电大岩土力学试题3答案小抄

1、一、填空题（本大题共5小题，每空3分，总计30分，卷中水的密度均为1g/cm3）1、在粒度分析累计曲线法中，小于某粒径土的百分含量与土粒粒径的关系为，则该土的曲率系数为1.5，不均匀系数为6，土体级配不好（填好、不好、一般）。2、试验土样体积60cm3，质量300g，烘干后质量为260g，则该土样的干密度为4.35g/ cm3。3、试验土样自然状态质量为300g，恰好成为塑态时质量为260 g，恰好成为液态时质量为340 g，则该土样的液性指数为0.5，自然状态下土体处于可塑状态。4、蒸馏水在某试验土样中的渗流速度为0.1m/s，该土样的渗透系数为510-8 m/s，则当水在土样中流动时产生的

2、动水力为21010 n/m3。5、某矩形基础底面长2m，宽1m，自重5kn，上部载荷20kn，当载荷轴线与矩形中心重合时，基底压力为12.5kn/m2；当载荷轴线偏心距为基础宽度1/12时，基底最大压力为18.75kn/m2，基底最小压力为6.25kn/m2二、 计算题（本大题共2小题，总计30分）6、某饱和土样质量为200g，体积为60cm3，含水量为40%，孔隙比为0.5，试求该土样的饱和密度？（10分）解： （3分） cm3 （3分） g/ cm3 （1分） g/ cm3 （3分）7、某重力式挡土墙墙高6m，墙背直立光滑。水位自墙脚算起高为=5m，现拟用=19kn/m3, =25.9kn

3、/m3,摩擦角=300，含水量=18%的细砂作为填料，（1）当填土至水位高度时（填土表面水平），墙后填土处于弹性平衡状态，且此时填土的泊松比为0.25，试求此时作用在每延米挡土墙上的静止土压力？（10分）（2）当填土至与墙等高时（填土表面水平），墙后填土处于极限平衡状态，其竖向应力为最小主应力，水平应力为最大主应力，试根据朗金土压力理论计算此时作用在挡土墙上的被动土压力？（10分）解：(1)=（）/(1+) =10kn/m3 （3分）=0.333 （3分） =42kn/m （4分）(2)=3 （1分）水位以上 =28.5kn/m （4分）水位以下 = 660kn/m （4分）所以 =688.5

4、 kn/m （1分）三、 问答题（本大题共4小题，总计40分）8、基坑开挖采用表面直接排水和路堤两侧有水位差时，可能出现怎样的工程危害，试根据所学土力学知识说明危害成因及处理方法？（10分）答：（1）基坑开挖采用表面直接排水可能发生流沙现象（2分）；原因是动水力方向与土体重力方向相反，当土颗粒间的压力等于0时，处于悬浮状态而失稳，则产生流沙现象（2分）；处理方法为采用人工降低地下水位的方法进行施工（1分）。（2）路堤两侧有水位差时可能产生管涌现象（2分）；原因是水在砂性土中渗流时，土中的一些细小颗粒在动水力作用下被水流带走（2分）；处理方法为在路基下游边坡的水下部分设置反滤层（1分）。9、前些

5、年修建在东北地区地下水位较浅路段的公路，目前许多都出现了下述现象：路面松软、开裂、冒泥（翻浆）。试根据所学土力学知识说明现象成因及影响因素？（10分）答：成因主要来源于季节性冻土的冻融（1分），影响因素如下（1）土的因素：土粒较细，亲水性强，毛细作用明显，水上升高度大、速度快，水分迁移阻力小，土体含水量增大，导致强度降低，路面松软、冒泥（3分）；（2）水的因素：地下水位浅，水分补给充足，所以冻害严重，导致路面开裂（3分）；（3）温度的因素。冬季温度降低，土体冻胀，导致路面鼓包、开裂。春季温度升高，土体又会发生融沉（3分）。10、在计算桥墩基础下的地基附加应力中，地基荷载是否为基底压力？请说明原

6、因？（10分）答：不是（1分）。（1）由于桥墩基础埋置较深，基础底面荷载是作用在地基内部某深度处（3分）；（2）因此计算附加应力时应去除基础所占空间处原有土体自重的影响，即计算桥墩基础下的地基附加应力时应用p0计算（3分）；（3）p0=p-d（p-基底压力，-土体重度，d-基础埋深）（3分）。11、砂性土土坡、粘性土土坡的坡高是否受限制？请说明原因？（10分）答： （1）砂性土土坡的坡高不受限制（2分）；根据土坡稳定性分析理论，砂性土的安全系数为：k=tan/tan,所以只要坡角不超过其内摩擦角即可，与坡高无关（3分）。（2）粘性土土坡的坡高受限制（2分）；根据土坡稳定性分析理论，砂性土的安全

7、系数为：k=动力矩/阻力矩，而土坡高度的变化对动力矩和阻力矩均会产生影响，进而导致圆弧滑动面产生的位置发生变化，因此粘性土土坡的坡高受限制（3分）。winger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final win over england, has been passed fit after a lower-leg injury, while slater has been named at full-back but is still recovering from a knee injury aggra

8、vated against usa.both sides boast 100% records heading into the encounter but australia have not conceded a try since josh charnleys effort in their first pool match against england on the opening day.aussie winger jarryd hayne is the competitions top try scorer with nine, closely followed by tuiva

9、sa-sheck with eight.but it is recently named rugby league international federation player of the year sonny bill williams who has attracted the most interest in the tournament so far.the kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the world cup in b

10、oth rugby league and rugby union after triumphing with the all blacks in 2011.id give every award back in a heartbeat just to get across the line this weekend, said williams.the (lack of) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the foo

11、tball associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomorrow and i have asked to meet yaya toure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his exp

12、erience was.uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of european footballs governing body, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappoin

13、ted by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska. baumgartner the disappointing news: mission aborted.the supersonic descent could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditi

14、ons have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everes

15、t (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space a

16、t 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.they blew it in 2008 when they got caught cold in the final and they will not make the same mistake against the kiwis in manchester.five years ago they cruised through to the final and

17、 so far history has repeated itself here - the last try they conceded was scored by englands josh charnley in the opening game of the tournament.that could be classed as a weakness, a team under-cooked - but i have been impressed by the kangaroos focus in their games since then.they have been concen

18、trating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line, completing sets and a good kick-chase. theyve been great at all the unglamorous stuff that often goes unnoticed in the stands but not by your team-mates.it is as though their entire tournament has been preparation for the final.in johnathan thurston, cooper cronk, cameron smith and either billy slater or greg inglis at full-back they have a spine that is unmatched in rugby league. they have played in so many high-pressure games - a priceless as