Capacity of shallow foundations on saturated cohesionless soils under combined loading

2009 ◽  
Vol 46 (6) ◽  
pp. 639-649 ◽  
Author(s):  
M. Tolga Yilmaz ◽  
B. Sadik Bakir
Keyword(s):  
Stress Path ◽  
Reduction Factor ◽  
Shallow Foundations ◽  
Combined Loading ◽  
Saturated Soils ◽  
Soil Behavior ◽  
Seismic Capacity ◽  
Moment Capacity ◽  
Overturning Moment ◽  
The Impact

Under seismically induced loading, shallow foundations commonly fail by overturning on saturated soils. While the excess pore pressures may have fully dissipated following construction, undrained conditions are typically presumed in the assessment of seismic capacity in conventional applications due to the high rates of loading induced during an earthquake. Undrained strength, however, can be critically dependent on the history of loading and significantly heterogeneous and anisotropic around a foundation. The finite element method is utilized in this study for a proper assessment of the impact of these factors on the overturning moment capacity of surficial foundations on saturated soils, with specific emphasis on failure under seismic loading. Uplift capability has been incorporated into the models and analyses have been conducted for different drainage conditions. Based on the analyses results and comparisons with analytical formulae, it is concluded that the assumption of homogeneous soil strength as well as the disregard of stress path followed can lead to significant overestimation of the overturning moment capacity. The proposed improved approach comprises calculation of the overturning moment capacity based on drained soil behavior and subsequent application of an undrained behavior reduction factor (URF) compatible with the representative pore-pressure parameter A.

Adding Ash Methane Oxidation in Landfill Cover Soil Research

2014 ◽  
Vol 926-930 ◽  
pp. 4205-4208
Author(s):  
Yan Li Wu ◽  
Qing Feng Zhang ◽  
Ran Zhuo Zhang ◽  
Xiao Ming Mao ◽  
Xin Hua Sun
Keyword(s):  
Methane Oxidation ◽  
Chemical Properties ◽  
Soil Surface ◽  
Soil Behavior ◽  
Soil Microbial ◽  
Landfill Cover Soil ◽  
Landfill Cover ◽  
Cover Soil ◽  
Physical And Chemical ◽  
The Impact

In the past ten years, methane has a greenhouse gas, and its concentration increases by 1% per year, while an estimated worldwide annual landfill cover soil surface from escaping methane is about 20 to 70 Mtpa. Microbial methane oxidation can be carried out about 80% of global consumption of methane, the soil microbial methane oxidation can reduce methane escaping from the soil to the atmosphere. Both in domestic and foreign ash recycling in landfill cover soil behavior has performed for many years, but there is a review of domestic and foreign literature ash, mostly looks at the aspects of physical and chemical properties and heavy metals, there is no assessment of the casing methane oxidation impact. This paper mainly urban incinerator ash as a research object, and after a landfill cover soil mined to study experimentally analyze the impact of ash added methane oxidation right.

Modified state-surface approach to the study of unsaturated soil behavior. Part I: Basic concept

2009 ◽  
Vol 46 (5) ◽  
pp. 536-552 ◽  
Author(s):  
Xiong Zhang ◽  
Robert L. Lytton
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Stress Path ◽  
Complex Stress ◽  
Soil Behavior ◽  
Elastic Surface ◽  
Surface Approach ◽  
Basic Model ◽  
Plastic Hardening ◽  
Complex Stress Path

The traditional state-surface approach to the study of unsaturated soil behavior is becoming much less popular these days, as it uses unique constitutive surfaces to represent unsaturated soil behavior. This approach is essentially a nonlinear elastic formation and cannot be used to explain complex stress-path dependency for unsaturated soils. In this paper, a modified state-surface approach (MSSA) is proposed to represent unsaturated soil behavior under isotropic stress conditions in which a conventional void-ratio state surface is considered to be made up of an elastic surface and a plastic hardening surface. The plastic hardening surface remains stationary at all times, whereas the elastic surface remains unchanged when the soil experiences elastic deformation and moves downward when there is plastic hardening occurrence. Using the MSSA, the loading–collapse (LC) and the suction increase (SI) yield curves in the Barcelona basic model (BBM) are derived. The prediction of three typical cases of soils under isotropic conditions and experimental results using the proposed approach confirmed its feasibility, simplicity, and potential for the study of unsaturated soil behavior.

Influence of Initial Anisotropy, Stress Path and Principal Stress Rotation on Monotonic Behavior of Clean and Mixed Sands

2020 ◽  
Vol 857 ◽  
pp. 417-430
Author(s):  
Kazem Fakharian ◽  
Farzad Kaviani Hamedani
Keyword(s):  
Principal Stress ◽  
Stress Path ◽  
Silica Sand ◽  
Large Strains ◽  
Principal Stress Rotation ◽  
Soil Behavior ◽  
Stress Rotation ◽  
Fabric Evolution ◽  
Initial Anisotropy

It is widely accepted that soil behavior is complicated taking into account soil anisotropy owing to the fact that this phenomenon arises from oriented soil fabric or structure forged in the deposition stage. In this study, a review of major findings of authors’ previous studies are presented with the main focus on soil anisotropy using extensive experimental results incuding Triaxial (TXT), Simple Shear (SSA), and Hollow Cylinder (HCA) apparatus. Effects of initial anisotropy, fabric evolution, stress path, principal stress rotation and intermediate stress state are evaluated for a crushed silica sand. In addition, the effects of Portland cement content and granulated rubber contents on anisotropic behavior of the sand are investigated. Bender elments are mounted on triaxial specimens both in vertical and horizontal directions to measure the shear wave velocity and hence maximum shear modulus at the end of consolidation as well as during shearing up to large strains at critical state condition, as an index of evaluating the fabric evolution. The effects of principal stress rotation and stress paths reveals the crucial role of soil anisotropy on the behavior of clean sand. However, adding either cement or granulated rubber to the sand has considerably decreased anisotropy.

A Simple and Practicable Approach on Implementing for the Reduced Triaxial Extension by the Conventional Triaxial Apparatus

2011 ◽  
Vol 250-253 ◽  
pp. 2089-2092
Author(s):  
Rong Jian Li ◽  
Xi An Li ◽  
Gao Feng Che ◽  
Wen Zheng ◽  
Wen Jun Chen
Keyword(s):  
Triaxial Compression ◽  
Stress Path ◽  
Test Results ◽  
Triaxial Apparatus ◽  
Eolian Sand ◽  
Conventional Triaxial Compression ◽  
The Difference ◽  
Shear Behaviors ◽  
The Impact ◽  
Triaxial Extension

Stress path is one of the very important factors of soil strength. It is significant to study the strength and reveal the importance of the impact of sand in different stress path conditions. Firstly, an ameliorating approach on implementing for the reduced triaxial extension by the conventional triaxial apparatus was discussed. Then, In order to study shear behaviors of the eolian sand under different stress path, two monotonic shearing tests with the conventional triaxial compression and the reduced triaxial extension stress path were performed and analyzed. The test results not only indicate that the amelioration on conventional triaxial apparatus is simple, practicable and inexpensive, but also reveal the difference of strength’s parameter between the reduced triaxial extension and conventional triaxial compression stress path. In sum, the stress path has important effect on the strength of the eolian sand.

Centrifuge Simulation of Wave Propagation due to Vertical Vibration on Shallow Foundations and Vibration Attenuation Countermeasures

2005 ◽  
Vol 11 (6) ◽  
pp. 781-800 ◽  
Author(s):  
K. Itoh ◽  
X. Zeng ◽  
M. Koda ◽  
O. Murata ◽  
O. Kusakabe
Keyword(s):  
Wave Propagation ◽  
High Speed ◽  
Ground Vibration ◽  
Vertical Vibration ◽  
Shallow Foundations ◽  
Testing System ◽  
High Speed Trains ◽  
Railway System ◽  
Environmental Consideration ◽  
The Impact

When constructing a high-speed railway system in an urban area, the reduction of the ground vibration and noise generated by train passages is a vitally important environmental consideration. In this paper we focus on the development of a centrifuge vibration testing system, which can simulate dynamic loading acting on shallow foundations. The system is used to generate vertical vibration similar to that generated by high-speed trains. The characteristics of wave propagation in a shallow circular foundation on sand are investigated. The effects of two types of barriers on vibration reduction are studied. Additionally, the impact of using vibration attenuating materials to build trackbeds is evaluated.

The Studies of Rock Damage Softening Statistical Constitutive Model under True Triaxial Stress State

2014 ◽  
Vol 580-583 ◽  
pp. 312-315
Author(s):  
Hui Mei Zhang ◽  
Xiang Miao Xie ◽  
Geng She Yang
Keyword(s):  
Constitutive Model ◽  
Strain Curve ◽  
Stress Path ◽  
Complex Stress ◽  
Model Parameters ◽  
Stress Strain ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Complex Stress Path ◽  
The Impact

From the feature of rock micro-unit failure obeys Poisson random distribution, the damage softening statistical constitutive of was established under true triaxial confinement based on D-P criterion, so the impact of the intermediate principal stress on rock deformation and failure was considered in theory, and the actual engineering rock complex stress path evolution was reflected more realistically. Furthermore, according to the geometrical conditions of stress-strain relationship, the theoretical relationship between constitutive model parameters and the stress-strain curve characteristic parameters during the process of rock softening and deforming, which enhance the adaptability of the model. Finally, the rationality of the model verified by the measured data.

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