1、桩的排列形式采用行列式，基桩布置如图1所示:00XI三、拟定桩长并验算单桩轴向受压容许承载力 承台每延米自重：A0=l 1.88x16.38x（25-19.8） =1011. 89kN/m土层I中桩每延米自重：a=-xl.82x（25-l 9.8） = 13.232kN / m土层II中桩每延米自重：q2 =lxl.82x（25-21.8） = 8.143kN/m设：第二层土中桩长为伽根据要求，一般应将桩底至于岩层或坚硬的土层中，已得到较大的承载 力和较小的沉降量，若在施工条件允许的深度内没有坚硬土层的存在, 应尽可能选择压缩性较低、强度较高的土层作为持力层，要避免是桩底 坐落在软土层上或离软
2、弱下卧层的距离太近，以免桩基础发生过大的沉 降。显然，土层H相对于土层I更适合成为持力层。桩底所承受的最大竖向荷载最大值为：=（A；_/12 + 1x3.5/12 + 12.5xl3.232+/?ux8.143）= 74958/12 + 1011.89x3.5/12 +13.232xl2.5 + 8.143x/?u= 6707.03 + x8.143计算出时取以下数据：_ .c e A. = 7rd2 =-xxl.82 = 2.54m桩的周长 = /rd = /rxL8=565m 1 4 42 = 0.85,/h0 =0&心=6 o = 5OOkpa /2 =（16x19.8 + /% x21
3、.8）/（16 + /?u） 所以承载力：7?a = O.5x 5.65 x （55 xl2.5 + 70x /?u） + 2.54 x（0.8x0.85x（500+6x（16xl9-8+21-8x/?U）x（13n）（16+知） U=6707.83+ 8.143 x/?解之的伽=2 m 取伽=35m因此拟定桩长为：=12.5 + 3.5 = 16m桩端以上各土层的加权平均重度值为:16x19.8 + 3.5x21.8= 20.16kN/m35/25桩端处土的承载力容许值：= O.8xO.855OO + 6x2 06x（19.5-3）= 1697.2kPa因为乞=1697.2kPa 1450k
4、Pa 所以取 = 1450kPa单桩轴向受压承载力容许值的计算：/ /-I=gx5.65x（55x 12.5 + 70x3.5） + 2.54x1450= 631731kN桩底所承受的最大竖向荷载M =（皿/12 + 13232+伽8143）=6735.53kN因为不满足要求，所以需重新拟定桩长。2x6735.53-2.54x1450565-55x12.5 /70 = 5.6m取知=6.5m。验算单桩轴向受压容许承载力/2 =16x19.8 + 65x21.816 + 6.5= 20.38kN/m3桩端处土的承载力容许值:4 =叫必 + 哄 5 一 3）= 0.8x0.85 500 + 6x
5、20.38 x （22.5 - 3）= 1961.43kPa因为= 1961.43kPa1450kPa 所以取s = 1450kPa单桩轴向受压承载力容许值的计算:&冷皿+也=-x 5.65x（55x12.5+ 70x6.5）+ 2.54x1450= 6910.56kN心=（N：/12 + Mx3.5/12 + 12.5xl3.232+伽 x&143） =6759.96kN因为血= 1.0m时,故桩的计算宽度为：4 =他（ + 1）平行于水平力作用方向的桩间净距为厶=必-1.8 = 2.7m地面线以下桩的计算埋入深度几=3（ +1） = 3x（1.8 +1） = 8.4m ,且厶=2.7m O
6、.6/1 = 5.04m 旨斤、j式中：b厂-桩的计算宽度（m） ,b】S2d；d-桩径（m）；%-桩形换算系数，本题取k=0.9：优一_与水平外力作用方向的一排桩的桩数“有关的系数，本题取b： =0.5o计算可得：k=b, + =0.5+ x = 0.7679-0.6 h、 0.6 8.4b、=kkf （d +1）=0.7679 x0.9x（ 1.8+1 ）= 1.935mb、= 1.935m 2d = 3.6m,符合要求。hm = 2（ + 1） = 2x（1.8 + 1） = 5.6m m22 5” = 19m = 8.976m桩的入土深度 -2785 ,故按照弹，性桩计算。五、桩顶荷载
7、分配并校核1）桩顶刚度系数Opp、Anp Q踰值的计算:厶=0,力=19m,g =,州= 7rd2 = 2.54m2 2 4CRj = 6910.56kN,不满足要求，所以进行重新计算。/?n= 2 x 7669 6 - 2皿 x 145 一 55 % 12.5 /70 = 10.34m取加= 11.5m。= 20.64 kN/nr16x19.8 + 11.5x21.816 + 11.5乞=叭仇（ +底人（力一 3）= 0.8x0.85 500 + 6x 20.64 x 24.5= 2403.17kPa因为4 = 2403.17kPa1450kPa 所以取乞= 1450kPa=-x5.65x
8、（55x 12.5 + 70x 11.5）+ 2.54 x 1450=7899.3 lkN因为 /Vnux=7669.06kN4,故可以采用无量纲法心和+以=624.4轴+33沁无量纲系数AM,BM分别由附表查的，Mz计算如下表:MZ计算列表Z = azZAwMz0.00.001.00000332.810.10.360.099600.9997462.20332.72394.920.20.720.196960.99806122.99332.16455.160.31.080.290100.99382181.15330.75511.910.41.440.377390.98617235.66328.2
9、1563.870.51.800.457520.97458285.70324.35610.050.62.150.529380.95861330.57319.03649.610.72.510.592280.93817369.85312.23682.080.82.870.645610.91324403.15303.94707.090.93.230.689260.88407430.41294.23724.641.03.590.723050.85089451.51283.18734.691.13.950.747140.81410466.55270.94737.491.24.310.761830.7741
10、5475.72257.64733.371.34.670.767610.73161479.33243.49722.821.45.030.764980.68694477.69228.62706.311.55.390.754660.64081471.25213.27684.521.65.750.737340.59373460.43197.60658.031.76.100.713810.54625445.74181.80627.541.86.460.684880.49889427.67166.04593.711.96.820.651390.45219406.76150.49557.252.07.180
11、.614130.40658383.49135.31518.812.27.900.531600.32025331.96106.58438.542.48.620.443340.24262276.8480.75357.592.69.340.354580.17546221.4258.39279.812.810.050.269960.11979168.5839.87208.443.010.770.193050.07595120.5525.28145.833.512.570.050810.0135431.734.5136.234.014.360.000050.000090.030.062）桩身最大弯矩Mm
12、ax最大弯矩位置确定由QZ=O得：由0=0.533及応4,查附表13,得Z-=L0091,故由=1-0091及 = 4,查书中附表13,得KM= 1.780Mnm= KM = 1.780x332.81 = 592.40kTVm（2）桩身剪力Qz计算Qz = Q）州 + 沁 Bq = 173.91 血 +92.69Bq无量纲系数AQ,BQ分别由附表查的，Qz计算如下表QZ计算列表AqBqQ173.910.98833-0.00753171.88-0.70171.180.95551-0.02795166.17-2.59163.580.90468-0.05820157.33-5.39151.940.8
13、3898-0.09554145.91-8.86137.050.76145-0.13747132.42-12.74119.680.67486-0.18191117.36-16.86100.500.58201-0.22685101.22-21.0380.190.48522-0.2708784.38-25.1159.280.38689-0.3124567.28-28.9638.320.28901-0.3505950.26-32.5017.770.19388-0.3844333.72-35.63-1.920.10153-0.4133517.66-38.31-20.660.01477-0.436902.
14、57-40.50-37.93-0.06586-0.45486-11.45-42.16-53.61-0.13952-0.46715-24.26-43.30-67.56-0.20555-0.47378-35.75-43.91-79.66-0.26359-0.47496-45.84-44.02-89.86-0.31345-0.47103-54.51-43.66-98.17-0.35501-0.46223-61.74-42.84-104.58-0.38839-0.44914-67.54-41.63-109.18-0.43174-0.41179-75.08-38.17-113.25-0.44647-0.
15、36312-77.65-33.66-111.30-0.43651-0.30732-75.91-28.49-104.40-0.40641-0.24853-70.68-23.04-93.72-0.36065-0.19052-62.72-17.66-80.38-0.19975-0.01672-34.74-1.55-36.29-0.00002-0.00045-0.04-0.05（3）水平位移Xz计算* 产嘉人 + 鑰F6.97xg”i+3.72x1。*,无量纲系数Ax,Ex分别由附表查的，Xz计算如下表XZ计算列表BxXz2.440661.6210017.016.0323.042.278731.4509415.885.4021.282.117791.2908814.764.8019.561.958811.1407913.654.2417.901.802731.000643.7216.291.650420.8703611.503.2414.741.502680.7498110.472.7913.261.360240.638859.482.3811.861.223700.537278.532.0010.531.093610.444817.621.659.283.
