土木工程外文翻译--软土地基上分期施工的路堤沉降预测方法

土木工程外文翻译--软土地基上分期施工的路堤沉降预测方法
土木工程外文翻译--软土地基上分期施工的路堤沉降预测方法

Settlement prediction of embankments with stage

LIU Song-yu(Institute of Geotechnical Engineering, Southeast University,Nanjing 210096,China)JING Fei(Institute of Geotechnical Engineering, Southeast University,Nanjing 210096,China)

Abstract: The magnitude and rate of the settlement are the key elements subjected to design analysis of embankments on soft ground. The observational

Institute of Geotechnical Engineering,Southeast University,Nanjing210096,China methods based onfield measurement have indicated the promising results and become effective methods to predict the final settlement, while the uncertainties of parameters and theories limit significantly the accuracy of settlement estimation. This paper presents an observational method to predict the settlement performance of embankments with stage construction on soft ground based on Asaoka method. The case studies show the accordance of the predicting results with the field measured data. It is also given from the case study that the value of E u / C u ratio ranges from 50 to 100 for Jiangsu Marine clay and its actual coefficient of consolidation is almost one order of magnitude larger than the laboratory data.

Key words:settlement, embankment, observational method, stage construction 1. Introduction

Settlement and stability are two primary considerations systematically related to the design of an embankment on soft ground. The tools available for the stability evaluation seem to be satisfactory. The key element of long term behavior of the embankment routinely subjected to design analysis is the settlement. In other words , the settlement analysis is the most appropriate approach to the embankment analysis .

The settlements of embankments on soft clays result from the consolidation and the lateral flow under the embankments. Many researches have been made on performance of embankments on soft ground.

Although many experiences have shown the practical value of the theory for estimating settlements and settlements rates , they also illustrated some of the problems in volved in making accurate prediction of the settlement .Duncan (1993) and Olson (1998) analyzed the uncertainties causing the shortcomings in the current state of the art for settlement prediction respectively. These uncertainties sometimes make it difficulty or impossible to estimate the magnitude and rate of settlement for embankments . Although the numerical analysis may be possible to improve the accuracy , the soil models may involve many parameters that can not be determined economically. However , the evolution of numerical methods with computer may result in simpler models and complete codes that are increasingly becoming available.

It is desirable therefore to develop observational methods based upon which the settlement can be estimated once sufficient data has been recorded. Many researchers developed the settlement prediction methods on field measurement observation , which have indicated promising results and become an accepted method to estimate final settlements and rates of settlements.

Stage construction is a typical procedure for embankments on the soft ground. With a certain period of consolidation at every stage construction ,the safety factor of the embankment can be generally raised and the post construction settlement may be reduced. The settlement - time curve during stage construction may be more complicated than it is with instantaneous loading. The period for primary consolidation at a definite final load with stage construction may be increased significantly , in spite of the fact that the post construction settlement can be reduced. In order to speed up the rate of settlement and minimize the post construction secondary settlement of soft clays , surcharge is often used in practice ,which can be taken as a type of stage construction with temporary loading and unloading stages .

Problems related to the settlement analysis of stage construction for embankments on soft clays are of the following types:

(1) Prediction of the deformation behavior of stage construction from the

results of borings and tests .

(2) Prediction of the final settlement at permanent load from the behavior of the first stage construction.

(3) Prediction of the post construction settlement at the permanent load and corresponding time of surcharge removed from the behavior of the surcharge.

The first of these problems is heavily dependent on the theory , which is necessary in design. The other two predictions require empirical rather than theoretical methods because they are based on observational data. In any case , the fact that the second and third predictions are derived from field observations makes them more reliable than the theoretical predictions .

Leroueil et al revealed the effective stress path and analyzed the relationship between vertical settlement and lateral displacement during stage construction. Stamatopoulos and Kotzias developed a method to determine the final settlement at permanent load from the behavior of surcharge, but it is based on the elastic theory and difficult to calculate the rate of the settlement . The hyperbolic method is based on the total load - settlement relationship to predict the final settlement , which is not sensitive to the nature of the initial loading condition.

This paper presented a method for the prediction of the final settlement at permanent load from the behavior of the first stage construction based on the Asaoka method.

2. Stage observational method

Asaoka proposed an‘observational procedure’to estimate the final settlement and in2situ coefficient of consolidation from the field observational data. This method is becoming increasing popular because of its simplicity and effectivity.

The method is based on the fact that one dimensional consolidation settlements S0 , S1 , S2 , … ,S j at times 0 ,?t ,2?t ,… ,j?t can be expressed as a first order approximation by

which represents a straight line in a S j vs S j-1 plot , where

βis the intercept and

βis the slope of the line. When the ultimate settlement has been reached : S j= 1

S j-1=S f , therefore ,the ultimate settlement S f can be given by

and

ln 1β= -

26H t C V ? (both top and bottom drainage) ln 1β= - 22H

t C V ? (top drainage) The constant 1β has been suggested by Magnan and Deroy to be related to

the coefficient of consolidation Cv as follows: for horizontal radial drainage only for vertical drainage only

where D e , H are the drainage path length respectively.

Asaoka method also stated that the straight line in S j - S j-1 space would moved up in the case of multi-staged loading , moreover , the shifted lines become almost parallel to the initial when the settlement is relatively small compared to the thickness of clay layer. However , it is not discussed and provided how to determine the shift distance from the line of first stage to the line of the next stage.

In the expression (1) ,when j = 0 that is : t = 0 and S (t=0) = S 0 ,where t can be taken as 0 from any time after loading works . If t is set as 0 at the exact time once the load is exerted , then , S j-1 becomes 0。 This means that Asaoka method can be extended to obtain the construction settlement , which equals to the intercept 0β of the liner line in the space S j - S j-1, where t = 0 is set just after loading. Moreover , this immediate settlement contributes the shift distance of the parallel lines during stage construction.

In fact , from the derivation of the Asaoka method , the settlement of soil layers can be expressed as

and

+'++++'++=)(51)(31)(41)(21),(243242F C Z F C Z ZF T C Z T C Z T z t V

V V V !!!!ε where T and F are two unknown function of time.

With the vertical drainage boundary conditions and at the ground surface , ),(z t ε=T =ε(t , z=0) . If t = 0 , ),(z t ε=ε(t=0 , z=0) =e ε= initial elastic strain. Therefore ,

S(t=0)=S 0 gives the immediate settlement S e , which can also be estimated from the

elastic method by the equation :

It is clearly shown that the Asaoka method has been extended to predict the settlement of embankments with stage construction. In other words , the behavior of next stage construction can be predicted with the 0β ,1β from the last stage

construction. The more the previous stages with settlement measurement , the higher the accuracy of next stage prediction. The stage observational method includes following steps :

(1) Sketch observed time settlement curve .

(2) Choose a time interval ?t , which usually ranges from 10 to 100 days , read the settlements S j from the curve at times t j ( = ?t j , j = 1 ,2 ,3, …).

(3) Plot the settlements S j , S j-1 in a coordinate system with axis S j , S j-1 originated from 0.

(4) Fit the plotted points by a straight line , of which corresponding slope is read as 1β. The intercept at the S j axis gives 0β , while the point of intersection

with the 45o line , gives the final consolidation settlement of the first stage.

(5) From the 0β of the first stage construction to determine the undrained

modulus E u by inverse analysis (10) .

(6) Determine the next stage construction settlement with the above known E u

(10) , thus resulting in the shift distance of line.

(7) Assume the C V remains constant during stage construction and settlement is small compared with the thickness of soft soils , this makes the line of next stage construction parallel to the first stage with the slope 1β.

(8) Predicting the final settlement of next stage construction from the intersection of the shifted line with the 45o line.

(9) Estimate the C h and C V from the value of 1β with the equation (5) or (6) .

3. Case study

3. 1 Site and project description

Section A of Lianxu highway is a 31 km long high standard expressway connecting the port city Lianyugang to the national highway system of China. It

was began to construction from Dec. 1999. There are 104 bridges or culverts or passways in this 31 km long section designed to connect embankments . The bottom width of the embankment is 40 m , while the height of embankment changes from 3 to 7 m.

Based on the design code , the differential settlements between embankments and structures have to be controlled less than 10 cm. Post construction settlements of embankments have to be less than 30 cm during the post construction period of 15 years . It is clear that the magnitude and rates of the embankment settlements are the extremely important problem to make the project reliable and economical .

3. 2 Subsurface conditions

The section A of Lianxu highway passes over the marine deposit plain. The typical subsoil profile consists of 0 to 3m think upper crust of stiff clay underlain by a 5.6 to 13m thick soft clay ,which is named Jiangsu Marine clay. Blow this soft clay , lies alternating layers of stiff clay and dense sand extending to badrock with the varied thickness of 10 to 20m.

3. 3 Soil improvement and embankment construction

Dry Jet Mixing and stage construction with sand blanket have been designed to reduce the total settlement and post construction settlement . The embankment filled with residual clay from Dec. 1999. After the first stage construction of 2.5~3.5 m high , about 6 months were left along for soil consolidation. The settlements are observed regularly by settlement plates . During the period of the first stage consolidation , some observational settlements are found to be larger than the corresponding designed total settlement . It is necessary to re-predict the behavior of the embankments based on the settlement observational results of the first stage construction , in order to modify the original design and make the reliable decision for next stage construction.

3. 4 Prediction of the final settlement

The typical fill heights with time and measured ground surface settlements at

the center of embankments with sand blankets are shown. It can be seen that the settlement curve drops significantly between the first stage and second stage construction. The final settlements of the second stage construction are predicted from the first stage observational data by the stage observational method. It indicates that the predicted settlements are basically consistent with the measured settlement . Table 1 also shows the bake analyzed values of undrained elastic modulus E u and coefficient of consolidation C v based on the first stage observational data , giving ranges of E u / c u ratio of 50~100 and C V (field) /C V (lab) ratio of 6~12. It seems to be in the lower range of the E u / c u ratio for Jiangsu Marine clay compared with the ratio of 70~253 for Bangkok clay and other clays existing in the different literature. The actual coefficient of consolidation appears one order of magnitude larger than the laboratory value , this resulting in the faster rate of measured settlement .

4. Conclusions

On the basis of theoretical derivation of Asaoka method and case study of Jiangsu Marine clay , this paper presented a Stage Observational Method for settlement prediction of embankments on soft ground with stage construction. The following conclusions can be given:

(1) Considering the available observational methods for ultimate settlement prediction , the Asaoka method may be successfully extended to make the settlement prediction for stage construction embankments .

(2) The immediate settlement S e is verified to be equal to the intercept

βin

the S j and S j-1 space of the Asaoka method , therefore , the undrained modulus of soft ground can be obtained from the first stage construction measurements , this contributing to the more accurate estimation of immediate settlement of the next stage construction.

(3) Assuming the actual coefficient of consolidation and the thickness of the soft ground remain constant during stage construction , the shifting distances of the parallel lines with the slope of

βis equaled to the immediate settlements , which

1

can be calculated with the inverse modulus from the first (last) stage construction.

(4) The distinct advantage of the recommended method is that the values of undrained modulus and coefficient of consolidation for next stage construction are inversely analyzed from the first (last) stage construction.

(5) From the case study , the value of E u / c u ratio ranges from 50 to 100 for Jiangsu Marine clay , while the actual coefficient of consolidation is almost one order of magnitude larger than the laboratory data.

Acknowledgement

The research is sponsored by Doctoral Program Funds of Education Ministry of China. The support is grateful acknowledged.

软土地基上分期施工的路堤沉降预测方法

摘要:沉降量和沉降速率控制是软土地基上路堤工程设计的关键问题,由于固结理论的局限性和参数的不确定性,理论预测的精度较低,而基于现场实测数据的观测法则显示出了较高的精度。本文在Asaoka观测法的基础上,形成了一种软土路基上分期施工时路堤沉降预测的方法,结合江苏海相软土上的高速公路工程进行了沉降预测分析。

关键词:沉降, 路堤, 观测法, 分期施工

1. 简介

对于软土地基上的路堤设计来说,沉降和稳定性是需要考虑的两个关键性因素。现有的评估路堤稳定性的方法基本上能满足设计要求。因此,沉降便成了设计分析路堤长久性的关键参数。换句话说,对沉降的分析是路堤分析的最合适的方法。

软土地基上路堤的沉降主要是由于路堤的固结和侧向流动所引起的。对于软土地基上的路堤,人们做了很多这方面的研究。

很多实验已经得出了对于预估沉降量和沉降率的实际值的理论,同时,实验也解释了一些涉及精确预估沉降量的问题。Duncan于1993年、Olson于1998年分别对预估沉降量在现有条件下所引起缺陷的不确定性因素进行了分析。这些不确定性因素使得估算路堤沉降量和沉降速率有时特别困难甚至是无法进行估算。尽管数值分析法能提高计算的精确性,但是土的本构模型涉及到很多不能被确定的参数。然而,随着数值分析法的计算化,这使得我们可以获得更多的土的本构模型和相应的程序代码,从而使计算得以简化得以更精确。

因此,人们非常渴望发展这样一种观测方法——只要记录足够的沉降参数,通过计算机就能得到精确的沉降值。很多研究人员在现场观测的基础上发展了沉降预估法。该方法不仅能够得到精确解,还被认可为估算最终沉降量和沉降速率的方法。

分期施工对于软土地基上的路堤来说是一个特殊的程序。随着每一个施工期路堤的固结,路堤的安全性会逐渐提高,竣工后的沉降量也会减少。施工时期的沉降—时间(s-t)曲线可能会比瞬时荷载的曲线更为复杂。尽管竣工后的沉降量会减少,但是施工时期路堤在稳定的最终荷载作用下的初始的固结期会明显增加。为了加快沉降速率,减小软土层的竣工后的二次沉降,实际中我们经常采用超载,也就是在竣工时期加临时荷载,然后卸载。

对于软土层上路堤的施工期的沉降分析的问题有如下几种:

(1)预估施工时期由于钻孔测试而引起的变形。

(2)预估在永久荷载作用下由于第一施工期所引起的最终沉降。

(3)预估在永久荷载和相应的超载下由于超载所引起的竣工后的沉降。

第一个问题主要依赖于设计时的理论。其余两个问题需要以经验为根据而不是靠理论

方法。因为它们是靠观测的数据而得来的。在任何情况下,第二个和第三个从现场观测到的预估沉降量比理论算得的沉降量都可靠。

Leroueil et al 提出了有效应力路径,分析了施工时期竖向沉降和横向沉降之间的关系。Stamatopoulos 和Kotzias 发展了在永久荷载下确定最终沉降的方法,但这种方法是基于弹性理论的,而且它很难用来计算沉降率。而双曲线模型的方法又是依据总的荷载—沉降关系来预估最终沉降量,这种方法对于在初始天然荷载下的沉降很不灵敏。

本文在Asaoka 观测法的基础上,提出了一种软土地基上分期施工时在永久荷载作用下的预估最终沉降的方法。

2. 分期观测法

Asaoka 建议采取一个“观测过程”,利用现场观测的数据来估算最终沉降量和原位固结系数。这种方法因为其简单性和有效性而变得越来越受欢迎。

该方法是基于单向固结沉降量S0 , S1 , S2 , …… ,Sj 在时间0 ,?t ,2?t ,…… ,

j ?t 时能被作为第一近似值,公式如下:

S j =0β+1βS j-1 (2-1)

在时间Sj- Sj-1图里它代表了一条直线。这里0β是直线的截距,1β是直线的倾角。当达到最终沉降时:Sj= Sj-1=Sf ,因此,最终沉降Sf 可以由如下公式求得:

S f =10

1ββ- (2-2)

ln 1β= - 26H t

C V ?(两面排水时) (2-3)

ln 1β= - 22H t

C V ?(顶部排水时) (2-4)

常数1β和固结系数C V 有关:Magnan 和Deroy 认为

对于横向排水:

C h =

t F D e ??-12ln 8β (2-5) 对于竖向排水:

C v =t H ??-12ln 12

5β (2-6) 这里De ,H 分别是排水路径的长度。

Asaoka 观测法也表明,Sj- Sj-1图中的直线在多级荷载作用下会改变位置,而且,当沉降相对较小而粘土层相对较厚时,移动的直线基本上和初始直线是平行的。但是,该

方法并没有讨论给出如何确定从一个直线段到下一个直线段的移动距离。

在表达式(1)中,当j = 0时,t = 0,S(t=0) = S0 ,这里t 是荷载的工作时间。如果在荷载卸载的瞬间将t 设置为0,那么Sj-1就变为0。因此

S 0 = 0β=瞬时沉降S e (2-7)

这就意味着Asaoka 观测法能被扩展为求固结沉降,其值等于S j - S j-1图里的 直线的截

距0β,这里t = 0是在荷载加上之后。此外,这种瞬时沉降也是分期施工期平行线的移动距离。

事实上,根据Asaoka 观测法的最初土层的沉降值能由下式求得:

S t = dz z t H ?0),(ε (2-8)

+'++++'++=)(51)(31)(41)(21),(243242F C Z F C Z ZF T C Z T C Z T z t V V V V !!!!ε (2-9)

这里T 和F 是两个未知的时间系数。

在竖向排水的底部和土层的顶部,),(z t ε=T=ε(t , z=0) 。如果t = 0,那么),(z t ε=ε(t=0 , z=0) =e ε=初始弹性应变。因此,S(t=0)=S 0就能得到瞬时沉降S e 。S e 也能由如下弹性原理的

公式求解:

S 0=S e =u E qbI

V )1(2- (2-10) 上式清楚地表明Asaoka 观测法能够被扩展到估算施工期路堤的沉降。也就是说,下一个施工期的路堤的状况可由上一个施工期的0β,1β进行估算。上一个施工期的路堤的沉降测量值越多,下一个施工期的估算值就越精确。分期观测法包括以下几个步骤:

(1)观察时间—沉降曲线的草图

(2)选择时间间隔?t ,通常是10到100天之间。在t j 时刻读取曲线上的沉降S j 。

(3)在相应的坐标系里以S j - S j-1为轴,从0开始标出沉降S j - S j-1的点。

(4)用直线将标出的点连起来,直线相应的倾角是1β,在S j 轴上的截距为0β,与45o 直线的交点是第一工期的最后固结沉降量。

(5)利用第一工期的0β通过(2-10)式反求不排水压缩模量。

(6)通过已知的E u 来确定下一工期的路堤沉降,从而确定直线段的移动距离。

(7)假设C V 在分期施工时是连续的,并且假设相对于软土的厚度来说路堤沉降非常小,

这可以保证下一工期的直线段平行于第一施工期的直线段。

(8)从与45o斜线的交点预估下一施工期的最后沉降量。

(9)利用1 的值通过式(2-5)、(2-6)分别估算C h和C V。

3. 实例研究

3.1 工程地址和工程概述

连云港—徐州高速公路的A段是一段长31km的高速公路,它把港口城市连云港和国家高速公路网连在一起。该工程于1999年12月开始动工。这其中包括104座桥和涵洞。该高速公路路堤的底部宽40m,高从3m到7m不等。

根据设计标准,路堤和结构的沉降值必须控制在10cm以内。竣工后的路堤沉降在建成后的15年里必须小于30cm。很明显,路堤的沉降量和沉降速率对工程的可靠性和经济性是至关重要的。

3.2 地面下的土质条件

连徐高速公路的A段要经过海相沉积平原。该平原的地基土剖面图包括0到3m厚的上层硬表层的硬粘土,其下是5.6m到13m厚的软粘土,别名江苏海相软土。软粘土下是交替间隔的硬粘土和稠粘土,厚度从10m到20m,它们一直延伸到基岩。

3.3 土层的改良和路堤的施工

我们设计采用干射搅拌法和砂垫层分期施工法来减少总的沉降和竣工后的沉降。从1999年12月开始,路堤用残积粘土填充,在第一期施工到2.5—3.5m高后,让土自然固结6个月。固结沉降期间通过沉降板定期观测路堤的沉降,这一期间,一些观测到的沉降比相应的设计总沉降还大。为了修改原先的设计,使得下一施工期的方案更可靠,我们有必要再次预估基于第一施工期沉降观测结果的路堤的性状。

3.4 预估最终沉降

从路堤填充高度和对路堤中心处砂垫层的地表沉降测试结果中,我们发现第一期和第二期的沉降曲线下降非常陡。第二施工期后的最后沉降可以由分期观测法通过第一期的观测数据来预测。这表明预估沉降量和测试沉降量基本上是相符的。曲线同时也表明基于第一期观测数据的不排水弹性模量Eu和CV的有效性。Eu/cu的比率为50—100,而CV(现场)/CV(室内)的比率为6—12。这也似乎表明江苏海相粘土Eu/cu在低范围内的比率符合。Bangkok粘土和其它已经存在的粘土的比率为70—253(也就是计算数据是有效的),而实际的固结系数值大于试验测得的值,这会导致更快速率的沉降。

4. 结论

基于Asaoka观测法的理论来源,结合对江苏海相粘土的研究,本文发展了一种软土路基上分期施工时路堤沉降预测的方法。结论如下:

(1)对比所有的最终沉降预测的观测方法,Asaoka观测法能够成功地扩展到预测分期

施工路堤的沉降。

β

(2)在根据Asaoka观测法绘制的Sj-和Sj-1图中,瞬时沉降Se被证明是等于截距0的。因此,在第一期观测中,我们能够得到软土层的不排水压缩模量。它有助于我们更精确地估算下一期的瞬时沉降。

(3)假定实际的固结系数和土层厚度在分期施工期仍然保持连续,倾角1β的平行线段的移动距离等于第一分期由公式反求的瞬时沉降值。

(4)本文所介绍的这种方法的优点是下一个分期的不排水压缩模量的值和固结系数的值可由第一分期的计算分析获得。

(5)实例研究表明,江苏海相软土的Eu/cu的比率从50到100不等,而实际的固结系数几乎都比实验室试验所得的数据大。

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开挖工程支撑体系的发展 1.引言 几乎所有土木工程建设项目(如建筑物,道路,隧道,桥梁,污水处理厂,管道,下水道)都涉及泥土挖掘的一些工程量。往往由于由相邻的结构,特性线,或使用权空间的限制,必须要一个土地固定系统,以允许土壤被挖掘到所需的深度。历史上,许多挖掘支撑系统已经开发出来。其中,现在比较常见的几种方法是:板桩,钻孔桩墙,泥浆墙。 土地固定系统的选择是由技术性能要求和施工可行性(例如手段,方法)决定的,包括执行的可靠性,而成本考虑了这些之后,其他问题也得到解决。通常环境后果(用于处理废泥浆和钻井液如监管要求)也非常被关注(邱阳、1998)。 土地固定系统通常是建设项目的较大的一个组成部分。如果不能按时完成项目,将极大地影响总成本。通常首先建造支撑,在许多情况下,临时支撑系统是用于支持在挖掘以允许进行不断施工,直到永久系统被构造。临时系统可以被去除或留在原处。 打桩时,因撞击或振动它们可能会被赶入到位。在一般情况下,振动是最昂贵的方法,但只适合于松散颗粒材料,土壤中具有较高电阻(例如,通过鹅卵石)的不能使用。采用打入桩系统通常是中间的成本和适合于软沉积物(包括粘性和非粘性),只要该矿床是免费的鹅卵石或更大的岩石。 通常,垂直元素(例如桩)的前安装挖掘工程和水平元件(如内部支撑或绑回)被安装为挖掘工程的进行下去,从而限制了跨距长度,以便减少在垂直开发弯矩元素。在填充情况下,桩可先设置,从在斜坡的底部其嵌入悬挑起来,安装作为填充进步水平元素(如搭背或土钉)。如果滞后是用来保持垂直元素之间的土壤中,它被安装为挖掘工程的进行下去,或之前以填补位置。 吉尔- 马丁等人(2010)提供了一个数值计算程序,以获取圆形桩承受轴向载荷和统一标志(如悬臂桩)的单轴弯矩的最佳纵筋。他们开发的两种优化流程:用一个或两个直径为纵向钢筋。优化增强模式允许大量减少的设计要求钢筋的用量,这些减少纵向钢筋可达到50%相对传统的,均匀分布的加固方案。 加固桩集中纵向钢筋最佳的位置在受拉区。除了节约钢筋,所述非对称加强钢筋图案提高抗弯刚度,通过增加转动惯量的转化部分的时刻。这种增加的刚性可能会在一段时间内增加的变形与蠕变相关的费用。评估相对于传统的非对称加强桩的优点,对称,钢筋桩被服务的条件下全面测试来完成的,这种试验是为了验证结构的可行性和取得的变形的原位测量。 基于现场试验中,用于优化的加强图案的优点浇铸钻出孔(CIDH)在巴塞罗那的

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( 二 〇 一 二 年 六 月 外文文献及翻译 题 目: About Buiding on the Structure Design 学生姓名: 学 院:土木工程学院 系 别:建筑工程系 专 业:土木工程(建筑工程方向) 班 级:土木08-4班 指导教师:

英文原文: Building construction concrete crack of prevention and processing Abstract The crack problem of concrete is a widespread existence but again difficult in solve of engineering actual problem, this text carried on a study analysis to a little bit familiar crack problem in the concrete engineering, and aim at concrete the circumstance put forward some prevention, processing measure. Keyword:Concrete crack prevention processing Foreword Concrete's ising 1 kind is anticipate by the freestone bone, cement, water and other mixture but formation of the in addition material of quality brittleness not and all material.Because the concrete construction transform with oneself, control etc. a series problem, harden model of in the concrete existence numerous tiny hole, spirit cave and tiny crack, is exactly because these beginning start blemish of existence just make the concrete present one some not and all the characteristic of quality.The tiny crack is a kind of harmless crack and accept concrete heavy, defend Shen and a little bit other use function not a creation to endanger.But after the concrete be subjected to lotus carry, difference in temperature etc. function, tiny crack would continuously of expand with connect, end formation we can see without the

软土地基处理方案

一、引言 如果地基的承载能力足够,则基础的分布方式可与竖向结构的分布方式相同。但有时由于土或荷载的条件,需要采用满铺的伐形基础。伐形基础有扩大地基接触面的优点,但与独立基础相比,它的造价通常要高的多,因此只在必要时才使用。不论哪一种情况,基础的概念都是把集中荷载分散到地基上,使荷载不超过地基的长期承载力。因此,分散的程度与地基的承载能力成反比。有时,柱子可以直接支承在下面的方形基础上,墙则支承在沿墙长度方向布置的条形基础上。当建筑物只有几层高时,只需要把墙下的条形基础和柱下的方形基础结合使用,就常常足以把荷载传给地基。这些单独基础可用基础梁连接起来,以加强基础抵抗地震的能力。只是在地基非常软弱,或者建筑物比较高的情况下,才需要采用伐形基础。多数建筑物的竖向结构,墙、柱都可以用各自的基础分别支承在地基上。中等地基条件可以要求增设拱式或预应力梁式的基础连接构件,这样可以比独立基础更均匀地分布荷载。 如果地基承载力不足,就可以判定为软弱地基,就必须采取措施对软弱地基进行处理。软弱地基系指主要由淤泥、淤泥质土、冲填土、杂填土或其他高压缩性土层构成的地基。在建筑地基的局部范围内有高压缩性土层时,应按局部软弱土层考虑。勘察时,应查明软弱土层的均匀性、组成、分布范围和土质情况,根据拟采用的地基处理方法提供相应参数。冲填土尚应了解排水固结条件。杂填土应查明堆积历史,明确自重下稳定性、湿陷性等基本因素。 在初步计算时,最好先计算房屋结构的大致重量,并假设它均匀的分布在全部面积上,从而等到平均的荷载值,可以和地基本身的承载力相比较。如果地基的容许承载力大于4 倍的平均荷载值,则用单独基础可能比伐形基础更经济;如果地基的容许承载力小于2倍的平均荷载值,那么建造满铺在全部面积上的伐形基础可能更经济。如果介于二者之间,则用桩基或沉井基础。 二、地基的处理方法 利用软弱土层作为持力层时,可按下列规定执行: 1)淤泥和淤泥质土,宜利用其上覆较好土层作为持力层,当上覆土层较薄,应采取避免施工时对淤泥和淤泥质土扰动的措施; 2)冲填土、建筑垃圾和性能稳定的工业废料,当均匀性和密实度较好时,均可利用作为持力层; 3)对于有机质含量较多的生活垃圾和对基础有侵蚀性的工业废料等杂填土,未经处理不宜作为持力层。局部软弱土层以及暗塘、暗沟等,可采用基础梁、换土、桩基或其他方法处理。在选择地基处理方法时,应综合考虑场地工程地质和水文地质条件、建筑物对地基要求、建筑结构类型和基础型式、周围环境条件、材料供应情况、施工条件等因素,经过技术经济指标比较分析后择优采用。

土木工程外文翻译参考3篇

学校 毕业设计(论文)附件 外文文献翻译 学号: xxxxx 姓名: xxx 所在系别: xxxxx 专业班级: xxx 指导教师: xxxx 原文标题: Building construction concrete crack of prevention and processing 2012年月日 .

建筑施工混凝土裂缝的预防与处理1 摘要 混凝土的裂缝问题是一个普遍存在而又难于解决的工程实际问题,本文对混凝土工程中常见的一些裂缝问题进行了探讨分析,并针对具体情况提出了一些预防、处理措施。 关键词:混凝土裂缝预防处理 前言 混凝土是一种由砂石骨料、水泥、水及其他外加材料混合而形成的非均质脆性材料。由于混凝土施工和本身变形、约束等一系列问题,硬化成型的混凝土中存在着众多的微孔隙、气穴和微裂缝,正是由于这些初始缺陷的存在才使混凝土呈现出一些非均质的特性。微裂缝通常是一种无害裂缝,对混凝土的承重、防渗及其他一些使用功能不产生危害。但是在混凝土受到荷载、温差等作用之后,微裂缝就会不断的扩展和连通,最终形成我们肉眼可见的宏观裂缝,也就是混凝土工程中常说的裂缝。 混凝土建筑和构件通常都是带缝工作的,由于裂缝的存在和发展通常会使内部的钢筋等材料产生腐蚀,降低钢筋混凝土材料的承载能力、耐久性及抗渗能力,影响建筑物的外观、使用寿命,严重者将会威胁到人们的生命和财产安全。很多工程的失事都是由于裂缝的不稳定发展所致。近代科学研究和大量的混凝土工程实践证明,在混凝土工程中裂缝问题是不可避免的,在一定的范围内也是可以接受的,只是要采取有效的措施将其危害程度控制在一定的范围之内。钢筋混凝土规范也明确规定:有些结构在所处的不同条件下,允许存在一定宽度的裂缝。但在施工中应尽量采取有效措施控制裂缝产生,使结构尽可能不出现裂缝或尽量减少裂缝的数量和宽度,尤其要尽量避免有害裂缝的出现,从而确保工程质量。 混凝土裂缝产生的原因很多,有变形引起的裂缝:如温度变化、收缩、膨胀、不均匀沉陷等原因引起的裂缝;有外载作用引起的裂缝;有养护环境不当和化学作用引起的裂缝等等。在实际工程中要区别对待,根据实际情况解决问题。 混凝土工程中常见裂缝及预防: 1.干缩裂缝及预防 干缩裂缝多出现在混凝土养护结束后的一段时间或是混凝土浇筑完毕后的一周左右。水泥浆中水分的蒸发会产生干缩,且这种收缩是不可逆的。干缩裂缝的产生主要是由于混凝土内外水分蒸发程度不同而导致变形不同的结果:混凝土受外部条件的影响,表面水分损失过快,变形较大,内部湿度变化较小变形较小,较大的表面干缩变形受到混凝土内部约束,产生较大拉应力而产生裂缝。相对湿度越低,水泥浆体干缩越大,干缩裂缝越易产 1原文出处及作者:《加拿大土木工程学报》

土木工程毕业设计外文翻译最终中英文

7 Rigid-Frame Structures A rigid-frame high-rise structure typically comprises parallel or orthogonally arranged bents consisting of columns and girders with moment resistant joints. Resistance to horizontal loading is provided by the bending resistance of the columns, girders, and joints. The continuity of the frame also contributes to resisting gravity loading, by reducing the moments in the girders. The advantages of a rigid frame are the simplicity and convenience of its rectangular form.Its unobstructed arrangement, clear of bracing members and structural walls, allows freedom internally for the layout and externally for the fenestration. Rig id frames are considered economical for buildings of up to' about 25 stories, above which their drift resistance is costly to control. If, however, a rigid frame is combined with shear walls or cores, the resulting structure is very much stiffer so that its height potential may extend up to 50 stories or more. A flat plate structure is very similar to a rigid frame, but with slabs replacing the girders As with a rigid frame, horizontal and vertical loadings are resisted in a flat plate structure by the flexural continuity between the vertical and horizontal components. As highly redundant structures, rigid frames are designed initially on the basis of approximate analyses, after which more rigorous analyses and checks can be made. The procedure may typically inc lude the following stages: 1. Estimation of gravity load forces in girders and columns by approximate method. 2. Preliminary estimate of member sizes based on gravity load forces with arbitrary increase in sizes to allow for horizontal loading. 3. Approximate allocation of horizontal loading to bents and preliminary analysis of member forces in bents. 4. Check on drift and adjustment of member sizes if necessary. 5. Check on strength of members for worst combination of gravity and horizontal loading, and adjustment of member sizes if necessary. 6. Computer analysis of total structure for more accurate check on member strengths and drift, with further adjustment of sizes where required. This stage may include the second-order P-Delta effects of gravity loading on the member forces and drift.. 7. Detailed design of members and connections.

软土地基工程中存在的问题及处理方法概要

浅析软土地基工程中存在的问题及处理方法 摘要:软土在荷载作用下,极易产生工程问题,在勘察过程中切不可马虎松懈,本文从软土特性出发,分析了软土工程地基中存在的问题及处理措施,并作出了勘察方法探讨。 关键词:软土地基工程问题勘察方法 中图分类号:tu4文献标识码:a 文章编号: 在公路铁路的修建施工过程中,经常会遇到物理力学性质差且分布面积较大的第四系软土类区域,软土体是自然界的历史产物,它有独特的地域特征,地基条件差别巨大,根据相邻建筑物或相邻地域的地质资料来设计,一点微小的差异就可能给影响工程质量,给工程造成巨大的经济损失,所以应引起重视,我们施工中充分利用信息,及时调整设计参数和工艺,避免了施工期间可能引起的附加沉降,体现了当今勘察设计施工监测为一体的全过程综合岩土工程实践理念。 一、软土的特征及其危害性 软土指的是所含水量大于液限天然孔隙比大于或等于1.0的细粒土,处于软朔或流朔状态。我国的软土主要分布在东南沿海及各大江大河的入海三角洲冲击平原地区。内陆主要是湖泊或山谷冲击而成,有机质含量较高,分布范围比较小。主要包含饱和软粘土包括泥炭、泥炭质土,淤泥、淤泥质土等,软土一般具触变性、流变性、高压缩性、低强度、低透水性、不均匀性等特征,在工程应用上的

表现为地基沉降量大,可以达到数十厘米甚至到数百厘米;地基沉降时间长,达数十年甚至到数百年,特别严重的是沿海地带的软土地基,因为厚度过大,所以固结速度比较慢;地基不均匀沉降,大多是由上部结构的特性和荷载差异所引起;地基抗剪强度低。软土上述的特点,容易影响公路铁路工程质量,引发一些地质灾害,其危害性主要表现为:软土地基不均匀和过大沉降将严重影响路面的平整度,牵制了道路通行能力和安全度;路基路堤还可能会随着软土地基一起产生滑动现象,从而导致路面的整体遭到破坏,鉴于软土地基潜在的种种危害性,各部对于软基的处理标准要求高,也更高地要求了地质勘察在软土地基工程的深度和广度。 二、软土地基工程中存在的问题 由上所述出的软土地基固有的特性以及工程在勘察、设计、施工、管理使用各程序阶段的失误,造成了所建造在软土地基上建筑物的结构损伤工程倒塌等一系列工程事故,大致可分为以下几种情况: (一在地质勘测时深度不够,没有查清楚软土土层的分布、厚度以及一些暗沟暗塘的具体情况,造成建筑物产生严重不均匀沉降,结构构件开裂,甚至工程不负荷载倒塌的事故。 (二由于地质勘察不深入,不细致,未取得的地质资料不具可靠性,以致错误的将软土判断为好的地基土,使设计也随之错误,产生的不均匀沉降使建造物受力结构变化,裂缝倒塌,引起工程事故。 (三软土的承载力比较低,地基无法承受,发生剪切的破坏,基础失去稳定性,带来较大沉降和不均匀沉降,使上部建造物结构受损,造成工程事故。 (四对软土地基未作出处理,或者处理方法不正确,施工质量不过关,使建筑物产生过大的沉降和不均匀沉降,开裂,不得不二次或多次进行加固和处理。 四、软土地基处理措施

土木工程外文翻译5

PROJECTCOSTCONTROL INTRODUCTION project a corporate image window and effectiveness of the source. With increasingly fierce market competition, the quality of work and the construction of civilizations rising material prices fluctuations. uncertainties and other factors, make the project operational in a relatively tough environment. So the cost of control is through the building of the project since the bidding phase of acceptance until the completion of the entire process, It is a comprehensive enterprise cost management an important part, we must organize and control measures in height to the attention with a view to improving the economic efficiency of enterprises to achieve the purpose. 2, outlining the construction project cost control, the cost of the project refers to the cost and process of formation occurred, on the production and operation of the amount of human resources, material resources and expenses, guidance, supervision, regulation and restrictions, in a timely manner to prevent, detect and correct errors in order to control costs in all project costs within the intended target. to guarantee the production and operation of enterprises benefits. 4, the construction cost control measures cost control measures. Reduce the cost of construction projects means, we should not only increase revenue is also reducing expenditure, or both also increase savings. Cutting expenditure is not only revenue, or revenue not only to cut expenditure, it is impossible to achieve the aim of reducing costs, at least there is no ideal lower cost effective.

土木工程毕业设计中英文翻译

附录:中英文翻译 英文部分: LOADS Loads that act on structures are usually classified as dead loads or live loads are fixed in location and constant in magnitude throughout the life of the the self-weight of a structure is the most important part of the structure and the unit weight of the density varies from about 90 to 120 pcf (14 to 19 KN/m)for lightweight concrete,and is about 145 pcf (23 KN/m)for normal calculating the dead load of structural concrete,usually a 5 pcf (1 KN/m)increment is included with the weight of the concrete to account for the presence of the reinforcement. Live loads are loads such as occupancy,snow,wind,or traffic loads,or seismic may be either fully or partially in place,or not present at may also change in location. Althought it is the responsibility of the engineer to calculate dead loads,live loads are usually specified by local,regional,or national codes and sources are the publications of the American National Standards Institute,the American Association of State Highway and Transportation Officials and,for wind loads,the recommendations of the ASCE Task Committee on Wind Forces. Specified live the loads usually include some allowance for overload,and may include measures such as posting of maximum loads will not be is oftern important to distinguish between the

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