Boutique Canlon | Qingdao Jiaozhou Shaohai Xiyuan Road Underground Tunnel Project

A Review of Canlon's Premium Projects – Qingdao Shaohai Xiyuan Road Underground Tunnel Project

Summary

Waterproofing systems are the "lifeline" of underground tunnel projects, directly determining the structural durability and operational safety of the engineering structure. The Qingdao Shaohai Xiyuan Road Underground Tunnel, a key transportation hub connecting the North and South Lake areas of Jiaozhou Shaohai, faced multiple challenges, including soft soil geology, construction across a lake, and complex node handling. Canlon achieved the "no seepage, no leakage" quality target in this waterproofing project through technological innovation and meticulous management, creating a typical example in the field of waterproofing for underground transportation engineering.

Project Overview

The Qingdao Shaohai Xiyuan Road Underground Tunnel Project, constructed by the Qingdao Daguhe Provincial Ecological Tourism Resort Management Committee and undertaken by China 22nd Metallurgical Construction Corporation Shandong Branch, stretches from Zhanqian Avenue in the west to Shaohai North Road in the east. It encompasses underground roads, surface roads, and bridge upgrades, with the underground tunnel section traversing a sensitive area between the North and South Lakes of Shaohai. The project's geology is primarily composed of silt and thick sand layers, and includes cofferdam construction for the lake-crossing section. The waterproofing on the tunnel exterior is directly attached to the leveling layer of the support piles. Construction joint spacing is 25 to 30 meters, and expansion joint spacing is 50 to 60 meters. Combined with complex nodes such as lattice columns penetrating the roof slab, this places stringent demands on the adaptability and reliability of the waterproofing system. To achieve the dual goals of long-term structural waterproofing and ecological protection, the project adopts an integrated waterproofing solution combining customized materials, innovative processes, and intelligent management, covering the entire tunnel structure, node sealing, and auxiliary structures.

Core waterproofing challenges

1. Leakage risk in complex geological conditions:

The tunnel passes through a thick layer of silt and sand. This type of stratum is highly permeable and has poor stability. During construction, the hole is prone to collapse, which can lead to the deviation of the concrete pouring. In addition, the verticality deviation of the support piles, which serve as the outer formwork of the main side wall, directly affects the adhesion of the waterproof layer and creates potential leakage channels.

2. The sealing challenge of dense nodes:

The project includes numerous construction joints, expansion joints, and lattice columns penetrating the roof slab. There are construction joints every 25 to 30 meters. Stress is concentrated at these joints, and the structural interfaces are complex. Traditional sealing methods are difficult to adapt to the settlement and deformation requirements. Cutting the lattice columns presents an even greater challenge in stopping water leakage.

3. Quality interference from overlapping operations:

With only 4 meters between the foundation pit supports, the waterproofing construction was carried out concurrently with the installation of steel supports and steel walers, resulting in frequent joints of the membrane. Improper connection of the procedures could easily cause damage to the waterproof layer. Furthermore, the construction of the cofferdam in the lake crossing section needed to take into account both waterproofing performance and ecological protection, further increasing the complexity of the construction.

Customized waterproofing solutions

1. Main waterproofing system:

The "pre-applied reverse-adhesive waterproofing technology for underground engineering" is adopted, using "Canlon" MBP-P polymer self-adhesive membrane pre-applied waterproofing membrane + MBP-W polymer self-adhesive waterproofing membrane as the main waterproofing layer system. This waterproofing system is constructed using the "pre-applied reverse-adhesive method," laid loosely on the base layer, which can form a strong bond with the subsequently poured concrete, effectively resisting the settlement and deformation of the base layer. Even if the waterproofing layer is partially damaged, the reverse-adhesive properties can prevent water seepage. On the surface of the leveling layer of the support piles, a cement-based penetrating crystalline waterproofing material is used in conjunction. Its active ingredients crystallize upon contact with water, penetrating deep into the capillary pores of the concrete to achieve self-healing waterproofing, forming a "double barrier" with the membrane.

2. Node sealing material:

For construction joints and expansion joints, a combination of "rubber waterstop + sealant" is adopted. The waterstop is made of aging-resistant and highly elastic material and is pre-embedded to ensure synchronous deformation with the structure. The expansion joint gaps are filled with flexible sealant, which has both adhesion and extensibility to adapt to differences in ground settlement. At the locations where the lattice columns penetrate the roof slab, custom-made metal waterstop rings and water-swellable rubber rings are used to form a multi-layered sealing structure to block vertical leakage paths.

3. Quality interference from overlapping operations:

With only 4 meters between the foundation pit supports, the waterproofing construction was carried out concurrently with the installation of steel supports and steel walers, resulting in frequent joints of the rolled material. Improper connection of the procedures could easily cause damage to the waterproof layer. Furthermore, the construction of the cofferdam in the lake crossing section needed to take into account both waterproofing performance and ecological protection, further increasing the complexity of the construction.

During construction, the technical team of Canlon implemented a refined construction process for different scenarios. For potential leakage channels, a four-step process of "base pretreatment - membrane laying - bonding reinforcement - protective layer construction" was executed. For complex nodes, special treatment processes were applied. At the same time, cross-operation protection measures were implemented . The construction process was optimized through BIM technology, clarifying the time interval and spatial avoidance plan between waterproofing construction and steel support installation. Temporary protective layers were used to cover the laid membrane to avoid damage from mechanical collisions. During the construction of the cofferdam in the lake crossing section, impermeable geomembrane was laid simultaneously to form a continuous sealing system with the tunnel waterproofing layer, taking into account both waterproofing and ecological isolation requirements.

Implementation Results and Industry Value

The project's waterproofing work underwent comprehensive testing and achieved the goal of "zero leakage." No leakage points were found in the main tunnel structure or joints. The cement-based penetrating crystalline material formed obvious crystalline seals at local concrete cracks, demonstrating excellent self-healing properties. After six months of follow-up monitoring, the bonding strength of the pre-applied reverse-adhesive waterproof layer remained stable, and there was no sealing failure even when the expansion joints experienced a maximum expansion of 30 mm. The waterproofing effect at the lattice column penetration points withstood the test of high water levels during heavy rains. The cofferdam seepage prevention system in the lake-crossing section effectively prevented lake water from seeping into the construction area without polluting the surrounding water bodies, achieving a win-win situation for waterproofing and ecological protection.

This project marks the industry's first integrated application of "pre-applied anti-adhesion technology + crystalline materials + BIM management" in a lake-crossing underground tunnel. Its waterproofing solution for soft soil provides replicable experience for similar projects. The project's developed grid column joint water-stopping technology and dense construction joint treatment scheme effectively solved the sealing problem of complex joints in underground engineering, filling a gap in regional soft soil tunnel joint waterproofing technology. Simultaneously, its "sample guidance + three-level testing + intelligent traceability" quality management model provides a standardized paradigm for underground engineering waterproofing quality control, demonstrating the practical value of technology empowering waterproofing projects.