The Surface Settlement Law of Precipitation in Pile-Beam-Arch Station Adjacent to Pile Foundation

Yunsi Liu,Yueyuan Huang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.4

The pile foundations of adjacent buildings can have an impact on the precipitation process in subway stations. In this paper, surface settlement monitoring is carried out by precipitation of horizontal wells in subway stations, and the law of surface settlement change with and without neighboring pile foundations is studied. The influence law of surface settlement in subway stations under different pile depth, different pile spacing and different distance between piles and station boundary is obtained through numerical simulation. Three models of groundwater infiltration in the adjacent pile foundation were established, the principle of pile-soil permeability coefficient equivalence was proposed, and the function relationship between the equivalent soil permeability discount factor and pile parameters was derived. The research results show that the surface settlement is smaller when there are piles in the measured precipitation process than when there are no piles. The greater the pile depth, the smaller the pile spacing and the smaller the pile-station boundary, the stronger the barrier effect and the smaller the final settlement of the ground surface. The accuracy of the formula is also analyzed to show that changing the pile parameters also changes the permeability coefficient of the piles and the soil between the piles. The station surface settlement law is related to the pile parameters, and the study can provide an important theoretical reference for the construction of precipitation with adjacent pile foundations.

A new analytical model to determine dynamic displacement of foundations adjacent to slope

Varzaghani, Mehdi Imani,Ghanbari, Ali Techno-Press 2014 Geomechanics & engineering Vol.6 No.6

Estimating seismic displacements has a great importance for foundations on or adjacent to slope surfaces. However, dynamic solution of the problem has received little attention by previous researchers. This paper presents a new analytical model to determine seismic displacements of the shallow foundations adjacent to slopes. For this purpose, a dynamic equilibrium equation is written for the foundation with failure wedge. Stiffness and damping at the sliding surface are considered variable and a simple method is proposed for its estimation. Finally, for different failure surfaces, the calculated dynamic displacement and the surfaces with maximum strain are selected as the critical failure surface. Analysis results are presented as curves for different slope angles and different foundation distances from edge of the slope and are then compared with the experimental studies and software results. The comparison shows that the proposed model is capable of estimating seismic displacement of the shallow foundations adjacent to slopes. Also, the results demonstrate that, with increased slope angle and decreased foundation distances from the slope edge, seismic displacement increases in a non-linear trend. With increasing the slope angle and failure wedge angle, maximum strain of failure wedge increases. In addition, effect of slope on foundation settlement could be neglected for the foundation distances over 3B to 5B.

Dynamic modeling of embedded curved nanobeams incorporating surface effects

Ebrahimi, Farzad,Daman, Mohsen Techno-Press 2016 Coupled systems mechanics Vol.5 No.3

To investigate the surface effects on vibration of embedded circular curved nanosize beams, nonlocal elasticity model is used in combination with surface properties including surface elasticity, surface tension and surface density for modeling the nano scale effect. The governing equations are determined via the energy method. Analytically Navier method is utilized to solve the governing equations for simply supported at both ends. Solving these equations enables us to estimate the natural frequency for circular curved nanobeam including Winkler and Pasternak elastic foundations. The results determined are verified by comparing the results by available ones in literature. The effects of various parameters such as nonlocal parameter, surface properties, Winkler and Pasternak elastic foundations and opening angle of circular curved nanobeam on the natural frequency are successfully studied. The results reveal that the natural frequency of circular curved nanobeam is significantly influenced by these effects.

A simple shear deformation theory based on neutral surface position for functionally graded plates resting on Pasternak elastic foundations

Abdeljalil Meksi,Samir Benyoucef,Mohammed Sid Ahmed Houari,Abdelouahed Tounsi 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6

In this work, a novel simple first-order shear deformation plate theory based on neutral surface position is developed for bending and free vibration analysis of functionally graded plates and supported by either Winkler or Pasternak elastic foundations. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations of the present theory is reduced, and hence, makes it simple to use. The governing equations are derived by employing the Hamilton’s principle and the physical neutral surface concept. There is no stretching–bending coupling effect in the neutral surface-based formulation, and consequently, the governing equations and boundary conditions of functionally graded plates based on neutral surface have the simple forms as those of isotropic plates. Numerical results of present theory are compared with results of the traditional first-order and the other higher-order theories reported in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static bending and free vibration behaviors of functionally graded plates.

A simple shear deformation theory based on neutral surface position for functionally graded plates resting on Pasternak elastic foundations

Meksi, Abdeljalil,Benyoucef, Samir,Houari, Mohammed Sid Ahmed,Tounsi, Abdelouahed Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6

In this work, a novel simple first-order shear deformation plate theory based on neutral surface position is developed for bending and free vibration analysis of functionally graded plates and supported by either Winkler or Pasternak elastic foundations. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations of the present theory is reduced, and hence, makes it simple to use. The governing equations are derived by employing the Hamilton's principle and the physical neutral surface concept. There is no stretching-bending coupling effect in the neutral surface-based formulation, and consequently, the governing equations and boundary conditions of functionally graded plates based on neutral surface have the simple forms as those of isotropic plates. Numerical results of present theory are compared with results of the traditional first-order and the other higher-order theories reported in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static bending and free vibration behaviors of functionally graded plates.

지반 및 원형기초의 특성이 기초의 동적거동에 미치는 영향

안재훈,Ahn. Jae-Hun 한국방재학회 2008 한국방재학회논문집 Vol.8 No.2

지반 및 원형기초의 물성이 그 기초의 수직 동적거동에 미치는 영향이 해석적 해와 수치해석을 통해 연구되었다. 해석적 해로는 반무한체 지반 위 원형기초의 거동을 나타내는 간략 해가, 수치해석방법으로는 선대칭 유한요소법이 consistent transmitting 경계조건과 함께 사용되었다. 균일한 지반의 물성으로서의 전단파속도는 원형기초 동적거동의 공명진동수에 영향을 주었으나 공명진동시의 최대반응값에는 영향을 미치지 않았다. 같은 경우에 지반의 밀도는 공명진동수와 최대반응값에 모두 영향을 주었다. 균일한 지반 위 원형기초의 크기와 질량도 원형기초 동적거동의 공명진동수와 최대반응값 모두에 영향을 주었으나 균일 지반의 포아송비는 큰 영향을 미치지 않는 것으로 나타났다. 지반이 균일하지 않고 층이 존재할 경우에 각 층의 물성으로의 전단파속도들의 상관관계는 원형기초의 최대반응값에 영향을 주었다. The effect of characteristics of ground and circular foundation on the dynamic behavior of the foundation in vertical motion are considered using an approximated analytical solution and a finite element analysis with absorbing (consistent transmitting) boundary. The shear wave velocity of homogeneous ground affects the resonant frequency of the foundation much but has nothing to do with the maximum response amplitude at resonant frequency. The density in this case affects both the resonant frequency and the maximum response. The size and the mass of the circular foundation are related both to the resonant frequency and the maximum response. However, Poisson`s ratio has very little effect on dynamic behavior of the foundation. When the ground is not homogeneous but has the layers, different formations of shear wave velocities would also change the maximum response at resonant frequency.

신라시대 교량 월정교 교각기초의 복원안정성 연구

이광우,홍기권,유승경 한국지반신소재학회 2019 한국지반신소재학회 논문집 Vol.18 No.4

A derelict bridge called WoljungGyo was restored in Gyeongju, the capital city of ancient Silla. WoljungGyo was originally built in 760AD, and later rebuilt in 1280AD during the Goryeo Kingdom. The bridge lasted in working condition for at least 520 years. The bridge was uncovered to the remains of both abutments and four piers, with only one or two steps remaining. One of the foundation for piers showed evidence of partial settlement. The cause of the partial settlement is important for the successful restoration of the bridge so that an extensive investigation was carried out, which includes layer stratification by boring, 2-D stiffness profiling by surface-wave tests, and large scaled-plate load test for evaluating capacity. In addition to the field studies in the Woljunggyo bridge, 3-D finite element analysis was also conducted. Based on the results of the site investigation and the numerical analysis, it was concluded that the further ground improvement to build the piers was not necessary so that the gravels were placed and leveled underneath the existing pier stones to compensate partial settlement before the restoration. 신라의 수도인 경주에 서기 760년에 건설된 것으로 알려진 월정교에 대한 복원공사가 최근 완료되었다. 고문헌에 따르면, 월정교는 축조 이후 고려시대인 서기 1280년까지 약 520년 동안 사용된 것으로 보인다. 월정교지에서는 양측 교대와 4개의교각기초 및 한두단의 교각석이 발견되었다. 발견된 교각기초 중 하나는 상당한 부등침하가 일어난 상태였다. 따라서 월정교의안전한 복원을 위해서는 부등침하의 원인을 밝히는 것이 매우 중요하다. 이에 본 연구에서는 월정교 복원공사에 앞서, 지층상태 파악을 위한 시추조사, 2차원 지반강성 평가를 위한 표면파시험, 지지력 평가를 위한 대형평판재하시험 등 광범위한 현장조사를 수행하였다. 지반조사 결과를 바탕으로 기초안정성 평가를 위한 3차원 유한요소해석을 실시하였다. 연구결과, 월정교교각기초의 하부지반은 월정교 복원에 따른 하중에 대해 지지력 및 침하에 충분한 안전율을 가진 것으로 평가되었다. 따라서교각기초 하부지반에 대한 추가적인 보강은 필요하지 않은 것으로 판단되며, 복원에 앞서 부등침하가 발생한 교각기초 하부에자갈을 이용한 평탄화 작업은 실시할 필요가 있다.

Buckling analysis of functionally graded plates resting on elastic foundation by natural element method

J.R. Cho 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.2

Functionally graded material (FGM) has been spotlighted as an advanced composite material due to its excellent thermo-mechanical performance. And the buckling of FGM resting on elastic foundations has been a challenging subject because its behavior is directly connected to the structural safety. In this context, this paper is concerned with a numerical buckling analysis of metal-ceramic FG plates resting on a two-parameter (Pasternak-type) elastic foundation. The buckling problem is formulated based on the neutral surface and the (1,1,0) hierarchical model, and it is numerically approximated by 2-D natural element method (NEM) which provides a high accuracy even for coarse grid. The derived eigenvalue equations are solved by employing Lanczos and Jacobi algorithms. The numerical results are compared with the reference solutions through the benchmark test, from which the reliability of present numerical method has been verified. Using the developed numerical method, the critical buckling loads of metal-ceramic FG plates are parametrically investigated with respect to the major design parameters.

Wall Displacement and Ground-Surface Settlement Caused by Pit-in-Pit Foundation Pit in Soft Clays

Yuyong Sun,Hongju Xiao 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.4

The number of pit-in-pit foundation pit is increasing quickly because of the continuous utilization of underground spaces in urban areas. Based on the co-construction project of Shanghai Museum of Natural History foundation pit and Shanghai Metro Line 13 foundation pit in Shanghai, China, the deformation characteristics of pit-in-pit foundation pit are researched by field observation and centrifugal model tests. The lateral wall displacement of inner foundation pit includes global deformation caused by the outer foundation pit excavation and deflection caused by the excavation of itself. The effect of inner foundation pit excavation on the lateral wall displacement of outer foundation pit and ground-surface settlement is smaller. The two factors affecting the deformation characteristics of pit-in-pit foundation pit, the distance between inner and outer foundation pits (D) and the excavation width of inner foundation pit (Win), are analyzed by centrifugal model tests. The result shows that the maximum lateral wall displacements of inner and outer foundation pits decrease nearly linearly with the increase of D, but increase with the increase of Win.

Study on Damage of Shallow Foundation Building Caused by Surface Curvature Deformation in Coal Mining Area

Xiaopeng Liu,Guangli Guo,Huaizhan Li 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.11

Coal mining can lead to various forms of surface deformation, the damage caused by curvature deformation is the most extensive, which has become the key to restricting the development and utilization of coal resources under villages. Therefore, it is very important to master the deformation and destruction mechanism of buildings under surface curvature deformation for the rational exploitation of coal resources under villages. In this paper, the deformation and damage of buildings caused by curvature deformation are studied with theoretical analysis and numerical simulation, aiming at the shallow foundation building in rural China, and the following objectives are achieved: 1) Based on the theory of elastic foundation beam, the longitudinal and transverse walls are considered as a whole and analyzed, and a mathematical model of the cooperative deformation in building walls under surface curvature deformation is established. 2) The failure mechanism of masonry buildings is analyzed, including the distribution of internal stress and the form of wall cracks. 3) The influence of various factors on the internal stress changes of buildings is discussed. 4) The results of numerical simulation of wall stress distribution are similar to theoretical analysis, and the influence of doors and windows on the additional stress distribution is analyzed emphatically. This study can provide important guidance for the optimization of coal mining design under villages and the protection of village buildings.