This paper proposes an environmental assessment approach consistent with sustainable development principles in the design of underground structures. A literature review highlighted the methods applicable at the project construction stage for buildings or road infrastructure that may specifically be intended for the underground. An underground assessment was developed and implemented for the urban case study of a multimodal tunnel open to soft modes, such as pedestrians, bikes and buses, as well as to conventional road modes.

A Life Cycle Assessment (LCA) was performed using and combining three methods (CED, EDIP, CML), in yielding 17 indicators. Two distinct scenarios were investigated when upgrading the safety of the existing road tunnel by allowing for evacuations in case of an emergency. The first (Scenario 1) consists of the construction and operation of a simple safety gallery, while the second (Scenario 2) consists of the construction and operation of a new tunnel dedicated to soft modes that can also be used as a safety gallery.

The impact assessment results showed that variations in the set of indicators in Scenario 2, compared to those of Scenario 1 were significant enough to allow for a more refined comparison between the two scenarios. In addition, the contributions of the operation phase to the total impacts were examined. The relative weight of the construction phase was discussed with respect to the underground solution. This study was then able to point out that the Life Cycle Assessment is a powerful environmental assessment method for a comparative study of various urban development scenarios, including underground facilities, as of the early project stages.

本文提出了一种在地下结构设计中符合可持续发展原则的环境评估方法。文献综述强调了在项目施工阶段适用于建筑物或道路基础设施的方法，这些方法可能专门用于地下。为城市案例研究开发并实施了地下评估，该城市案例研究了对多模式隧道开放的软模式，例如行人，自行车和公共汽车，以及常规道路模式。

使用并结合三种方法（CED，EDIP，CML）进行了生命周期评估（LCA），得出了17项指标。在紧急情况下允许疏散以提高现有公路隧道的安全性时，研究了两种截然不同的方案。第一个（方案1）由一个简单的安全通道的构造和运行组成，而第二个（方案2）由一个专用于软模式的新隧道的构建和操作组成，该通道也可以用作安全通道。

影响评估结果表明，与方案1相比，方案2中的指标集差异显着，足以使这两种方案之间的比较更为精确。此外，还检查了运营阶段对总体影响的贡献。关于地下解决方案，讨论了施工阶段的相对重量。然后，该研究可以指出，生命周期评估是一种强大的环境评估方法，可用于比较项目初期的各种城市发展情景，包括地下设施。