Tunnel lining with

geomembrane sheet

Currently, the problem of water leakage in tunnel lining is more serious, especially in weak joints such as construction joints, tunnel joints and joints between pipe joints. How to do a good job in tunnel waterproofing and drainage design and crack waterproof technology is an important condition to ensure driving safety and whether the tunnel can be used for a long time or not.

Improved waterproofing and drainage before entering the hole in the tunnel lining
First, before the water enters the tunnel, the surface water should be checked in the area of ​​the tunnel axis, the method of filling and surface water source should be analyzed, and the surface water and drainage work should be done well.

and exploratory pits with layered and compact clay; For valleys that pass above the tunnel and have many cracks in the rock formation at the bottom, it is recommended to pave the bottom of the pit with crushed stone, and if necessary, use cement mortar to plaster the surface; Dig a closed water trough near the tunnel to prevent water accumulation; There are springs on the surface, where the gushing water is located, a conduit is buried to drain the spring water.

A chute is constructed at the top of the tunnel opening based on the design requirements, and a rubble masonry is constructed to drain surface water outside the surface through which the tunnel passes to prevent surface water infiltration and leakage.

The entrance of the tunnel should be washed and connected to the side ditch of the road bed to form a drainage system; Excavated slopes and side slopes at the top of the tunnel can be sealed with shotcrete and nets should be hung at the top of the tunnel. entrance and on both sides. When the high-pressure pool is placed on top of the cave, anti-leakage and overflow facilities should be well prepared and the pool should be placed away from the tunnel axis.

Waterproofing operation and drainage of water eruption areas during excavation in tunnel lining

(1) The principles of waterproofing and drainage treatment for water gushing areas. In the process of tunnel construction, water gushing on the excavation surface should be investigated and analyzed, its cause identified, and the comprehensive improvement principle of “mainly drainage, combined with prevention, drainage, interception and blocking” should be adopted.

And treatment plans should be developed according to local conditions to achieve the goal of unobstructed drainage, reliable waterproofing, economical and problem-free in the future.

(2) Analysis of the causes of the flood zone in the tunnel lining. The phenomenon of water gushing in tunnels is generally due to the development of underground water and the local gushing of water from the tunnel wall; When hitting the fault zone, the rock is broken, a crack is created and water gushes out;

The upper cover of the tunnel is thin, rock cracks are formed, and surface water penetrates into the excavation and other reasons. During construction, the place of water exit, water volume, water inlet, change law, supply source and water quality components in the cave should be observed and recorded, and waterproofing and drainage measures should be continuously improved.

(3) The treatment method of the flooded area. For sections with high inflow water or underground water level in the cave, auxiliary construction such as advanced excavation drainage, auxiliary tunnel drainage, advanced small pipe water blocking, water blocking before injection of surrounding rock, well point dewatering and deep well. Dehydration can be used.

When the water flow is concentrated, a perforated or slotted friction screw can be used for drainage before the injection anchor; When the area of ​​water intrusion is large, a soft dendritic permeable tube can be placed on the surrounding rock surface before injection. An anchor to divert the flow of water, and then spray concrete; When the water flow is serious, a basin hole can be created on the surrounding rock surface and the water can be sprayed during discharge.

Purification and control of waterproofing and drainage in the secondary lining in the tunnel lining

(1) Installation and control of geomembrane waterproof layer in tunnel lining

When entering the site, check the waterproofing layer of the geomembrane. In addition to sampling and inspecting the surface of the waterproof geomembrane according to the necessary work procedures, it should also be checked for discoloration, wrinkles (uneven thickness), stains, tears, knife marks, small holes, and other defects. Qualitative , they must be dealt with in time.

Inspection and improvement of primary support before laying waterproof geomembrane layer in tunnel lining. Before laying the waterproof geomembrane layer, the initial support shotcrete should be measured, the under-excavated parts should be shaved, and the concave and convex parts of the shotcrete surface should be leveled by layer spraying. The screw head and the exposed steel mesh should be cut at the same root and smoothed with cement mortar to make the concrete surface smooth.

Inspect and maintain the waterproof geomembrane layer after installation. After finishing the installation of the waterproof geomembrane layer in the tunnel lining, the supervising engineer must check the welding quality and the layering quality of the waterproof layer. The inspection methods are as follows:

(1) Hold up the waterproof geomembrane with your hand to see if it can be closely attached to the shotcrete.

(2) Check whether the surface of the waterproof geomembrane is scratched, torn or punctured.

(3) check whether the width of the weld or joint (when welding, the width of the lap is 10 cm, the width of the weld on both sides should not be less than 2.5 cm; when joint, the width of the lap is 10 cm, and the width of the joint should be less than 5 cm) whether it meets the requirements, and whether there is welding leakage, false welding, burning and other phenomena.

(4) Are the exposed anchor points (nails) of the arch and the arch wall covered with plastic sheets.

(5) For each sheet 20-30 meters wide, cut 2-3 welds, 0.5 meters each. See if there is false welding or no welding.

(6) Carry out pressurized water (air) test to see if there is water (air) leakage phenomenon etc.

And check the quality of waterproof geomembranes. If any problem is observed, in addition to the detailed records, the construction unit should be immediately informed for repair and those who failed to do the work, should be firmly obliged to do the work again.

Tunnel lining with geomembrane

(2) Installation and control of waterstop in tunnel lining

Waterproof concrete construction joints are caused by covering the waterproof concrete gap filling structure. For waterproofing and drainage of construction joints, plastic waterproofs or rubber waterproofs are generally used in composite liners.
Inspection and improvement of the end of the secondary cover. Before pouring the secondary cover concrete, use a wire brush to brush off the upper concrete piles, or within 4 hours to 12 hours after pouring the lining concrete, wash the concrete surface with high-pressure water and check that the waterstop joints are in good condition.

Are they good or not? Check if the concrete is punctured during the pouring process, and if the waterstop is offset. If any cuts, cracks, loose connections and deviations are observed, repair and treatment should be done in time to ensure the waterproof performance of Waterstop.

Inspection and improvement of waterstop installation quality. Check whether there are auxiliary devices to stabilize the waterstop and prevent deviation, whether the width of the waterstop connection meets the requirements, whether the waterstop is cut or broken, whether the waterstop is fixed by a tight ring and at both ends to Extruded inside the concrete or not. etc., record detailed inspection records.

If there is a problem, the building unit should be notified immediately to carry out repairs, and those who failed should be re-requested decisively.

(3) Pouring and control of concrete in tunnel lining

During the construction of lining concrete, the construction unit should be encouraged to strengthen the management of commercial concrete back stock and conduct regular and irregular inspections. When concrete vibrates, a special person should be responsible to avoid the phenomena of vibration, leakage vibration and excessive vibration.

Vibrating Concrete Strengthen weak bonds such as construction joints and deformation joints, eliminate air bubbles and voids in the bottom of the waterstop, and firmly bond the waterstop and concrete together.

Improvement and control of secondary coating leakage in tunnel lining

(1) Drainage and blocking in tunnel lining. For leaks and cracks, you can use the chisel and plug drainage method. For example, a groove with a certain width and depth (such as 20 mm wide and 30 mm deep) is removed from the cover concrete along the direction of the crack at the leakage site and a semicircular rubber hose with a slightly larger diameter.

From the width of the groove or the width of the groove to introduce water to the side wall in the drainage pit, cover the semi-circular rubber hose with non-woven fabric or seal with anti-leakage material and then seal. Or plaster the surface with waterproof concrete of the same color.

(2) Injection of slurry in the tunnel lining. For serious leaky parts, the method of making grout can be used. For example, dig a hole with a certain width and depth (such as 80 mm diameter and 40 mm) at the leakage site, clean the concrete slag, and check the compaction of the surface concrete. Make holes from the place of leakage. It is recommended to control the thickness of the lining and its depth. After the grouting is finished, the pits can be waterproofed and connected according to method 4.1 above.

Conclusion

The construction quality of any process is greatly affected by the waterproofing and drainage of the tunnel, and any negligence in the construction may bring hidden risks of water leakage.

Therefore, the construction quality control of each process should be strengthened, and the construction should be carried out in accordance with the specifications to ensure that the construction achieves the design effect, so that the quality of tunnel waterproofing and drainage is guaranteed. Arin Khak company is ready to cooperate with you dear ones in the field of tunnel lining with geomembrane sheets. Contact our team for free consultation.