基于碳排放评价的超小净距隧道绿色施工优化研究

为推进生态文明社会建设发展，倡导绿色低碳施工理念，以碳排放评价作为切入点，开展了超小净距隧道绿色施工优化研究。依托贵州旧屋基原连拱隧道段工程，基于隧道施工碳排放模型，归纳了影响隧道施工碳排放量的直接影响因素和间接影响因素。综合分析认为，造成隧道施工碳排放量产生的主要因素为施工过程中的机械运作以及建筑材料生产，因此从缩短工期与优化结构形式2条技术路径对原方案进行绿色低碳施工优化具有可行性，进而提出分离式超小净距隧道优化方案，并将原CD开挖工法调整为“先行洞台阶法+后行洞超前小导洞扩挖工法”。采用数值模拟方法分析了不同中岩柱加固方法下超小净距隧道安全性，确定了中岩柱“中空注浆锚杆加固+三角区小导管注浆加固”的辅助加固方案。根据现场试验段监测数据，优化方案相比原方案施工工期缩短15 d，拱顶沉降最大值13.5 mm，收敛变形最大值9.53 mm，初支安全系数最小值2.13，满足支护结构安全性要求。基于碳排放系数法，对比分析了优化前后施工方案的碳排放量，结果表明：优化方案的总碳排放量相较于原方案减少25.43％，其中通过节省原材料减少碳排放量最为明显，减少碳排放量为30.14%，绿色低碳实施效果显著，对类似超小净距隧道施工的节能减排优化具有一定的参考意义。

Green Construction Optimization of Ultrasmall Clearance Tunnel Based on Carbon Emission Evaluation

A carbon emission evaluation method was used in this study to investigate the optimization of ultrasmall clear-distance tunnel construction to promote the development of an ecologically civilized society and advocate the green and low-carbon concept. The original continuous arch tunnel section project of the Jiuwuji tunnel in Guizhou Province was studied. Based on the model of tunnel construction carbon emission, the direct and indirect factors influencing the carbon emissions of tunnel construction were summarized. From a comprehensive analysis, the main factors causing carbon emissions of tunnel construction are the mechanical operation and production of construction materials during construction. Thus, it was feasible to optimize the green and low-carbon construction from two technical paths:shortening the construction period and optimizing the structural form. Next, an optimization plan for the separated ultrasmall clearance tunnel was proposed, and the original central diaphragm excavation method was adjusted to the method of "first cave step method + back cave overrun small guide cave." Numerical simulations were performed to analyze the safety of the tunnel using different reinforcement techniques of the rock column, and the reinforcement scheme, "hollow grouting anchor reinforcement + triangular small conduit grouting reinforcement," was adopted. Based on the monitoring data of the field test section, the construction period of the optimized plan decreases by 15 days compared with that of the original plan. The maximum values of the arch settlement and convergence deformation are 13.5 and 9.53 mm, respectively, and the minimum value of the initial support safety factor is 2.13, which satisfies the safety requirements of the support structure. Based on the carbon emission coefficient method, the carbon emissions of the construction scheme before and after optimization were compared and analyzed. The results show that the total carbon emissions of the optimized scheme decrease by 25.43% compared with those of the original scheme, among which the carbon emissions are most evidently reduced by saving raw materials, which decreases by 30.14%. The findings are significant for optimizing energy savings and emission reduction for similar ultrasmall clearance tunnel construction.