연약점토지반에 성토 등의 상재하중을 재하하게 되면 측방유동이라고 하는 측방변위가 발생하게 된다. 이 측방유동은 파일기초의 변형, 교대의 이동, 지중매설관의 파괴 등 성토에 인접한 지중구조물에 피해를 가하게 된다. 그렇지만, 측방유동은 체적변형과 전단변형도 동시에 발생할 뿐만 아니라 이 측방유동에 영향을 미치는 인자가 많기 때문에 측방유동에 의해서 발생하는 측방토압의 발생 메커니즘이 아직 명확히 밝혀지지 않았다. 그리고 최근 근접시공 등 기존구조물에 근접해서 공사가 진행되는 경우가 많아 이러한 근접구조물에 어떠한 피해를 가할 것인가 또는 대책공법을 설계하기 위한 설계하중으로서 측방토압을 구해야 하는 필요성이 커지고 있는 것 또한 현실이다. 그러므로 본 연구에서는 성토에 의해서 연약지반에 발생하는 측방토압에 미치는 재하속도의 영향을 조사하기 위해서 실내모형실험을 실시하였다. 그 결과, 측방토압이 삼각형 분포를 이룬다는 것과 재하속도가 빠를수록 측방토압의 최대치가 커지고 부등침하가 커진다는 것을 알 수 있었다. 그리고 이러한 재하속도의 영향은 부의 dilatancy에 의한 과잉간극수압의 발생에 기인한다는 것을 알았다.
연약점토지반에 성토 등의 상재하중을 재하하게 되면 측방유동이라고 하는 측방변위가 발생하게 된다. 이 측방유동은 파일기초의 변형, 교대의 이동, 지중매설관의 파괴 등 성토에 인접한 지중구조물에 피해를 가하게 된다. 그렇지만, 측방유동은 체적변형과 전단변형도 동시에 발생할 뿐만 아니라 이 측방유동에 영향을 미치는 인자가 많기 때문에 측방유동에 의해서 발생하는 측방토압의 발생 메커니즘이 아직 명확히 밝혀지지 않았다. 그리고 최근 근접시공 등 기존구조물에 근접해서 공사가 진행되는 경우가 많아 이러한 근접구조물에 어떠한 피해를 가할 것인가 또는 대책공법을 설계하기 위한 설계하중으로서 측방토압을 구해야 하는 필요성이 커지고 있는 것 또한 현실이다. 그러므로 본 연구에서는 성토에 의해서 연약지반에 발생하는 측방토압에 미치는 재하속도의 영향을 조사하기 위해서 실내모형실험을 실시하였다. 그 결과, 측방토압이 삼각형 분포를 이룬다는 것과 재하속도가 빠를수록 측방토압의 최대치가 커지고 부등침하가 커진다는 것을 알 수 있었다. 그리고 이러한 재하속도의 영향은 부의 dilatancy에 의한 과잉간극수압의 발생에 기인한다는 것을 알았다.
When an embankment is constructed on soft clay ground, the lateral displacement generally called as lateral flow is generated in the foundation ground. It strongly affects stabilities of structures, such as foundation piles and underground pipes, in and on the foundation ground. The lateral earth pr...
When an embankment is constructed on soft clay ground, the lateral displacement generally called as lateral flow is generated in the foundation ground. It strongly affects stabilities of structures, such as foundation piles and underground pipes, in and on the foundation ground. The lateral earth pressure induced by the lateral flow is influenced by the magnitude and construction speed of embankment, the geometric conditions and geotechnical characteristics of the embankment, and the foundation ground, and so on. Accurate methods for estimating the lateral earth pressure have not ever been established because the lateral flow of a foundation ground shows very complicated behavior, which is caused by the interaction of shear deformation and volumetric deformation. In this paper, a series of model tests were carried out in order to clarify effects of construction speed of an embankment on the lateral earth pressure in a foundation ground were design. It was found that the magnitude and the distribution of the lateral earth pressure and its change with time are dependent on the construction speed of the embankment. It was found that a mechanism for the lateral earth pressure was generated by excess pore water pressure due to negative dilatancy induced by shear deformation under the different conditions of construction speeds of embankments.
When an embankment is constructed on soft clay ground, the lateral displacement generally called as lateral flow is generated in the foundation ground. It strongly affects stabilities of structures, such as foundation piles and underground pipes, in and on the foundation ground. The lateral earth pressure induced by the lateral flow is influenced by the magnitude and construction speed of embankment, the geometric conditions and geotechnical characteristics of the embankment, and the foundation ground, and so on. Accurate methods for estimating the lateral earth pressure have not ever been established because the lateral flow of a foundation ground shows very complicated behavior, which is caused by the interaction of shear deformation and volumetric deformation. In this paper, a series of model tests were carried out in order to clarify effects of construction speed of an embankment on the lateral earth pressure in a foundation ground were design. It was found that the magnitude and the distribution of the lateral earth pressure and its change with time are dependent on the construction speed of the embankment. It was found that a mechanism for the lateral earth pressure was generated by excess pore water pressure due to negative dilatancy induced by shear deformation under the different conditions of construction speeds of embankments.
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문제 정의
Therefore, a method for estimating the lateral earth pressure must consider these factors. Therefore, this paper focused on the effects of the construction speeds of embankment to the lateral earth pressure caused in the foundation ground.
가설 설정
(3) The vertical distribution of the lateral earth pressure can be regarded as a triangular distribution. The maximum value of the lateral earth pressure was about 0.
제안 방법
Because the magnitude and distribution of the lateral earth pressure depend on the strength of foundation ground, a homogeneous ground with a uniformly distributed strength was selected for lG-model tests in this study and thereby loading to find the influence of the construction speed of embankment as the factor affecting the lateral earth pressure. In addition, centrifuge model tests are planned following a series of the IG-model tests in this study.
Because the magnitude and distribution of the lateral earth pressure depend on the strength of foundation ground, a homogeneous ground with a uniformly distributed strength was selected for lG-model tests in this study and thereby loading to find the influence of the construction speed of embankment as the factor affecting the lateral earth pressure. In addition, centrifuge model tests are planned following a series of the IG-model tests in this study. The magnitude and distribution of the lateral earth pressure are to be investigated in the centrifuge model tests on the foundation ground, where the strength increases with depth, in order to clarify the difference of the strength distribution in the foundation ground behavior.
In this study, the lateral earth pressure acting on a rigid retaining structure installed at the toe of an embankment, which is considered to be the largest value, was investigated using a model container as shown in Fig. 1. The model container used was 600 mm in length and 200 mm in width.
In practice, the largest value in the predicted lateral earth pressure is often used as a design value in the viewpoint of safety. In this study, the lateral earth pressure acting on the rigid retaining structures installed at the toe of an embankment, which is considered to be the largest value, was investigated using a model container as shown in Fig. 1.
It was found from the test results that the magnitude and the distribution of the lateral earth pressure and their change with time are varied with the construction speed of an embankment. Observations of tests were compared with the results of numerical solutions for estimating stresses caused by an embankment load based on the elasticity theory.
Because the gradient of embankment slope in the case of neighboring constructions causing problems of the later시 flow is generally made large by reinforced earth methods or others, a large gradient of embankment slope was used in this study. The height of the model container was determined to have enough depth so as to obtain a peak value of the lateral earth pressure in the vertical distributions based on the elasticity theory and the FEM analyses derived in this study. To negate the effects of sidewall friction, the width of the model container was desired to have enough width and sidewalls of model container were lubricated with silica grease.
The model tests were carried out herein to estimate the lateral earth pressures either on the sheet piles or continuous rigid walls that are installed to reduce the lateral flow at the toe of the embankment. It is well known that the magnitude of the lateral earth pressure is dependent on the rigidity of a retaining structure for the lateral flow.
대상 데이터
The steel plates were fixed around the model container to prevent the deformation of acrylic plates due to the action of the earth pressures. Eight pore water transducers of the attached type (PS-1KC, Max =98 kPa, Kyowa Co.), four pore water transducers of the penetrated type (PDCR81, Max =98 kPa, Druck Limited Co.) and eleven earth pressure transducers (PGM-1 KG, Max =98 kPa, Kyowa Co.) were installed in order to measure the excess pore water pressure and the lateral earth pressure at various locations as shown in Fig. 1.
The clay used was alluvial marine clay called Dejima clay, which obtained from Hiroshima Bay, Japan. The collected clay was remolded and sieved through 0.
1. The model container used was 600 mm in length and 200 mm in width. Its height was 850 mm during the preconsolidation and 500 mm during the embankment loading.
In this study, however, 200 mm of the width was determined consi- dering the maximum value due to the limitation of the preparation of the volxime of the clay slurry in the laboratory. The model container was made by acrylic plates. The steel plates were fixed around the model container to prevent the deformation of acrylic plates due to the action of the earth pressures.
성능/효과
(1) When the construction speed of embankment increased, the amount of the surface settlements at the center and the toe of embankment decreased though at slightly inside of the embankment shoulder increased. The position of the peak value of the surface settlement was changed from the center of embankment to slightly inside of the embankment shoulder and the shear deformation under the slope of the embankment in clay ground increased with the increase of the construction speed of the embankment.
(2) The excess pore water pressure at the upper clay layer under the toe of embankment was larger and its dissipation was slower than that at the lower clay layer. This is considered to be due to the shear deformation, which occurred largely in the upper clay layer than in the lower clay layer in the loading stage and the early consolidation stage.
It was found from the test results that the magnitude and the distribution of the lateral earth pressure and their change with time are varied with the construction speed of an embankment. Observations of tests were compared with the results of numerical solutions for estimating stresses caused by an embankment load based on the elasticity theory.
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