scholarly journals An approach for modelling spatial variability in permeability of cement-admixed soil

2021 ◽  
Author(s):  
Hardy Yide Kek ◽  
Yutao Pan ◽  
Yannick Choy Hing Ng ◽  
Fook Hou Lee
Keyword(s):  
Spatial Variability ◽  
One Dimensional ◽  
Variable Permeability ◽  
Coefficient Of Permeability ◽  
Scale Of Fluctuation ◽  
Random Finite Element Method ◽  
Consolidation Rate ◽  
Parametric Studies ◽  
Strength Variability ◽  
Random Finite Element

AbstractThis paper presents a framework for modelling the random variation in permeability in cement-admixed soil based on the binder content variation and thereby relating the coefficient of permeability to the unconfined compressive strength of a cement-admixed clay. The strength–permeability relationship was subsequently implemented in random finite element method (RFEM). The effects of spatial variation in both strength and permeability of cement-admixed clays in RFEM is illustrated using two examples concerning one-dimensional consolidation. Parametric studies considering different coefficient of variation and scale of fluctuation configurations were performed. Results show that spatial variability of the cement-admixed clay considering variable permeability can significantly influence the overall consolidation rate, especially when the soil strength variability is high. However, the overall consolidation rates also depend largely on the prescribed scales of fluctuation; in cases where the variation is horizontally layered, stagnation in pore pressure dissipation may occur due to soft parts yielding.

scholarly journals On Two Approaches to Slope Stability Reliability Assessments Using the Random Finite Element Method

2019 ◽  
Vol 9 (20) ◽  
pp. 4421 ◽  
Author(s):  
Yajun Li ◽  
Cheng Qian ◽  
Zhongzhi Fu ◽  
Zhuo Li
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Spatial Variability ◽  
Search Algorithm ◽  
Strength Properties ◽  
Global Factor ◽  
Random Finite Element Method ◽  
Random Finite Element ◽  
Soil Spatial Variability ◽  
Element Method

The random finite element method has been increasingly used in the geotechnical community to investigate the influence of soil spatial variability and to bridge the gap between a traditional design and a reliability-based design. There are two approaches to calculate the reliability curves as a function of the traditional/global factor of safety in the literature. However, it is not clear how these two approaches may be related and why. This paper is devoted to answering this question, through the aid of an implemented auto-search algorithm within the strength reduction method and the quantification of the potential sliding volumes in the various possible Monte Carlo realisations of the soil spatial variability. The equivalences and differences between the two approaches, and thereby their respective merits and disadvantages, are explained and discussed for the most commonly used distribution types of soil strength properties, that is, normal and lognormal distribution. Computational efficiency has also been addressed in the form of pseudocodes, which can be readily implemented.

scholarly journals Probabilistic Bearing Capacity of a Pavement Resting on Fibre Reinforced Embankment Considering Soil Spatial Variability

2021 ◽  
Vol 7 ◽  
Author(s):  
Kouseya Choudhuri ◽  
Debarghya Chakraborty
Keyword(s):  
Spatial Variability ◽  
Soil Properties ◽  
Bearing Capacity ◽  
Coefficient Of Variation ◽  
Friction Angle ◽  
Horizontal Scale ◽  
Vertical Scale ◽  
Scale Of Fluctuation ◽  
The Mean ◽  
The Finite Difference Method

This paper intends to examine the influence of spatial variability of soil properties on the probabilistic bearing capacity of a pavement located on the crest of a fibre reinforced embankment. An anisotropic random field, in combination with the finite difference method, is used to carry out the probabilistic analyses. The cohesion and internal friction angle of the soil are assumed to be lognormally distributed. The Monte Carlo simulations are carried out to obtain the mean and coefficient of variation of the pavement bearing capacity. The mean bearing capacity of the pavement is found to decrease with the increase in horizontal scale of fluctuation for a constant vertical scale of fluctuation; whereas, the coefficient of variation of the bearing capacity increases with the increase in horizontal scale of fluctuation. However, both the mean and coefficient of variation of bearing capacity of the pavement are observed to be increasing with the increase in vertical scale of fluctuation for a constant horizontal scale of fluctuation. Apart from the different scales of fluctuation, the effects of out of the plane length of the embankment and randomness in soil properties on the probabilistic bearing capacity are also investigated in the present study.

Random finite element method for the seismic analysis of gravity dams

2018 ◽  
Vol 171 ◽  
pp. 405-420 ◽  
Author(s):  
M.A. Hariri-Ardebili ◽  
S.M. Seyed-Kolbadi ◽  
V.E. Saouma ◽  
J. Salamon ◽  
B. Rajagopalan
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Seismic Analysis ◽  
Gravity Dams ◽  
Random Finite Element Method ◽  
Random Finite Element ◽  
Element Method

scholarly journals Spatial Variability Pattern of Hyporheic Exchange in a braided River

2018 ◽  
Vol 246 ◽  
pp. 01098
Author(s):  
Guangdong Wu ◽  
Xiao Zhang ◽  
Jijun Xu
Keyword(s):  
Spatial Variability ◽  
Flow System ◽  
Hyporheic Exchange ◽  
Braided River ◽  
Downward Flow ◽  
One Dimensional ◽  
Physical Mechanisms ◽  
Braided Channel ◽  
Variability Pattern ◽  
Heat As A Tracer

The streambed flux is variable in space; the spatial variability results in part from bedforms, but few works on streambed fluxes in channels with strongly abrupt varying bedforms are carried out. Heat as a tracer to delineate the streambed flux pattern has been widely adopted in numerous fields. In this paper, a braided channel with complicated topography was selected as study site, where the temperature was monitored. One-dimensional (1-D) analytical method based on the amplitude attenuation (Ar) and 1-D numerical method were used to interpret the temperature. As a result, streambed fluxes of a total of 50 sites in the braided channel are obtained. From the results we can know the magnitude and direction of streamed flow velocity are spatially variable, even within a 1-m distance. Then, this study summarizes five bedform-driven flux patterns: ① downward flow driven by the head difference between groundwater and stream, ② downward flow related to a meter-scale pool, ③ a transition from upward to downward flow associated with a centimeter-scale riffle, ④ horizontal flow in braided bars and ⑤ upward flow driven by vegetation roots. Overall, multiple physical mechanisms together contributed to the complex streambed flow system, which reflected great challenges for the scaling up of point-in-space seepage flux.

Characteristic strength of soils underlying foundations considering effect of spatial variability

2020 ◽  
Vol 57 (4) ◽  
pp. 518-536
Author(s):  
Guicai Shi ◽  
Yutao Pan ◽  
Zhaohua Sun ◽  
Yong Liu ◽  
Fook-Hou Lee
Keyword(s):  
Spatial Variability ◽  
Bearing Capacity ◽  
Reduction Factor ◽  
Failure Zone ◽  
Strength Reduction Factor ◽  
Average Strength ◽  
Characteristic Strength ◽  
Random Finite Element ◽  
Weak Zones ◽  
Local Average

In Eurocode EC7, a “characteristic” strength is used as a cautious estimate of the local average strength that governs the bearing capacity of the foundation. The objective of this paper is to examine the correlation between the local average strength and the bearing capacity of a stiff caisson foundation resting on spatially variable ground using random finite element analyses. The results show that using the local average strength over some assumed or postulated failure zones tends to overestimate the mean bearing capacity of the ground. This can be attributed to two possible reasons. Firstly, the postulated failure zone is unlikely to be fully reflective of the real failure zone in spatially variable ground. Secondly, the bearing capacity is more affected by the strength of the weak zones than that of the strong zones. Both of these factors lead to a lowering of the bearing capacity. A more indicative way of determining a characteristic strength that will give a better indication of the bearing capacity is also recommended, together with a strength reduction factor that accounts for the effect of spatial variability.

Evaluation of Uncertainties of One-Directional Analytical Model for Thermoreflectance Technique

2011 ◽  
Author(s):  
Changhu Xing ◽  
Zilong Hua ◽  
Heng Ban ◽  
David Hurley ◽  
J. Rory Kennedy
Keyword(s):  
Parametric Design ◽  
Thermal Effusivity ◽  
Analytical Models ◽  
Volumetric Heating ◽  
One Dimensional ◽  
Parametric Studies ◽  
Commercial Software Package ◽  
The Difference ◽  
Lock In ◽  
General Guidance

One dimensional (1-D) analytical models are generally used for the evaluation of thermal effusivity of film or substrate in thermoreflectance measurement. However, the range of uncertainties associated with the 1-D assumptions needs to be quantified in order to determine the applicability of 1-D models. In the current study, a two-dimensional (2-D) numerical model was created in a commercial software package, COMSOL, to investigate the difference of results obtained by 1-D or 2-D models. The analysis used a frequency lock-in strategy and the result was verified by a comparison of 1-D numerical simulation to 1-D theoretical values. Parametric studies were performed by considering film thickness, heating laser radius, volumetric heating, thermal resistance between layers, and anisotropic thermal conductivities. The results and conclusions provide a general guidance and reference for the parametric design of thermoreflectance measurements.

Sign in / Sign up

Export Citation Format

Share Document