scholarly journals Pseudo-static Simplified Analysis Method of the Pile-liquefiable Soil Interaction Considering Rate-dependent Characteristics

2021 ◽  
Author(s):  
Xinlei Zhang ◽  
Zhanpeng Ji ◽  
Hongmei Gao ◽  
Zhihua Wang ◽  
Wenwen Li
Keyword(s):  
Interaction Analysis ◽  
Bending Moment ◽  
Viscosity Coefficient ◽  
Excess Pore Pressure ◽  
Shear Strain Rate ◽  
Rate Dependent ◽  
Liquefiable Soil ◽  
Viscous Shear ◽  
Pile Interaction ◽  
Simplified Analysis

The lateral pressure generated by liquefied soil on pile is a critical parameter in the analysis of soil-pile interaction in liquefaction-susceptible sites. Previous studies have shown that liquefied sand behaves like a non-Newton fluid, and its effect on piles has rate-dependent properties. In this study, a simplified pseudo-static method for liquefiable soil-pile interaction analysis is proposed by treating the liquefied soil as a thixotropic fluid, which considers the rate-dependent behavior. The viscous shear force generated by the relative movement between the viscous fluid (whose viscosity coefficient varies with excess pore pressure and shear strain rate) and the pile was assumed to be the lateral load on the pile. The results from the simplified analysis show that the distribution of bending moment is in good agreement with experiments data. Besides, the effects of various parameters, including relative density, thickness ratio of non-liquefiable layer to liquefiable layer, and frequency of input ground motion, on the pile-soil rate-dependent interaction were discussed in detail.

scholarly journals Sustainable Measures for Protection of Structures Against Earthquake Induced Liquefaction

2021 ◽  
Author(s):  
Gopal S. P. Madabhushi ◽  
Samy Garcia-Torres
Keyword(s):  
Soil Liquefaction ◽  
Excess Pore Pressure ◽  
Economic Losses ◽  
Element Analysis ◽  
Centrifuge Testing ◽  
Centrifuge Tests ◽  
Liquefiable Soil ◽  
Recent Earthquakes ◽  
Excess Pore Pressures ◽  
Excess Pore

AbstractSoil liquefaction can cause excessive damage to structures as witnessed in many recent earthquakes. The damage to small/medium-sized buildings can lead to excessive death toll and economic losses due to the sheer number of such buildings. Economic and sustainable methods to mitigate liquefaction damage to such buildings are therefore required. In this paper, the use of rubble brick as a material to construct earthquake drains is proposed. The efficacy of these drains to mitigate liquefaction effects was investigated, for the first time to include the effects of the foundations of a structure by using dynamic centrifuge testing. It will be shown that performance of the foundation in terms of its settlement was improved by the rubble brick drains by directly comparing them to the foundation on unimproved, liquefiable ground. The dynamic response in terms of horizontal accelerations and rotations will be compared. The dynamic centrifuge tests also yielded valuable information with regard to the excess pore pressure variation below the foundations both spatially and temporally. Differences of excess pore pressures between the improved and unimproved ground will be compared. Finally, a simplified 3D finite element analysis will be introduced that will be shown to satisfactorily capture the settlement characteristics of the foundation located on liquefiable soil with earthquake drains.

Centrifuge Modeling on Seismic Behavior of Pile in Liquefiable Soil Ground

2013 ◽  
Vol 479-480 ◽  
pp. 1139-1143
Author(s):  
Wen Yi Hung ◽  
Chung Jung Lee ◽  
Wen Ya Chung ◽  
Chen Hui Tsai ◽  
Ting Chen ◽  
...  
Keyword(s):  
Seismic Behavior ◽  
Soil Structure ◽  
Lateral Displacement ◽  
Bending Moment ◽  
Soil Liquefaction ◽  
Centrifuge Modeling ◽  
Shaking Table ◽  
Pile Head ◽  
Liquefiable Soil ◽  
Tip Mass

Dramatic failure of pile foundations caused by the soil liquefaction was founded leading to many studies for investigating the seismic behavior of pile. The failures were often accompanied with settlement, lateral displacement and tilting of superstructures. Therefore soil-structure interaction effects must be properly considered in the pile design. Two tests by using the centrifuge shaking table were conducted at an acceleration field of 80 g to investigate the seismic response of piles attached with different tip mass and embedded in liquefied or non-liquefied deposits during shaking. It was found that the maximum bending moment of pile occurs at the depth of 4 m and 5 m for dry sand and saturated sand models, respectively. The more tip mass leads to the more lateral displacement of pile head and the more residual bending moment.

Seismic Response of Pile Groups Improved with Deep Cement mixing Columns in Liquefiable Sand: Shaking Table Tests

2021 ◽  
Author(s):  
Dingwen Zhang ◽  
Anhui Wang ◽  
Xuanming Ding
Keyword(s):  
Seismic Behavior ◽  
Lateral Displacement ◽  
Bending Moment ◽  
Pile Group ◽  
Shaking Table ◽  
Excess Pore Pressure ◽  
Shaking Table Tests ◽  
Pile Groups ◽  
Acceleration Response ◽  
Table Model

A series of shaking table model tests were performed to examine the effects of deep cement mixing (DCM) columns with different reinforcement depths on the seismic behavior of a pile group in liquefiable sand. Due to the DCM column reinforcement, the fundamental natural frequency of the model ground increases noticeably. The excess pore pressure of soils reduces with the increase of reinforcement depths of the DCM columns. Before liquefaction, the acceleration response of soils in the improved cases is obviously lower than that in the unimproved case, but the acceleration attenuation is greater after liquefaction in the unimproved case. Moreover, the lateral displacement of the superstructure, the settlement of the raft, and the bending moment of the piles in the improved cases are significantly reduced compared to those in the unimproved case, and the reduction ratios rise with the increase of reinforcement depth of the DCM columns. However, reinforcement by the DCM columns may result in the variation of the location of the maximum moment that occurs in the pile.

scholarly journals Uplifting Behavior of Shallow Buried Pipe in Liquefiable Soil by Dynamic Centrifuge Test

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Bo Huang ◽  
Jingwen Liu ◽  
Peng Lin ◽  
Daosheng Ling
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Earth Pressure ◽  
Soil Liquefaction ◽  
Excess Pore Pressure ◽  
Buried Pipe ◽  
Seismic Surveys ◽  
Underground Pipelines ◽  
Liquefiable Soil ◽  
Centrifuge Model Tests

Underground pipelines are widely applied in the so-called lifeline engineerings. It shows according to seismic surveys that the damage from soil liquefaction to underground pipelines was the most serious, whose failures were mainly in the form of pipeline uplifting. In the present study, dynamic centrifuge model tests were conducted to study the uplifting behaviors of shallow-buried pipeline subjected to seismic vibration in liquefied sites. The uplifting mechanism was discussed through the responses of the pore water pressure and earth pressure around the pipeline. Additionally, the analysis of force, which the pipeline was subjected to before and during vibration, was introduced and proved to be reasonable by the comparison of the measured and the calculated results. The uplifting behavior of pipe is the combination effects of multiple forces, and is highly dependent on the excess pore pressure.

scholarly journals Study on Seismic Response in Deeply Deposited Saturated Liquefiable Soil Reinforced by Using Subarea Long-Short Gravel Piles

2021 ◽  
Vol 11 (23) ◽  
pp. 11271
Author(s):  
Junding Liu ◽  
Rongjian Li ◽  
Shibin Zhang ◽  
Weishi Bai ◽  
Ze Li
Keyword(s):  
Seismic Response ◽  
Underlying Mechanism ◽  
Dynamic Responses ◽  
Shielding Effect ◽  
Excess Pore Pressure ◽  
Reinforcement Scheme ◽  
Total Length ◽  
Liquefiable Soil ◽  
Natural Foundation ◽  
Excess Pore

To avoid large deformation, resulting from liquefaction, in inclined and deeply deposited liquefiable soil, it is necessary to design economical and reasonable reinforcement schemes. A reinforcement scheme employing subarea long-short gravel piles was proposed, and it was successfully applied in the embankment construction of the Aksu-kashgar highway. To reveal its underlying mechanism and effect on the seismic performance of the highway, the dynamic responses of natural foundation and two kinds of reinforced foundations were analyzed and compared under this scheme, using the program FEMEPDYN. Results showed that both the seismic subsidence and the excess pore pressure ratios were far less in the foundation reinforced with isometric gravel piles and in the foundation reinforced with subarea long-short gravel piles, compared with that in natural foundation. Therefore, the potential hazards of liquefaction were overcome in these two kinds of reinforced foundations. Furthermore, it was obvious that the shielding region only formed within the foundation reinforced with subarea long-short gravel piles. With the shielding effect, the proposed reinforcement scheme employing subarea long-short gravel piles not only eliminated liquefaction in deeply deposited liquefiable soil, but it also demonstrated an outstanding advantage in that the total length of gravel piles used was greatly reduced compared to the total length in the isometric gravel piles scheme and the interphase long-short gravel piles.

scholarly journals Influence of Soil Liquefaction on the Structural Performance of Bridges During Earthquakes: Showa Bridge as A Case Study

2018 ◽  
Vol 7 (4.20) ◽  
pp. 146
Author(s):  
Mohammed K. Dhahir ◽  
Wissam Nadir ◽  
Mohammed H. Rasool
Keyword(s):  
Lateral Displacement ◽  
Bending Moment ◽  
Sandy Soils ◽  
Soil Liquefaction ◽  
Shallow Foundations ◽  
Structural Performance ◽  
Excess Pore Pressure ◽  
Regular Structures ◽  
Loss Of Contact

Liquefaction is generally defined as the loss of contact between soil particles during shaking (earthquakes), and it usually occurs in saturated loose sandy soils where the timescale is insufficient for the water to drain from the pores, thus increasing the excess pore pressure, and thereby floating the sand particles. For regular structures with shallow foundations, liquefaction normally leads to loss of soil strength, which leads to settlement of foundations. On the other hand, bridges are usually supported with piles foundation, which introduces additional effects during liquefaction. Therefore, this paper examines the possible effects of liquefaction on the structural performance of bridges during earthquakes. Furthermore, the failure of Showa Bridge during the 1964 Nagata earthquake was also discussed and analyzed as an example of the catastrophic effects of liquefaction. The analysis shows that the most influential effect during liquefaction is the increase in the unsupported length of piles, which leads to several adverse effects such as increasing the lateral displacement, reduce the buckling capacity, increase the bending moment, and reduce the shaft capacity of the pile. Finally, recommendations regarding the design of pile supported bridges in seismic areas with liquefiable soils have also been suggested. 

scholarly journals Simplified analysis of large deflections for metal sandwich plates with various lattice cores subjected to impulsive loading

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401878740
Author(s):  
Wei Zhang ◽  
Qinghua Qin ◽  
Jianxun Zhang ◽  
Shangjun Chen ◽  
Zili Xu
Keyword(s):  
Structural Response ◽  
Yield Condition ◽  
Bending Moment ◽  
String Model ◽  
Impulsive Loading ◽  
Sandwich Plates ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Simplified Analysis ◽  
Sandwich Core

A new simplified analysis is carried out to predict the dynamic response of clamped metal sandwich plates with various lattice cores subjected to impulsive loading. Based on the yield condition for sandwich plate cross-section, the interaction of bending moment and axial force for the section is decoupled. The simplified analytical solutions of the maximum midspan deflection and structural response time are obtained. Moreover, neglecting the effect of bending moment, a simplified plastic-string model is developed. Comparisons of the present theoretical predictions with previous analytical and numerical results are conducted and good agreement is achieved for a wide range of sandwich core topologies.

Simplified, Detailed, and Isochronous Analysis and Test Results for the In-Plane Elastic-Plastic and Creep Behavior of an Elbow

1986 ◽  
Vol 108 (3) ◽  
pp. 297-304 ◽  
Author(s):  
L. H. Sobel ◽  
S. Z. Newman
Keyword(s):  
Creep Behavior ◽  
Bending Moment ◽  
Time Dependent ◽  
304 Stainless Steel ◽  
Plastic Behavior ◽  
Test Results ◽  
Creep Properties ◽  
Elastic Plastic ◽  
Creep Analysis ◽  
Simplified Analysis

Predictions obtained from simplified and detailed MARC analyses are compared with experimental results for the elastic-plastic and creep behavior of a 16-in-dia 304 stainless steel piping structure subjected to an in-plane closing bending moment. The piping structure is composed of a 90-deg elbow and two straight tangent pipes. The simplified analysis is found to considerably overestimate the measured results, especially for the case of creep behavior. The correlation of detailed analysis predictions with measured results is satisfactory for the elastic-plastic behavior of the structure, and inconclusive for the creep behavior, since the creep predictions are based on a commonly used creep law rather than on the actual (but unmeasured) creep properties. The paper also shows that predictions of creep deformation obtained from the relatively inexpensive time-independent isochronous method of analysis agree well with results given by a “complete” and more costly time-dependent creep analysis.

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