• Geomechanics and Engineering
• /
• 제30권6호
• /
• pp.579-586
• /
• 2022

Pile-supported structures are installed on saturated sloping grounds, where the ground stiffness may decrease due to liquefaction during earthquakes. Thus, it is important to consider saturated sloping ground and pile interactions. In this study, we conduct a centrifuge test of a pile-supported structure, and analyze the p-y_p loops, p-y_p loops provide the correlation between the lateral pile deflection (y_p) and lateral soil resistance (p). In the dry sand model (UV67), the p-y_p loops stiffness increased as ground depth increased, and the p-y_p loops stiffness was larger by approximately three times when the pile moved to the upslope direction, compared with when it moved to the downslope direction. In contrast, no significant difference was observed in the stiffness with the ground depth and pile moving direction in the saturated sand model (SV69). Furthermore, we identify the unstable zone based on the result of the lateral soil resistance (p). In the case of the SV69 model, the maximum depth of the unstable zone is five times larger than that of the dry sand model, and it was found that the saturated sand model was affected significantly by kinematic forces due to slope failure.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
• /
• pp.10-16
• /
• 1996

This study is aimed for investigating a decision of the saturated surface dry of crushed stone sand and measuring the moisture with increasing percentage of VFS(Very Fine Sand) replacement each crushed stone sand. The results indicated that moisture of crushed stone sand is generally increased with increasing percentage of VFS replacement and the rate of increase of moisture is about 30% every time that VFS replacement increases 3.5%. Also the saturated surface dry for crushed stone sane is proposed as a point of time where shape of flow-cone first slumps in this paper.

• Geomechanics and Engineering
• /
• 제2권1호
• /
• pp.29-44
• /
• 2010

Vertical vibration tests were conducted using model footings of different size and mass resting on the surface of finite sand layer with different height to width ratios which was underlain by either rigid concrete base, under both dry and saturated condition. The effect of saturation on the damping ratio of finite sand stratum underlain by a rigid base has been verified and compared with the results obtained for the case of finite dry sand stratum underlain by the rigid base. Comparison of results of the experimental study showed that the damping in both the cases is less than 10%. The damping ratio obtained for finite saturated sand stratum is marginally lower than that obtained on finite dry sand stratum at H/B ratio of 0.5. The difference between the two cases becomes significant when the H/B ratio increases to 3.0, indicating the significant influence of soil moisture on damping ratio of foundation- soil system with increase in the thickness of the finite sand stratum. Comparison of the predicted damping ratio for a homogeneous sand stratum with the experimental damping ratio obtained corresponding to the height to width ratio of 3.0 of the finite sand stratum underlain by the rigid concrete base indicates a significant reduction in damping ratio of the foundation-soil system for both the cases.

• 한국농공학회논문집
• /
• 제47권4호
• /
• pp.43-52
• /
• 2005

It is known in some literatures that the B value is not equal to unity in saturated soil when effective stress is given, in which the B Value is the ratio of measured excess pore water pressure and isometric loading pressure. In this study the B value was measured on various effective stresses and on various incremental loading stresses in various grain size of specimens with saturated sand. The test results showed that the B value was affected largely by grain size of sand in specimen and the amount of effective stress. There was the semi-logarithmic relationship between B value and effective stress, and also there was the linear relationship between the gradient of the former semi-logarithmic relationship and grain size of specimen.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권5호
• /
• pp.68-75
• /
• 1996

The vacuum drying characteristics of water-saturated porous media were studied experimentally. The water-saturated porous media, water-saturated sand layer, was heated by the isothermal bottom wall of the rectangular vessel. The vacuum drying rate and temperature distribution of the sand layer were measured and calculated under a variety of conditions of heated wall temperature, vacuum rate, and thickness of the test material. It was found that the drying rate due to the heat and mass teansfer is greatly influenced by the heated wall temperature, vacuum rate, and thickness of the test material.

• Geomechanics and Engineering
• /
• 제5권4호
• /
• pp.343-362
• /
• 2013

Simple relationships are proposed in this paper by modifying the Schmertmann's equation for settlement estimations of footings (i.e., $B/L{\approx}1$) carrying vertical loads in saturated and unsaturated sandy soils. The modified method is developed using model plate load tests (PLTs) and cone penetration tests (CPTs) results conducted in saturated and unsaturated sand in a controlled laboratory environment. Seven in-situ large-scale footings tested under both saturated and unsaturated conditions in sands were used to validate the proposed technique. The results of the study are encouraging as they provide reliable estimates of the settlement of shallow footings in both saturated and unsaturated sands using the conventional CPT results.

• 지구물리
• /
• 제6권2호
• /
• pp.107-119
• /
• 2003

The behavior of pore pressure and effective stress in a highly saturated sand bed under variations in the water pressure in its surface were investigated to determine the mechanism of the collapse of hydraulic structures during flooding or when attacked by storm waves. The vertical, one-dimensional model was used as a basic model to clarify the effect of water pressure variation on only to the vertical direction. The theoretical results show that a sand bed under variations of water pressure is weakened by an increase in excess pore pressure and that under certain conditions the sand bed will liquefy. Although many factors related to water pressure variation and property of the material determine this phenomenon, the mist important factor seems to be the small amount of air present in the sand bed. The theoretical results reported are verified by experiments.

• 한국지반공학회논문집
• /
• 제37권12호
• /
• pp.73-87
• /
• 2021

잔교식 구조물은 선박을 안전하게 접안하여 화물을 송수신할 수 있는 구조물로서, 포화된 경사지반에 주로 설치된다. 이러한 잔교식 구조물의 내진설계 시 기준서에서는 예비 설계 방법으로 응답스펙트럼해석법을 활용하도록 제시하고 있으나, 현재 포화지반에 관입된 잔교식 구조물의 모델링 방법에 대한 지침은 부족한 실정이다. 그러므로 본 연구에서는 포화지반에 관입된 잔교식 구조물의 내진성능을 평가하기 위해 동적원심모형실험 및 응답스펙트럼해석을 수행하였다. 동적원심모형실험을 위해 잔교식 안벽 말뚝 중 일부 구간(3×3 군말뚝)을 선정하였으며, 지반 포화 여부에 따라 2가지 모델(건조, 포화)로 분류하였다. 이후 실험 모델에 지반 스프링 방법을 적용하여 응답스펙트럼해석을 수행하였다. 실험 및 해석을 비교한 결과, 건조지반 모델 및 액상화가 발생하지 않는 포화지반 모델의 경우 모멘트 차이가 최대 51% 이내로 발생하였으며, 깊이 별 모멘트를 적절히 모사하는 것으로 나타났다. 그러므로 본 모델의 경우 Terzaghi(1955)가 제시한 수평지반반력상수를 활용하여 모델링을 수행하는 것이 적절한 것으로 판단된다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2000년도 봄 학술발표회 논문집
• /
• pp.387-394
• /
• 2000

In the present study, laboratory pull-out tests with screw anchors are carried out to investigate behavior characteristics of underground structures applied uplift seepage forces. Small scaled pull-out tests in sand were conducted under saturated condition. And then, it was observed that the upward displacement as well as the pullout load varied with spacing of the anchor. Also, analyses have been performed with the aim of pointing out the effects of various parameters on the group effect of the screw anchors.

• Earthquakes and Structures
• /
• 제11권1호
• /
• pp.83-107
• /
• 2016

In this study, the response and behavior of machine foundations resting on dry and saturated sand was investigated experimentally. A physical model was manufactured to simulate steady state harmonic load applied on a footing resting on sandy soil at different operating frequencies. Total of (84) physical models were performed. The parameters that were taken into consideration include loading frequency, size of footing and different soil conditions. The footing parameters are related to the size of the rectangular footing and depth of embedment. Two sizes of rectangular steel model footing were used. The footings were tested by changing all parameters at the surface and at 50 mm depth below model surface. Meanwhile, the investigated parameters of the soil condition include dry and saturated sand for two relative densities; 30 % and 80 %. The dynamic loading was applied at different operating frequencies. The response of the footing was elaborated by measuring the amplitude of displacement using the vibration meter. The response of the soil to dynamic loading includes measuring the stresses inside soil media by using piezoelectric sensors. It was concluded that the final settlement (St) of the foundation increases with increasing the amplitude of dynamic force, operating frequency and degree of saturation. Meanwhile, it decreases with increasing the relative density of sand, modulus of elasticity and embedding inside soils. The maximum displacement amplitude exhibits its maximum value at the resonance frequency, which is found to be about 33.34 to 41.67 Hz. In general, embedment of footing in sandy soils leads to a beneficial reduction in dynamic response (displacement and excess pore water pressure) for all soil types in different percentages accompanied by an increase in soil strength.