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Random Finite Element Analysis on Cement-treated Soil Layer 随机有限元 水泥处...

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YONLIU 发表于 2016-1-7 11:21:19 | 显示全部楼层 |阅读模式
本帖最后由 三T上人 于 2016-7-22 10:47 编辑 <br /><br />SUMMARY
A layer ofimproved soil consisting of short overlapping soil-cement columns that areformed by deep mixing method or jet grouting is often used to stabilize anexcavation in soft soil (e.g., Tanaka, 1993; O’Rourke and McGinn, 2006). Theimproved soil layer is often installed prior to excavation and below theexcavation formation level. It resists lateral compression from the inwardsmoving retaining wall as excavation proceeds. Thus, rational evaluations oflateral bearing capacity and stiffness of the slab as a mass are of practicalimportance in an excavation.
In thisthesis, spatial variability of cement-treated soils is investigated and itsinfluences on the lateral mass behaviour of the layer are analyzed by numericalsimulations. The spatial variability is resolved into three categories: (1) adeterministic trend in strength along the radial direction, which is describedby a deterministic function of radial distance, (2) a stochastic fluctuationportion around the deterministic trend, which is simulated by three-dimensionalrandom fields and (3) positioning error in installation columns, which refersto the deviation of column centres from their designed positions due to theoff-verticality in pile drilling.
In thisstudy, a modified linear estimation method has been proposed to generate normalrandom fields. The proposed method has been shown to be able to generate alarge multi-dimensional property field that is both normally distributed andweakly stationary. The simulated property field is also shown to be ergodicboth in the mean and correlation as long as the property field has a finiteautocorrelation length along each direction. The proposed method can also beextended to a cylindrical field with orthogonal stationary. For a cylindricalfield, the simulated autocorrelation function along the circumferentialdirection is a monotonically decreasing function in the interval [0, π].
The spatialvariability of cement-treated soils is examined based on field data,experimental data and existing publications. The ranges of some statisticalparameters are assessed: (a) The coefficient of variation of unconfinedcompressive strength generally ranges from 0.1 to 0.5. (b) The unconfinedcompressive strength is usually positively skewed, whereas some field data showthat it may also be negatively skewed. (c) The autocorrelation length ofunconfined compressive strength in the horizontal direction is generally lessthan 30 cm. This is supported by both centrifuge and field data. (d) TheYoung’s modulus and unconfined compressive strength is positively correlatedwith a correlation coefficient generally larger than 0.79.
An improvedsoil layer involving more than 160 overlapping soil-cement columns isnumerically simulated by using random finite element method. The random fieldsfor the columns are generated using the modified linear estimation method.Three sources of heterogeneity contributing to the variability in strength andstiffness of cement-treated soils are considered in the random finite elementmethod; that is, the radial variation (i.e., deterministic trend) in stiffnessand strength, the stochastic fluctuation about the deterministic trend and thepositioning error caused by the off-verticality in pile drilling. A detailedparametric study has been conducted on the various factors in these threesources of heterogeneity affecting the mass behaviour based on the ranges ofparameters estimated from centrifuge and field data.
A detailedset of design guidelines has been proposed based on the results of randomfinite element analyses. The equivalent working stiffness and failure stress ofa soil slab can be estimated based on the design guidelines. Design values ofstiffness and failure stress can then be evaluated based on those equivalentvalues according to a target reliability index or percentile in confidence.


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Random Finite Element Analysis on Cement-treated Soil Layer 随机有限元.pdf

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东南西北人 发表于 2016-1-7 12:51:47 | 显示全部楼层
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w3w3w3 发表于 2016-2-19 21:31:27 | 显示全部楼层
本帖最后由 三T上人 于 2016-7-22 10:47 编辑 <br /><br />随机有限元吧,这个名字用random 不如Stochastic 贴切

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为什么Random 不然 Stochastic 贴切? 请赐教、、、  详情 回复 发表于 2016-3-1 16:58
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sdjzuzdh 发表于 2016-2-20 08:34:39 | 显示全部楼层

回帖奖励 +3 金币金币

本帖最后由 三T上人 于 2016-7-22 10:47 编辑 <br /><br />谢谢提供分享

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 楼主| YONLIU 发表于 2016-3-1 16:58:32 | 显示全部楼层
本帖最后由 三T上人 于 2016-7-22 10:47 编辑 <br /><br />随机有限元吧,这个名字用random 不如Stochastic 贴切[/quote]
为什么Random 不然 Stochastic 贴切? 请赐教、、、

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davidlau1976 发表于 2016-3-2 00:23:40 | 显示全部楼层
本帖最后由 三T上人 于 2016-7-22 10:47 编辑 <br /><br />

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