The impact of soft and hard rock on engineering construction can be illustrated by several specific cases. Here are some examples that show the challenges and solutions faced by engineering construction under different types of rock conditions:

   Hard Rock Cases:

   1. Gotthard Base Tunnel in Switzerland: This world's longest railway tunnel passes through the hard rock of the Alps. During construction, engineers faced extreme geological conditions, including hard rock layers and fault zones. To meet these challenges, they used advanced tunnel boring machines (TBMs) and blasting technologies, and implemented strict safety management and monitoring systems.

   2. Hoover Dam in the United States: Located on the Colorado River, the Hoover Dam's foundation is made of hard volcanic rock. During construction, engineers took advantage of the high bearing capacity and stability of the rock, but also had to deal with the difficulties of excavation due to the hardness of the rock. They used precisely controlled blasting techniques and drilling operations to ensure the quality and safety of the dam's foundation.

   Soft rock cases:

   1. Hong Kong International Airport reclamation project: In the construction of Hong Kong International Airport, due to the complex geological conditions, including weak mudstone and siltstone, engineers adopted large-scale seabed reclamation technology, combined with deep mixing piles and prefabricated caissons and other measures to reinforce the foundation, ensuring the stability of the airport runway and facilities.

   2. Tokyo Metro Construction in Japan: Tokyo Metro encountered weak sedimentary rocks and clay rocks in some areas, which led to settlement problems during construction. To solve this problem, engineers adopted a method of gradual excavation and immediate support, as well as frozen soil technology to temporarily reinforce the fragile strata.

  Comprehensive cases:

   1. China Three Gorges Dam: The construction of the Three Gorges Dam involved a variety of geological conditions, including soft and hard rocks. In the dam foundation treatment, engineers took corresponding reinforcement measures for different rock types, such as using concrete grouting and anchor reinforcement in soft rock areas, and focusing on drainage and crack treatment in hard rock areas.

   These cases demonstrate the specific impacts of soft and hard rock on engineering construction, and how engineers can overcome these challenges through innovative technologies and management strategies to ensure the success and safety of the project. Each engineering project has its own unique geological conditions and environmental background, so the solution must also be customized to suit specific engineering needs.