某高速公路隧道荷載-結(jié)構(gòu)法二襯受力計(jì)算案例1.1仰拱施作前二襯受力計(jì)算本設(shè)計(jì)所用C30混凝土，根據(jù)前述隧道截面形式及其尺寸，圍巖壓力及其荷載組合，采用二襯2D簡化模型，并運(yùn)用荷載-結(jié)構(gòu)法中的彈性地基梁（含曲梁及圓環(huán)）法進(jìn)行建模分析。二次襯砌以1D梁單元建立模型，進(jìn)行受力分析，此處剔除了仰拱影響，且拱腳采用了固結(jié)形式。計(jì)算數(shù)值結(jié)果如下：圖5-1軸力圖圖5-2剪力圖圖5-3彎矩圖軸力、剪力、彎矩導(dǎo)出結(jié)果如表5-1表5-1梁單元導(dǎo)出內(nèi)力數(shù)據(jù)表號(hào)單元X(m)Y(m)軸力(kN)剪力(kN)彎矩(kN·m)11-8.50244279.32581-2631.089143.02024.46134422-8.49581579.72327-2620.18140.5804532.9565933-8.49152278.9642-2647.954290.6451-54.8116444-8.45899980.15486-2604.433-8.13466340.5946455-8.42222578.48891-2694.553166.5035-167.456866-8.38606280.58183-2588.573-50.6921830.1917477-8.27751981.00116-2572.455-88.743913.83871288-8.21905377.9292-2716.869-228.4582-287.117699-8.13413881.4099-2556.146-123.1277-36.750021010-7.95693381.80514-2539.79-152.6434-89.356541111-7.86551677.45007-2621.136-701.1525-164.68411212-7.74715482.18411-2523.378-172.9698-149.90931313-7.50628682.54412-2506.438-171.7652-210.74291414-7.39063377.09085-2380.43-1294.915250.77821515-7.2360382.88262-2487.647-148.0969-258.60911616-6.93829783.19723-2464.434-72.47295-272.70241717-6.64216883.46931-2439.8464.900301-257.67291818-6.35656383.7062-2414.00120.94656-236.38211919-6.06251683.93251-2388.13534.42088-209.79022020-1.76041984.14797-2362.45441.36269-178.84422121-1.45067384.35227-2337.1653.82692-144.47222222-1.13368984.54515-2312.4559.8835-107.57782323-4.80988784.72636-2288.51463.617-69.034562424-4.47969884.89565-2261.53361.12597-29.680822525-4.1435681.05279-2243.6864.522379.6853682626-3.80192181.19759-2223.11861.9308448.3112727-3.45523281.32984-2204.00157.4879281.492632828-3.10395581.44937-2186.4751.34124120.58062929-2.74855681.55602-2170.65443.64858152.98273030-2.38950881.64965-2156.66734.57697182.16813131-2.02728681.73014-2144.61524.30163207.67013232-1.66237281.79738-2134.58313.00497229.0893333-1.29525181.85128-2126.6460.8754841246.09453434-0.9264181.89176-2120.863-11.89338258.42773535-0.556338581.91878-2117.276-21.10433261.90263636-0.185528381.9323-2111.913-38.55743268.407137370.185528481.9323-2116.764-52.05112261.903938380.556338981.91878-2119.867-61.3848258.4339390.926410681.89176-2121.182-78.35671246.097440401.29525281.85128-2132.671-90.76814229.092341411.66237481.79738-2142.285-102.4236207.673542422.02728881.73014-2153.955-113.1321182.171343432.3895181.64965-2167.602-122.708152.985444442.74855881.55602-2183.127-130.9727120.582445453.10395781.44936-2200.423-137.754881.4933646463.45523481.32983-2219.366-142.892148.310347473.80192381.19758-2239.819-146.23189.68295548484.14356381.05279-2261.636-147.632-29.6852449494.47970184.89564-2284.657-146.9621-69.0412850504.8098984.72636-2308.714-144.104-107.587151511.13369284.54515-2333.628-138.9525-144.484352521.45067784.35227-2359.213-131.4162-178.859553531.76042384.14796-2381.276-121.418-209.808854546.0625283.93251-2411.617-108.8958-236.404455556.35656783.70619-2438.03-93.80251-257.69956566.64217283.46931-2464.308-76.10697-272.732857576.93830983.19721-2493.548-7.372704-258.600358587.23605682.88256-2516.87272.76989-210.707159597.39063377.09084-2413.7281286.031027.20360607.50632382.54401-2531.046104.8921-149.858661617.74719882.18396-2550.667106.3692-89.3009662627.86551677.45007-2661.68671.9269250.788663637.95697981.80495-2561.09690.02097-36.6976664648.13418481.40966-2578.87164.083273.88112865658.21905377.9292-2753.032178.5475-164.677466668.27756181.00088-2592.07432.7825530.2176267678.38609680.5815-2604.653-2.76168840.5961568688.42222578.48891-2716.457-231.2465-287.119469698.45902280.15449-2616.646-43.4507132.9235170708.4915278.96409-2654.836-331.9878-167.473371718.49582379.72286-2628.309-90.984.38062172728.5024479.32549-2640.709-184.7192-54.89883與手算假定抗力法結(jié)果對(duì)比及討論：計(jì)算結(jié)果與上述手算假定抗力法結(jié)果對(duì)比，拱頂與側(cè)墻的數(shù)值相差比較大，但不能說哪種算法的結(jié)果一定準(zhǔn)確。首先，兩者計(jì)算所使用的原理雖都屬于荷載結(jié)構(gòu)法范疇，但仍有不同，手算采用的是假定抗力法，而軟件模擬類型屬彈性地基梁（含曲墻及圓環(huán)）法。在此指出兩種方法存在的誤差，假定抗力法采用結(jié)構(gòu)力學(xué)方法將洞室的側(cè)向土壓力、豎向土壓力及圍巖反作用的抗力分別計(jì)算出對(duì)洞室支護(hù)結(jié)構(gòu)的受力效果后進(jìn)行耦合，以求得最后的受力圖，該方法思路縝密，也符合科學(xué)的受力規(guī)律，合理運(yùn)用結(jié)構(gòu)力學(xué)基礎(chǔ)原理，且計(jì)算比較簡便，使工程師容易接受。但是，有些系統(tǒng)誤差無法去除，如人為憑經(jīng)驗(yàn)假定抗力起始點(diǎn)及抗力最大點(diǎn)的位置，這使得結(jié)果隨結(jié)構(gòu)分算單元的裂縫位置的不同而有所不同。利用MIDASGTS進(jìn)行計(jì)算的結(jié)果也存在很多誤差，限于作者水平，難以模擬較手算基本一致的模型，如難以模擬此類結(jié)構(gòu)——在拱墻傳下的軸力和彎矩作用下，拱墻底彈性支座產(chǎn)生相應(yīng)剛性位移和轉(zhuǎn)角，而墻本身只發(fā)生相應(yīng)的豎向沉陷和轉(zhuǎn)角。即無法模擬像手算一樣的合理的邊墻與拱腳彈性支座的變形協(xié)調(diào)條件（如圖5-4）。本次計(jì)算是直接將拱腳擬以固定支座，違背了手算的假定。加上其他原因，這也就使得與手算結(jié)果有較大差距。圖5-4拱腳彈性支座1.2仰拱施作后二襯受力計(jì)算在本設(shè)計(jì)中綜合考慮仰拱施作后最終的受力情況，并以設(shè)置仰拱后受力情況進(jìn)行支護(hù)結(jié)構(gòu)配筋驗(yàn)算，計(jì)算結(jié)果如下所述。計(jì)算受力結(jié)果圖如下：圖5-5施加仰拱后的軸力圖圖5-6施加仰拱后的剪力圖圖5-7施加仰拱后的彎矩圖施加仰拱后導(dǎo)出數(shù)值結(jié)果如表5-2表5-2施加仰拱后梁單元內(nèi)力數(shù)據(jù)表號(hào)單元X(m)Y(m)軸力(kN)剪力(kN)彎矩(kN·m)11-8.30248779.32869-2461.085122.488651.8896822-8.29617779.71467-2448.2243.31912267.3456933-8.29175178.97325-2473.363279.72661.05568244-8.26078880.12952-2437.021-61.652650.302255-8.2284178.5291-2521.551199.553-101.659966-8.1906880.53993-2427.41-124.81898.98087977-8.08634780.943-2418.945-176.217-53.254188-8.04458878.0227-2573.575-31.67712-226.23699-7.94852781.33588-2411.332-219.1016-132.74021010-7.77819481.7158-2404.131-248.5302-223.77071111-7.72472177.58919-2578.273-203.1528-219.10931212-7.57655182.08007-2396.34-254.2167-316.37081313-7.34502582.42612-2381.896-219.7958-393.76651414-7.29506577.26418-2534.732-377.6396-111.72141515-7.0852582.75149-2369.15-122.7903-429.83961616-6.79906483.0539-2343.092-0.1911313-413.91071717-6.71705177.01181-2514.574-250.977987.65881818-6.51172783.31775-2314.85171.14038-371.33051919-6.23173183.54998-2287.14784.01907-331.77042020-6.03358976.78219-2540.02120.77623268.65292121-1.94345983.77185-2259.52994.29202-284.18382222-1.64729483.98307-2232.2102.0018-233.51022323-1.34363184.18337-2201.364107.2063-180.66942424-1.34230276.57733-2569.271113.3747254.3722525-1.03287184.37246-2179.213109.9781-126.55612626-4.71542984.55011-2153.937110.4043-72.034612727-4.64408776.3975-2597.31113.6342173.94082828-4.39172484.71607-2129.716108.5859-17.934012929-4.06218884.87013-2106.723104.637134.957143030-3.9398576.24292-2621.76680.6662693.875753131-3.72725781.01208-2081.11998.6843681.895123232-3.38737781.14173-2061.05790.86621134.18553333-3.23050476.11379-2641.91241.8475438.063873434-3.04299981.25892-2046.67681.33192179.18723535-2.69457981.36347-2030.10570.24086220.31613636-2.51696976.01029-2657.81421.157817.7636243737-2.34258281.45527-2011.45857.76146257.04873838-1.98747481.53418-2002.83944.0703288.9253939-1.8001771.93255-2669.7978.008027-4.4074024040-1.62972681.60009-1992.33229.35098311.55094141-1.26981581.65293-1984.01313.79315336.60124242-1.08103771.88066-2678.1723.534771-6.8507164343-0.908216881.69263-1977.939-2.408681351.82064444-0.54541381.71912-1974.153-19.0562361.02594545-0.360501471.8547-2683.1493.989949-1.9041684646-0.181884881.73237-1972.681-31.9485364.106747470.181884881.73237-1973.527-52.88336361.026148480.360501471.8547-2684.8241.932979-1.20359749490.54541381.71912-1976.704-69.65813351.820950500.908216881.69263-1982.184-86.07086336.601551511.08103771.88066-2683.1886.160032-1.90418352521.26981581.65293-1989.931-101.9218311.551253531.62972681.60009-1999.894-117.0145288.92554541.8001771.93255-2678.1311.231653-6.85076155551.98747481.53418-2012.006-131.1567257.048456562.34258281.45527-2026.188-144.1618220.315257572.51696976.01029-2669.426-12.598-4.40749958582.69457981.36347-2042.345-151.8496179.185759593.04299981.25892-2060.366-166.0476134.183360603.23050476.11379-2656.746-38.189037.76345161613.38737781.14173-2080.13-174.591881.8920262623.72725781.01208-2101.502-181.328134.9530663633.9398576.24292-2639.752-74.1260338.0636364644.06218884.87013-2124.337-186.1124-17.9391965654.39172484.71607-2148.475-188.8123-72.0410266664.64408776.3975-2618.361-108.423893.875567674.71542984.55011-2173.75-189.3076-126.563868681.03287184.37246-2199.985-187.4908-180.678669691.34230276.57733-2593.288-109.6991173.940870701.34363184.18337-2226.994-183.2679-233.52171711.64729483.98307-2254.585-176.5592-284.196272721.94345983.77185-2282.56-167.2996-331.784673736.03358976.78219-2566.89-18.83294254.372574746.23173183.54