地基沉降计算

点为e?1.079,lgpc?2.238,还原为压力pc?173kPa。 表

lgp 1.544 1.024 1.940 0.989 2.238 1.079 2.539 0.952 2.841 0.913 3.142 0.835 3.443 0.725 3.744 0.617 4.045 0.501 e (2)压缩指数Cc

由e?lgp曲线的直线段,当?e?0.11时,?lgp?0.301,则

Cc??e0.11??0.3564 ?lgp0.301(3)粘土层最终压缩量

粘土层厚4m,土层中点处的自重应力为:

p0?18.5?3?(19.8?10)?6?(17.8?10)?2?129.9kPa

因p0?129.9kPa

1?1.060129.91739 [解]

(1)侧压力系数k0??x/?z?50/100?0.5 由 k0??1?????k0?1/3 (?为土的泊松比) 1?k02?2) 又 E0?Es(1?1??代数得: Es?22.5Mpa (2)由 s??p100kpa?H??100mm?0.44mm Es22.5Mpa10 [解]

水位下降前后自重应力分布图(a),水位下降后自重应力增量(b)。

1m18?1?182m18?12?2?4218?20?2?58水位下降后16水位下降前3m42?9?3?69z58?9?3?8516 z

(1)地表面下沉量:根据 S??pH,?p???c?,得 Es s地表?1/2?16?216??3?22.4mm

2.53(2)第?层土因为没有应力变化,故无压缩量

(3)第???层表面沉降量: s???表?11[解] (1)

16?3?16mm 3k(1?e)5?10?8?(1?0.8)?105 cv???0.00225cm2/s?7.1?104cm2/y

a??w0.4?10cvt7.1?140? Tv?2?5002H()2由Uz?1?0.5?0.56 88?2exp(??24Tv)得U?0.8 (或查Uz?Tv曲线得到)

Es?1?e1?0.8??103?4500kpa a0.4土层最终沉降量为 s?p?p150H?0?H??5000?167mm EsEs4500加荷半年后地基沉降量 st?Uz?s?0.8?16?7(2)由Uz?70%,得Tv?0.4

1mm34

cvtTvH20.4?2502由 Tv?2?t???0.35年 4Hcv7.1?1012 [解] (1)Es?1?e11?e11?e11?0.8???p0??p0?120p0 e1?e2e1?e2a0.8?0.785p0最终沉降量为: s?pp0?pH?0?H??500?4.2cm EsEs120p0(2)由Uz?1?8?2exp(??24Tv)(或查Uz?Tv曲线得到)

当Uz?80% Tv?cvt/H2?0.56 7当Uz?60% Tv?0.286

cv?t1cv?t20.567t1H220.56730?500020.567 ??????H12H220.287t2H120.28760?24?365?102?t20.287 t2?7.2(年) 13[解] (1)pk?Fk900??Gd??20?1?122.86kpa A3.5?2.5(2)p0?pk??0d?122.86?18?1?104.86kpa (3)因为7m处为基岩,故zn?7?1?6m (4)Es?1?e11?1.0??5Mpa a0.4(5)沉降量的计算如表3-2

(6)s??ss??54.91?1?54.91mm

z(m)06lb1.751.25?1.4zb0?i0.2500?4?1?izi?izi??i?1zi?1Esips??0?(?izi??i?1zi?1)(mm)(Mpa)Esi50.1091?4?0.43646?0.4364?2.61842.6184?0?2.6184554.91

14 [解]

(1)先期固结压力:

pcA?16.8?3?18?1?68.4kpa pcB?68.4?9.7?7?136.3kpa

pcC?136.3?10?4?176.3kpa开挖后的自重应力:

?cA?18kpa

?cB?18?9.7?7?85.9kpa

?cC?85.9?10?4?125.9kpa68.4?136.3?102.35kpa

218?85.9p1??51.95kpa2120?60?p??90kpa2

pcp1??p?H?s?Clog?Clog?e?c1?e0?p1pc?(2) pc?

?7000102.35141.95?[0.05?log?0.2?log]?176mm1?0.7251.95102.3515.解: 有限厚度弹性土层上作用有柔性荷载时沉降计算可采用:

s?sz?0?sz?H

均布柔性圆形荷载作用下底面沉降计算式为;

pb(1??2)s?I1

E对z?0处:

中心点:r?0 I1?2.000 边缘点:r?4m I1?1.273

s中心200?400?(1?0.352)??2?14.04cm

10?103200?400?(1?0.352)??1.273?8.936cm

10?103ds?ed(1?w)?w?w,e?s?1 1?e?s边缘16.解: ?sat?粉质粘土层:?sat?(1?1.7?19)?10?19.2(kN/m3)

2.7?1.3?101.72?17.8)?10?17.93(kN/m3)

2.72?1.42?10F?G??d?601.8(kN/m) 基底附加压力:p0?p??c?A淤泥质粘土层:?sat?(1?沉降计算见下表格: 分层厚度为1m 点 深度 自重 附加应厚自重应力平自重应力平自重压 应力 力 度 均值 均值 应力缩加附曲zi ?c ?z??z?Hi ?c(i?1)??ci?z(i?1)??zi加应线 22 力 受压受压e1i?e2isi??前孔后孔1?e1i隙比 隙比 103? e1i e2i (m) (kpa)(kpa) (m)(kpa) 0 0 1 0.5 2 1.5 3 2.5 4 3.5 5 4.5 6 5.5 7 6.5 8 7.5 9 8.5 10 9.5 18.2 601.8 (kpa) 589.8 490.5 340 243.7 191 156.5 130 111.4 97.8 87.3 79 72.2 67 61 54.2 48.2 42.1 36.1 e1i?e2iHi1?e1i(mm) 610.2 1 0.756 0.616 0.0797 39.9 517.7 2 0.841 0.709 0.072 72 375.8 3 0.973 0.71 0.133 133 287.4 3 0.956 0.752 0.104 104 242.6 3 0.940 0.774 0.086 86 216.1 3 0.931 0.786 0.075 75 197.5 3 0.922 0.796 0.066 66 186.8 3 0.914 0.806 0.056 56 181.1 3 0.905 0.811 0.049 49 178.6 3 0.896 0.814 0.043 43 178.2 3 0.887 0.814 0.039 39 179.3 3 0.879 0.813 0.035 35 182.1 3 0.872 0.81 0.033 33 184 3 0.865 0.809 0.03 30 185.2 3 0.857 0.808 0.026 26 187.2 3 0.850 0.806 0.024 24 188.9 3 0.843 0.804 0.021 21 190.8 3 0.836 0.802 0.019 19 22.6 577.7 0.5 20.4 31.8 403.2 1 27.2 39.73 276.8 1 35.8 47.66 210.6 1 43.7 55.59 171.5 1 51.6 63.52 141.4 1 59.6 71.45 118.9 1 67.5 79.38 103.8 1 75.4 87.31 91.8 95.24 82.7 1 83.3 1 91.3 1 99.2 1 107.1 1 115.1 1 123 1 131 1 139 1 146.8 1 154.7 11 10.5 103.2 75.2 12 11.5 111.1 69.2 13 12.5 119 64.7 14 13.5 126.9 57.2 15 14.5 134.9 51.2 16 15.5 142.8 45.1 17 16.5 150.7 39.1 18 17.5 158.7 33.1

最终沉降=950.9(mm)

各个土层得压缩曲线:

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