tests, we observed the distribution of the earth pressure on the rigid wall depending on the vertical surface load and it’s location. According to the test results, the lateral earth pressure due to the vertical surface load showed its maximum value at a constant depth and decreased with the depth, to the negligible value at the critical depth. The critical depth and the depth at which lateral earth pressure reaches its maximum were not decided by the magnitude of the vertical surface load. They were dependant on the distance from the rigid wall.

과재하중 재하에 따른 역 T형 옹벽의 활동거동에 관한 수치해석

유남재,이명욱,박병수,이승주 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.B

This paper is experimental and numerical research about the sliding behavior of cantilever retaining walls resisting surcharge loads. In experimental research, centrifuge model tests at the 1g and 40g-level were performed by changing the location of model footing and its width. Bearing capacity of model footing and characteristics of load-settlement and load-lateral displacement of retaining wall were investigated. Test results of bearing capacity were compared with modified jarquio method, based on the limit equilibrium method with elasticity theory. For the numerical analysis, the commericially available program of FLAC was used by implementing the hyperbolic constitutive relationships to compare with test result about load-settlement and load-displacement of retaining wall, bearing capacity of strip footing.

An analytical expression for the dynamic active thrust from c-φ soil backfill on retaining walls with wall friction and adhesion

Shukla, Sanjay K.,Bathurst, Richard J. Techno-Press 2012 Geomechanics & engineering Vol.4 No.3

This paper presents the derivation of an analytical expression for the dynamic active thrust from c-${\phi}$ (c = cohesion, ${\phi}$ = angle of shearing resistance) soil backfill on rigid retaining walls with wall friction and adhesion. The derivation uses the pseudo-static approach considering tension cracks in the backfill, a uniform surcharge on the backfill, and horizontal and vertical seismic loadings. The development of an explicit analytical expression for the critical inclination of the failure plane within the soil backfill is described. It is shown that the analytical expression gives the same results for simpler special cases previously reported in the literature.

Deformation Response Induced by Surcharge Loading above Shallow Shield Tunnels in Soft Soil

Zhen Huang,Hai Zhang,Helin Fu,Shaokun Ma,Ying Liu 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.8

In the case of sudden surcharge loading, shallow shield tunnels in areas with soft soil experience substantial deformation responses. It is very important to understand the different loading modes and control measures above the shallow shield tunnels in soft soil for improving the safety of tunnel structure and reducing the influence of deformation. In this study, a three-dimensional numerical model of shallow shield tunnels in soft soil is established with FLAC3D. Ground and tunnel deformations are analyzed under different loading modes, and the effects of different deformation control measures are also studied. The numerical simulations in this paper show that the surface and tunnel deformation responses vary when induced by different loading modes above shallow shield tunnels in soft soil. After surface hardening with a 20-cm-thick layer of C20 concrete, the surface settlement is effectively controlled, and the uneven longitudinal settlement of the tunnel vault is improved. However, controlling the height of the surcharge is the most direct deformation control method. When the height of the surcharge is reduced from 6 m to 4 m and 2 m, the maximum ground settlement is reduced by 37.8% and 69.4%, respectively, and the maximum longitudinal settlement of the tunnel vault is reduced by 35.3% and 65.2%, respectively. During the operation of shallow shield tunnel in soft soil area, sudden surcharge loading should not be allowed. In the inevitable case, the surcharge loading on one side of the tunnel should be prevented and the surcharge loading height should be strictly limited.

상재하중을 받는 토류벽체의 거동에 관한 모형실험 연구

정온수,허경한,Jung. On-Su,Huh. Kyung-Han 한국방재학회 2005 한국방재학회논문집 Vol.5 No.4

본 연구에서는 상재하중을 적용한 굴착모형실험을 통하여 상재하중 적용으로 인한 굴착단계별, 벽체강성 및 지반조건에 따른 토류벽체의 수평변위, 배면지반 지표침하, 토류벽체에 적용되는 토압변화 및 분포에 대하여 실험결과치, 이론치 및 현장자료 분석치와 상호비교, 분석하여 상재하중 적용에 의한 영향을 규명하였다. 그 결과 상재하중이 적용된 모형지반에서의 지표침하곡선 형태는 상재하중 미 적용시 지표침하 곡선형태의 정규확률 분포곡선과 달리 상재하중 중앙 부분이 최대 침하를 일으키는 포물선 형태의 침하를 보이고 있으며, 굴착단계별 상재하중 적용으로 인한 벽체최대수평변위는 최종굴착시에 0.8H(보:굴착깊이) 지점에서 벽체의 최대수평변위가 발생하였으며, 상재하중 적용에 따른 벽체변위량의 증가범위는 벽체상부로부터 하중이격거리에 2배의 깊이까지 증가범위를 보였다. 또한, 굴착단계별 지표면의 침하로 인한 기초판의 각 변위는 최종단계에서의 각 변위가 가장 크게 발생하였고, 벽체강성별로는 두께 4mm(유연계수 <TEX>${\rho}\;:480m^3/t$</TEX>) 벽체가 두께 9mm(유연계수 <TEX>${\rho}\;: 40m^3/t$</TEX>)보다 최대 3배 이상 발생하고 있어 벽체강성의 영향이 매우 큼을 알 수 있다. The purpose of this study is to closely examine the influence of the surcharge load applied to the retaining wall through some model tests, in which wall stiffness in each stage of excavation, horizontal displacement of the retaining wall and surface displacement of the backfill according to wall stiffness and ground conditions, and change and distribution of the earth pressure applied to it were measured and their values were produced, then these values were mutually compared with their theoretical values and their values after analysis of the data obtained at the field, and they were analytically studied, in order to closely examine the influence of the surcharge load applied to the retaining wall. Findings from this study are as follows: The shape of ground surface settlement curve on the model ground under surcharge load, different from the distribution curve of regular probabilities which is of a shape of ground surface settlement under no surcharge load, appears in that settlement in an arching shape shows where the center part of surcharge load shows the maximum settlement. In examining the maximum horizontal displacement with the surcharge load applied to each stage of excavation, it occured at the point of 0.8H(excavation depth) when finally excavated. Regarding the range in which the displacement of the retaining wall increases according to application of surcharge load, the increment of displacement showed till the point of depth which is of two times of the distance of load from the upper part of the wall. Also since each displacement of the foundation plate caused by the ground surface settlement according to each stage of excavation occured most significantly at the final stage. Also since regarding wall stiffness, the wall of its thickness of 4mm(flexible coefficient <TEX>$p:480m^3/t$</TEX>), produced maximum 3 times of wall stiffness than its thickness of 9mm(flexible coefficient <TEX>$p: 40m^3/t$</TEX>), it was found out that influence of wall stiffness is so significant.

프리캐스트 옹벽 마이크로 파일의 보강 효율

문창열(Moon Changyeul) 한국지반환경공학회 2008 한국지반환경공학회논문집 Vol.9 No.7

본 연구에서는 좁게 형성되는 프리캐스트 옹벽 배면에 상재하중을 재하 하였을 경우 마이크로파일의 수평저항 거동에 대한 설치 효율성을 규명하고자 하였다. 이를 확인하기 위한 수단으로 모형시험과 수치해석을 수행 하였다. 실내모형시험은 모형토조에 기초지반 조성 후 모형옹벽을 설치하였으며, 옹벽 배면에 상재하중을 재하 하여 마이크로파일의 설치간격 및 길이 등을 각각 변화시켜 수행하였다. 본 연구에서 보강된 마이크로파일이 프리캐스트 옹벽에 발생하는 수평방향 변형을 효과적으로 억제하는 것으로 나타났다. 마이크로파일의 간격을 좁게 설치하고 파일의 길이가 길어질수록 보강효율이 증가하는 경향을 보이며, 파일의 길이가 0.5H 설치간격은 7D에서 최적의 보강효율을 나타내는 것으로 평가되었다. This study investigates the lateral resistance of micro-pile system when surcharge load is acting on the back of retaining wall. Both laboratory experiments and numerical analysis were performed. The experimental retaining wall model was developed on the laboratory-sized foundation. While surcharge load was acting, the interval and length varied as experimental variables. From the investigation it is known that the micro-pile system can effectively control the lateral displacement which is developed on the precast retaining wall. The effectiveness became increased as the pile interval reduced and the length of pile increased. The greatest reinforcing efficiency was shown when the pile length was 0.5H and the interval was 7D.

보강재 설치 간격에 따른 지오그리드 보강토옹벽의 변형거동에 관한 모형실험

조삼덕,안태봉,이광우,오세용 한국지반공학회 2004 한국지반공학회논문집 Vol.20 No.5

The model tests are conducted to assess the behavior characteristics of geogrid reinforced soil walls according to different surcharge pressures and reinforcement spacings. The models are built in the box having dimension, 100cm tall, 140cm long, and 100cm wide. The reinforcement used is geogrid(tensile strength 2.26t/m). Decomposed ganite soil(SM) is used as a backfill material. The strain gauges and LVDTs are Installed to obtain the strain in the reinforcements and the displacements of the wall face. From the results, it can be concluded that the more the reinforcement tensile strength increases, the more the wall displacements and the geogrid strains decreases. The maximum wall displacements and geogrid strains of the model walls occur due to the uniform surcharge pressure at the 0.7H from the bottom of the wall. The horizontal displacements of the wall face nonlinearly increase with the increase of surcharge pressures, and this nonlinear behavior is significantly presented for larger surcharge due to the nonlinear tensile strength-strain relationship of the reinforcements. 상재하중 및 보강재의 포설 간격이 보강토옹벽의 변형거동에 미치는 영향을 평가하기 위하여 일련의 모형실험을 수행하였다. 모형 보강토옹벽은 $100cm \times 140 \times 100cm$ 크기의 모형토조내에 축조하였다. 본 모형실험에서는 보강재로 인장강도 2.26t/m의 지오그리드를 사용하였고, 뒤채움흙으로는 통일분류법상 SM에 해당되는 화강풍화토를 사용하였다. 모형옹벽 축조후 상재하중 재하에 따른 벽체수평변위와 보강재의 인장변형을 측정하였다. 실험결과, 상재하중이 증가할수록 모형 보강토옹벽의 벽체변위 및 보강재 인장력이 증가하였다. 벽체 최대수평변위 및 보강재 최대 인장력은 벽체 하단으로부터 0.7H 지점에서 측정되었으며, 그 크기는 상재하중이 증가할수록 변형증가율이 커지는 비선형적인 형태를 보였다.