《隧道襯砌內(nèi)力及配筋驗(yàn)算案例》3300字

隧道襯砌內(nèi)力及配筋驗(yàn)算案例根據(jù)地質(zhì)勘察揭示的隧道圍巖分級(jí)，本隧道以Ⅲ、Ⅳ、Ⅴ級(jí)圍巖為主，根據(jù)最不利和主要隧道圍巖條件，選取隧道左線圍巖3個(gè)斷面進(jìn)行計(jì)算分析，分別為：①進(jìn)出口段淺埋段（ZK27+820、Ⅴ級(jí)圍巖斷面，埋深12m）；②深埋段（ZK28+260，最大埋深640m、Ⅳ級(jí)圍巖斷面）；③洞身段（ZK29+300，埋深313m、Ⅲ級(jí)圍巖斷面）根據(jù)這三個(gè)斷面作為內(nèi)力計(jì)算代表性斷面并進(jìn)行全隧道襯砌配筋計(jì)算，荷載計(jì)算如下：圖1計(jì)算斷面選取位置（單位：m）1襯砌結(jié)構(gòu)計(jì)算1.1計(jì)算參數(shù)本公路隧道以Ⅲ、Ⅳ、Ⅴ級(jí)圍巖為主，參數(shù)指標(biāo)選取如表5-1：表5-1圍巖物理力學(xué)參數(shù)取值圍巖級(jí)別重度彈性抗力系數(shù)變形模量泊松比μ內(nèi)摩擦角粘聚力計(jì)算摩擦角Ⅲ24800100.25400.860Ⅳ2030020.3300.350Ⅴ181501.50.4250.1401.2內(nèi)力計(jì)算（1）隧道深淺埋判定深淺埋隧道判定按以下公式：式中：；；根據(jù)本次隧道斷面設(shè)計(jì)，開(kāi)挖跨度考慮隧道襯砌及超挖效應(yīng)后，毛洞按13.0m計(jì)算：本隧道Ⅲ級(jí)圍巖：Ⅳ級(jí)圍巖：Ⅴ級(jí)圍巖：本公路隧道Ⅲ級(jí)最大埋深圍巖埋深313m，大于臨界深度6.48m，按深埋圍巖壓力計(jì)算；Ⅳ級(jí)圍巖埋深640m大于臨界深度兩側(cè)，按深埋隧道考慮；進(jìn)口段Ⅴ級(jí)圍巖埋深12m均小于Hp和hq，按超淺埋圍巖壓力計(jì)算。1.3各級(jí)圍巖壓力計(jì)算（1）斷面2：Ⅲ級(jí)圍巖最大埋深隧道圍巖壓力計(jì)算根據(jù)《公路隧道設(shè)計(jì)規(guī)范》（JTGD70－2004），計(jì)算圍巖壓力：①②（2）斷面3：Ⅳ級(jí)圍巖深埋隧道圍巖壓力計(jì)算：①②（3）斷面1：Ⅴ級(jí)圍巖淺埋隧道（洞口段）圍巖壓力計(jì)算①式中：H－隧道坑頂至地面的距離(m)，此處取等效荷載高度8m。解得：②側(cè)向壓力按均布考慮：2襯砌內(nèi)力計(jì)算2.1斷面1：Ⅴ級(jí)圍巖淺埋(洞口淺埋段)1.建模取隧道二次襯砌中軸線。2.定義材料（1）定義單元類型荷載-結(jié)構(gòu)模型中的二次襯砌采用梁?jiǎn)卧舅淼涝O(shè)計(jì)計(jì)算采用Beam3單元類型，計(jì)算后可直接讀取彎矩與軸力。（2）設(shè)置單元實(shí)常數(shù)；；。（3）定義材料特性；；。3.施加約束對(duì)于圍巖彈性反力進(jìn)行模擬，施加徑向桿單元，選擇Link10單元，長(zhǎng)度為1m，彈性模量，將桿單元外端采用固端約束。通過(guò)計(jì)算得出的襯砌內(nèi)力，將垂直、水平的面荷載轉(zhuǎn)換為節(jié)點(diǎn)荷載并將荷載施加到模型中，將荷載添加到每個(gè)單元：圖5-2節(jié)點(diǎn)荷載圖4.求解及計(jì)算結(jié)果分析（1）變形圖圖5-3變形圖軸力圖圖5-4軸力圖(N)（3）剪力圖圖5-5剪力圖(N)（4）彎矩圖圖5-6彎矩圖(N?m)依據(jù)數(shù)值分析計(jì)算結(jié)果，安全系數(shù)計(jì)算根據(jù)《公路隧道設(shè)計(jì)規(guī)范》（JTGD3370.1—2018）規(guī)定，按下式檢算。當(dāng)由抗壓強(qiáng)度控制，即QUOTEQUOTEe=MN≤0.2he=MN≤0.2h時(shí)式中：K——混凝土結(jié)構(gòu)強(qiáng)度安全系數(shù)；N——軸向力，kN；φ——構(gòu)件的縱向彎曲系數(shù)，對(duì)于隧道襯砌，可取φ=1；α——軸向力的偏心影響系數(shù),按附注多項(xiàng)式計(jì)算得到；b——截面寬度，m（通常取1m）；h——截面厚度；e——計(jì)算截面的偏心距（m），QUOTEe=MNe=MNy——計(jì)算截面重心至受壓邊緣的距離（m）；——混凝土抗壓極限強(qiáng)度，kPa。當(dāng)由抗拉強(qiáng)度控制，即QUOTEQUOTEe=MN≥0.2he=MN≥0.2h時(shí)式中：——混凝土抗拉極限強(qiáng)度，kPa。各單元截面（共計(jì)48個(gè)單元）安全系數(shù)計(jì)算如下表2。單元號(hào)分布表2內(nèi)力及安全系數(shù)單元號(hào)彎矩（N-m）軸力（N)偏心距e偏心影響系數(shù)α安全系數(shù)K1-38E+05-1.77E+060.3040.871.82-1.92E+05-1.71E+060.1120.837.231084.1-1.67E+060.0011.008.8465989-1.66E+060.0400.988.7542640-1.64E+060.0260.998.96-34818-1.61E+060.0220.999.17-1.39E+05-1.58E+060.0880.898.38-2.36E+05-1.52E+060.1550.706.89-2.65E+05-1.44E+060.1840.596.110-2.21E+05-1.36E+060.1630.687.411-1.26E+05-1.26E+060.1000.8610.112-6203.3-1.18E+060.0051.0012.5131.16E+05-1.11E+060.1050.8511.4142.19E+05-1.05E+060.2080.766.4152.87E+05-1.02E+060.2800.669.5163.11E+05-1.02E+060.3040.9121.8172.87E+05-1.05E+060.2730.876.6182.18E+05-1.10E+060.1980.526.9191.15E+05-1.17E+060.0980.8710.920-6372-1.26E+060.0051.0011.721-1.26E+05-1.35E+060.0930.889.622-2.21E+05-1.44E+060.1530.717.323-2.65E+05-1.51E+060.1750.636.224-2.36E+05-1.57E+060.1500.726.825-1.39E+05-1.61E+060.0860.898.226-34745-1.63E+060.0210.999.02742674-1.65E+060.0260.998.92865998-1.66E+060.0400.988.6291092.7-1.70E+060.0011.008.730-1.92E+05-1.76E+060.1090.842.031-1.38E+05-1.75E+060.0790.917.732-35139-1.74E+060.0200.998.4332.07E+05-1.74E+060.1190.816.9342.72E+05-1.75E+060.1550.716.0352.41E+05-1.76E+060.1370.766.4361.73E+05-1.77E+060.0970.873.2371.02E+05-1.78E+060.0570.957.93846526-1.79E+060.0260.998.23912011-1.79E+060.0071.008.240449.5-1.79E+060.0001.008.24112015-1.79E+060.0071.008.24246549-1.78E+060.0260.998.2431.02E+05-1.77E+060.0580.957.9441.73E+05-1.76E+060.0980.877.2452.41E+05-1.75E+060.1380.766.4462.72E+05-1.74E+060.1560.706.0472.08E+05-1.74E+060.1190.816.948-34536-1.76E+060.0200.998.4由以上結(jié)果可知，襯砌某些少數(shù)部位的安全系數(shù)小于規(guī)范規(guī)定值，因此需要配筋以滿足結(jié)構(gòu)安全。2.2斷面2：Ⅳ級(jí)圍巖最大深埋1.建模取隧道二次襯砌中軸線。2.定義材料（1）定義單元類型荷載-結(jié)構(gòu)模型中的二次襯砌采用梁?jiǎn)卧舅淼涝O(shè)計(jì)計(jì)算采用Beam3單元類型，計(jì)算后可直接讀取彎矩與軸力。（2）設(shè)置單元實(shí)常數(shù)；；。（3）定義材料特性；；。3.施加約束對(duì)于圍巖彈性反力進(jìn)行模擬，施加徑向桿單元，選擇Link10單元，長(zhǎng)度為1m，彈性模量，將桿單元外端采用固端約束。通過(guò)計(jì)算得出的襯砌內(nèi)力，將垂直、水平的面荷載轉(zhuǎn)換為節(jié)點(diǎn)荷載并將荷載施加到模型中，如下表所示，將荷載添加到每個(gè)單元：圖5-7節(jié)點(diǎn)荷載圖4.求解及計(jì)算結(jié)果分析（1）變形圖圖5-8變形圖（2）軸力圖圖5-9軸力圖(N)（3）剪力圖圖5-10剪力圖(N)（4）彎矩圖圖5-11彎矩圖(N?m)各單元截面（共計(jì)48個(gè)單元）安全系數(shù)計(jì)算如下表3。表3內(nèi)力及安全系數(shù)單元號(hào)彎矩（N-m）軸力（N)偏心距e偏心影響系數(shù)α安全系數(shù)K1-2.74E+05-9.00E+050.3050.515.52-98074-8.65E+050.1130.8314.1350.37-8.44E+050.0001.0017.5433216-8.33E+050.0400.9817.3521406-8.22E+050.0260.9917.76-18049-8.07E+050.0220.9918.17-71094-7.86E+050.0900.8816.68-1.20E+05-7.56E+050.1590.6913.59-1.33E+05-7.17E+050.1860.5912.010-1.10E+05-6.72E+050.1640.6814.811-62338-6.26E+050.1000.8620.312-2411.6-5.83E+050.0041.00231358201-5.46E+050.1060.8522.8141.09E+05-20E+050.2100.4412.4151.43E+05-5.06E+050.2830.7512.0161.55E+05-5.06E+050.3070.678.7171.43E+05-19E+050.2760.5515.7181.09E+05-5.44E+050.2010.5013.61958124-5.80E+050.1000.8621.920-2494.8-6.23E+050.0041.0023.721-62413-6.68E+050.0930.8819.422-1.10E+05-7.12E+050.1540.7114.723-1.33E+05-7.51E+050.1770.6212.224-1.20E+05-7.80E+050.1540.7113.425-71043-8.01E+050.0890.8916.426-18013-8.16E+050.0220.9917.92721422-8.26E+050.0260.9917.72833219-8.37E+050.0400.9817.22954.183-8.58E+050.0001.0017.230-98047-8.93E+050.1100.8413.831-1.74E+05-8.91E+050.1950.538.832-17740-8.85E+050.0200.9916.6331.06E+05-8.86E+050.1190.8113.5341.39E+05-8.91E+050.1550.7111.7351.23E+05-8.98E+050.1370.7612.53688152-9.04E+050.0980.8714.23752268-9.09E+050.0580.9515.43823839-9.12E+050.0260.9916.0396253.2-9.14E+050.0071.0016.140362.85-9.14E+050.0001.0016.1416255.8-9.13E+050.0071.0016.14223852-9.09E+050.0260.9916.04352304-9.05E+050.0580.9515.54488232-8.99E+050.0980.8714.2451.23E+05-8.93E+050.1380.7612.6461.39E+05-8.88E+050.1560.7011.7471.06E+05-8.87E+050.1200.8113.548-17434-8.93E+050.0200.9916.4由以上結(jié)果可知，襯砌某些點(diǎn)處的的安全系數(shù)小于規(guī)范規(guī)定值，因此需要配筋以滿足結(jié)構(gòu)安全。2.3斷面3：Ⅲ級(jí)圍巖深埋段1.建模忽略底板取隧道二次襯砌中軸線。2.定義材料（1）定義單元類型荷載-結(jié)構(gòu)模型中的二次襯砌采用梁?jiǎn)卧舅淼涝O(shè)計(jì)計(jì)算采用Beam3單元類型，計(jì)算后可直接讀取彎矩與軸力。（2）設(shè)置單元實(shí)常數(shù)單元截面面積：；截面慣性矩：；截面高度：。（3）定義材料特性C30混凝土彈性模量；泊松比；材料密度：。3.施加約束模擬圍巖彈性反力，施加徑向桿單元，選擇Link10單元，長(zhǎng)度為1m，彈性模量，將桿單元外端采用固端約束，通過(guò)計(jì)算得出的襯砌內(nèi)力，將垂直、水平的面荷載轉(zhuǎn)換為節(jié)點(diǎn)荷載并將荷載施加到模型中，將荷載添加到每個(gè)單元：圖5-12模型示意圖4.求解及計(jì)算結(jié)果分析（1）變形圖圖5-13變形圖（2）軸力圖圖5-14軸力圖(N)（3）剪力圖圖5-15剪力圖(N)（4）彎矩圖圖5-16彎矩圖(N?m)挑選具有代表性的襯砌受力如拱底、拱頂?shù)冗M(jìn)行分析及計(jì)算，得到以下結(jié)果：表3節(jié)點(diǎn)內(nèi)力、安全系數(shù)表單元號(hào)彎矩（N-m）軸力（N)偏心距e偏心影響系數(shù)α安全系數(shù)K1-1.65E+05-5.46E+050.1030.9110.12-60765-24E+050.1160.8223.13-1753.4-10E+050.0031.0028.9418754-5.01E+050.0370.9828.8512183-4.91E+050.0250.9919.76-11479-4.79E+050.0240.9910.57-44036-4.64E+050.0950.8717.88-74846-4.43E+050.1690.6611.99-84738-4.17E+050.2030.4917.210-70697-3.87E+050.1830.602.811-40533-3.56E+050.1140.834.212-2232.5-3.27E+050.0071.005.01336650-3.03E+050.1210.819.31469561-2.86E+050.2430.1021551438-2.77E+050.1860.5811.11699087-2.76E+050.3590.925.81791418-2.85E+050.3210.9121869522-3.01E+050.2310.7612.51936600-3.25E+050.1130.8337.720-2286.8-3.52E+050.0061.0041.821-40582-3.82E+050.1060.8532.622-70730-4.12E+050.1720.6523.123-84745-4.37E+050.1940.5418.324-74817-4.58E+050.1630.6821.825-44003-4.73E+050.0930.8827.426-11456-4.85E+050.0240.9930.12712193-4.94E+050.0250.9929.62818755-5.03E+050.0370.9828.729-1751-17E+050.0031.0028.530-60746-39E+050.1130.8322.731-1.65E+05-36E+050.3080.727.332-8582.6-32E+050.0161.0027.63366517-32E+050.1250.8022.13485936-34E+050.1610.6919.03575840-37E+050.1410.7520.63654350-5.41E+050.1010.8623.53732199-5.43E+050.0590.9525.73814703-5.45E+050.0270.9926.7393897.6-5.46E+050.0071.0027.040281.49-5.46E+050.0011.0027.0413899.4-5.46E+050.0071.0027.04214711-5.44E+050.0270.9926.84332222-5.41E+050.0600.9525.84454399-38E+050.1010.8623.54575929-35E+050.1420.7520.64686073-33E+050.1610.6818.94766695-33E+050.1250.8022.048-8397-38E+050.0161.0027.3由以上結(jié)果可知，襯砌拱頂?shù)陌踩禂?shù)大