02 1.323[a(?f r??)c - b] =2.15 4.5?)?- 0.041] = 0.548÷ ´ (10 - 20)+ 20 = 15.25KPa由直线内插法得:H=4.8m 时, q = ç则温度疲劳应力:s t = kts tm = 0.548 ´ 2.02 = 1.11MPa综合,二级公路的安全等级为三级,相应于三级的安全等级的变异水平等级为中级,目标可靠度为 85﹪。再根据查得的目标可靠度和变异水平等级,确定可靠度系数g g = 1.13 。g g (s pr + s tr )= 1.13 ´ (2.65 + 1.11) = 4.26MPa < fr = 4.5MPa ,故满足要求。挡土墙设计(1)挡土墙横断面布置,拟定断面尺寸墙高 H=4.8m,断面形式为俯视,墙顶宽度为 50cm,基础埋置深度为 0.8m.(二)车辆荷载换算当 H £ 2m 时, q = 20.0KPa ;当 H ³ 10m 时, q = 10KPaæ 5.8 - 2 öè 10 - 2 ø换算均布土层厚度: h0 =?qr?=?15. 2518?= 0.84m(三).主动土压力计算(假设破裂面交于荷载中部)(1)破裂角q由a = -14°,j = 35°,d =?j2?= 17.5°得:y = j + a + d = 35° -14° +17.5° = 38.5° A0 =?12?(a + H + 2h0)(a + H ) =?12?(2 + 4.8 + 2 ´ 0.84)(2 + 4.8) = 29.24B0 =?12?ab + (b + d )h0 -?12?H (H + 2a + 2h0) tan a´ 2 ´ 3 + (3 + 0.5) ´ 0.9 -?´ 4.8 ´ (4.8 + 2 ´ 2 + 2 ´ 0.84) ´ tan(-14°)=?12?12= 12.49