1. Product Summary
The Xia Gongla Mountain Tunnel is a 4,392-metre-long highway tunnel located in Banbar County of Qamdo City, Tibet Autonomous Region. It is a control project on China National Highway G349 and links Tsoka Town and Jinling Township with each other. Built across Xia Gongla Mountain, it provides drivers with a safer and more reliable highway passage through the high-altitude region.
Construction of the Xia Gongla Mountain Tunnel entailed excavating a single-bore, two-way highway tunnel. Project portal elevations are around 4,750 metres above sea level, presenting designers and contractors with difficult conditions including high altitude, low temperatures, seasonal snowfall, intricate mountain terrain and limited construction accessibility.
The tunnel opened to traffic in 2024 after about six years of construction. It eliminated the region’s previous reliance on a mountain road that experienced heavy snowfall and periodic closures.
2. Project Details
Project: Xia Gongla Mountain Tunnel
Location: Banbar County, Qamdo City Tibet, China
Highway: China National Highway G349
Tunnel Length: 4,392m
Portal Elevation: Around 4,750 metres
Tunnel Configuration: Single-bore, two-way traffic
Clear Width: 9 metres
Clear Hieight: 5 metres
Seismic Fortification Intensity: Grade VII
Application: High-altitude mountain highway tunnel
3. Project Details
Situated in an isolated mountainous region of eastern Tibet. Residents who lived on either side of the mountain – Tsoka Town and Jinling Township – relied on a steep mountain road prior to tunnel construction.
While a road across Xia Gongla Mountain had existed before, heavy snow and severe winter weather made the roadway impassable for months each year. Local transportation, farming activities and residents’ access to medical care all faced issues as a result of seasonal road closures.
Officials approved construction on the G349 Banbar–Lhari highway upgrading project in October 2018. The Xia Gongla Mountain Tunnel drives began that same month.
As it created a direct route through the mountain, the project became one of Tibet’s most significant transportation infrastructure projects. Regional drivers no longer need to cross Xia Gongla Mountain’s high and heavily weather-affected road.
4. Major Design and Construction Issues
4.1 High Altitude Environment
The elevations of the two tunnel portals are approximately 4,750 metres. At these heights oxygen deficiency could impact on personnel and influence the performance of machinery and construction productivity. Planning of equipment maintenance, material supply and management of personnel health were therefore important aspects throughout the construction period.
4.2 Harsh Climate
Heavy snowfall, low temperatures and a long winter season created a narrow construction time-frame. Low temperatures also influence concrete setting times, grouting efficiency, machinery function and storage of construction materials. Effective temperature control measures were therefore needed for winter construction as well as for mixing plants, processing facilities and tunnel working conditions.
4.3 Complex Surrounding Rock Conditions
Long tunnels through mountains can be subject to fractured rock, weak rock masses, groundwater influx and changing quality of surrounding rock. The support parameters must adapt to the geological conditions that are encountered during excavation. Safe excavation was ensured through a system of interlocking rock reinforcement, support of the exposed surface and advance pre-support.
4.4 Logistics
The remote location of the project site made transportation of staff, machinery and construction material more challenging. Ensuring steady supplies was therefore of great importance, especially since access to the site could be interrupted by adverse weather conditions.
4.5 Seismic Considerations
The tunnel structure was designed for a seismic fortification intensity of Grade VII. Structural stability, continuity of support systems and durability were therefore key design considerations.
5.Ground-Support Requirements
Ground-support in a tunnel of this size and at high-altitude must react quickly to changing ground conditions while providing predictable performance about the excavated profile.
Ground-support systems commonly used on projects such as this include:
5.1 Self-Drilling Rock Bolts
Self-drilling rock bolts allow for drilling, anchoring and grouting in a single operation. Self-drilling rock bolts are especially effective in fractured rock masses and unstable ground conditions where a conventional hole would collapse before the reinforcement element could be placed.
5.2 Hollow Bar Anchors
Grouted hollow bar anchors help reinforce the surrounding groundmass and transfer loadings from weaker rock into stronger, more competent ground. Various lengths, diameters and steel strengths are available to meet required design capacities.
5.3 Fiberglass Rock Bolts
Fiberglass rock bolts are commonly used for temporary reinforcement and tunnel-face stabilization applications. High tensile strengths combined with resistance to corrosion and cuttability make these an excellent choice for areas that may be excavated later.
5.4 Lattice Girders and Steel Support
Lattice girders can be utilized along with shotcrete, mesh, and rock bolts to create a continuous support system about the tunnel profile. This support helps to evenly distribute ground-loading and maintain the designed excavation geometry.
5.5 Pipe Umbrella Pre- Support
Pipe umbrella systems can be used to create a supported canopy in weak, fractured, or shallow cover sections of tunnel ahead of the tunnel face. This support system increases stability within the working area and mitigates excavation-induced deformation.
6. Project Significence
By providing a dependable all-weather route through Xia Gongla Mountain and negating the previous need for vehicles to traverse Xia Gongla Mountain’s snow-prone mountain pass, the Xia Gongla Mountain Tunnel greatly improved transport dependability and safety.
In addition to providing these benefits, the Xia Gongla Mountain Tunnel and the expansion of the G349 highway:
Above all else, this engineering project shows the criticality of long mountain tunnels for crossing high-altitude topographical challenges and constructing dependable routes through undeveloped regions.
7.Wanfeng Tunnel Support Solution
Wanfeng designs and produces ground-support products used in highway tunnels, railway tunnels, mines, hydropower engineering and underground caverns. If you are working on a project with similar conditions to Xia Gongla Mountain Tunnel, we can provide solutions such as:
Product diameter, length, steel material, thread form, corrosion-resistant protection and connection forms can be customized based on geological conditions and project requirements.
Planning to build a highway tunnel or underground project located at high altitude? Reach out to Wanfeng for assistance with product selection, technical papers and customized ground support design solutions.
8.FAQ
8.1 How long is the Xia Gongla Mountain Tunnel?
The main tunnel runs for 4,392 metres. It is a single-bore two-way highway tunnel with a clear width of 9 metres and a clear height of 5 metres.
8.2 Where is Xia Gongla Mountain Tunnel built?
It’s built in Banbar County, Qamdo Region of Tibet Autonomous Region of China. It runs between Tsoka Town and Jinling Township on China National Highway G349.
8.3 Why was Xia Gongla Mountain Tunnel built?
It was constructed to bypass a dangerously steep mountain road that often experienced heavy snow and seasonal road closures. The tunnel allows for safer, faster and reliable transportation all year.
8.4 What are some of the main issues with constructing tunnels at high altitudes?
High-altitude tunnel projects can face issues including low-oxygen environments, low temperatures, heavy snowfall, logistical issues, difficult geology, equipment-performance restrictions, and slow concrete/grout curing.
8.5 What types of ground-support can be used for mountain tunnels?
Self-drilling anchors, hollow bar anchors, fiberglass bolts, friction bolts, lattice girders, shotcrete and pipe umbrella pre-support can all be effective depending on the geological conditions.
