1. 1 road tunnel leakage

In recent years, with the rapid development of highway tunnel construction technology in China, tunnel construction has achieved excellent results, but most tunnels still have different degrees of water leakage, and some tunnels are still quite serious. Tunnel leakage is because the construction of the tunnel destroys the original water balance of the mountain, and the tunnel becomes a channel for groundwater to gather near the mountain. In the engineering survey and design, the engineering geology and hydrogeology were not carefully understood, and the underground water source, water quantity, flow direction and water quality around the lining were not fully investigated; Sometimes there is a lack of indoor experimental data reflecting the performance of waterproof materials and specific requirements for impermeability and corrosion resistance of structures.

1.2 lining crack

The main hazards of lining crack deformation are: (1) reducing the bearing capacity of lining structure to surrounding rock; (2) Reduce the tunnel clearance, encroach on the building clearance, and affect the safe passage of vehicles; (3) The arch lining falls off, which affects traffic and personal safety; (4) Cracks leak, causing corrosion of facilities in the cave and freezing injury in cold areas; (5) Under operating conditions, the cracked lining is overhauled, and the construction and transportation interfere with each other, which increases the cost.

1.3 lining corrosion disease

Compound erosion contains the characteristics of the above two kinds of erosion. Physical corrosion of tunnel lining includes frost heaving damage caused by alternating freezing and thawing and crystal swelling damage caused by alternating dry and wet salt. The strong erosion parts are sulfate crystal erosion parts such as tunnel arch, side wall and side ditch, etc., which ooze water (alternately wet and dry). The seepage points along the cracks are strip-shaped or honeycomb-shaped caves, and mirabilite and gypsum crystals are precipitated, and the structure is further loose, crumbling, bare and falling off.

2. Highway tunnel disease control measures

2. 1 Waterproof and Drainage Technology for Highway Tunnels

The waterproof and drainage system of highway tunnel is designed as a circular structure, which can be summarized as "one wall, two rows and two defenses": a circle of surrounding rock grouting to block water. Between shotcrete and waterproof layer, between waterproof layer and lining, two circles of drainage, waterproof layer and lining concrete waterproof.

2.2 surrounding rock grouting water plugging

Water plugging by surrounding rock grouting can be implemented by drilling holes from the surface before tunnel excavation, or by drilling holes radially or in advance after tunnel excavation. Grouting construction technology of tunnel surrounding rock includes four aspects: selection of grouting materials, grouting slurry, grouting parameters and grouting construction. When selecting grouting materials, the following points should be considered: the slurry has good permeability in compressed rock strata. That is, under a certain pressure, it can penetrate into cracks or cavities with a certain width. After the slurry condenses into stones, it should have certain strength and cohesive force. The number and arrangement of grouting holes directly affect the grouting effect and cost. Hole arrangement should be determined according to equipment capacity, groundwater situation, effective diffusion radius of slurry, rock fracture state, deflection rate and grouting hole density. Through the combination of drawing and calculation, and after repeated comparison. The suitable combination of the length of grouting hole and the length is umbrella-shaped, and its inclination angle varies with the length of grouting section. The specific layout should be adjusted according to the water inflow direction, water seepage and geological conditions. The smaller the crack, the more holes there should be. On the contrary, it can be reduced. Grouting pump pressure is low, so the number of holes should be increased appropriately. Grouting methods include subsection grouting and full-face grouting. The order of subsection grouting is upward and downward. During the construction, the grouting method should be determined according to the water gushing from the borehole, the degree of crack development and the capacity of grouting equipment.

2.3 Drainage between sprayed concrete soil and waterproof layer

At present, there are three laying technologies for waterproofing membrane: hot sealing without nails, cold bonding with nails and multi-point composite laying without nails. Nailless heat sealing laying method. Plastic gaskets and flashing are homogeneous materials. When fixing the flashing, the electric soldering iron heats the flashing and gasket from the surface of the flashing. After heating, the waterproof board is in the molten state first, then the gasket enters the molten state due to heat conduction, and finally the two are fused. Generally, the melting point of gasket is lower than that of waterproof board, which can prevent waterproof board from overheating. Nail cold sticking paving method: when fixing waterproof board, fix plastic gasket with nails first, and the plastic gasket presses waterproof coiled material outside. The bonding between coil gaskets adopts special glue provided by coil manufacturers, which can be used for cold coating construction. Finally, the nail hole is repaired by gluing the coil block slightly larger than the fixed plastic gasket. This technology is characterized by leaving nail marks on the surface of waterproof coiled material, and cold bonding with glue when planting in summer.

2.4 Drainage between waterproof layer and secondary lining

Drainage between waterproof layer and secondary lining is also very important. At present, waterproof and drainage systems in tunnels mostly adopt water-stop belts and drainable rubber water-stop belts. Water-swellable waterstop is a new strip waterproof material made of modified rubber as the main raw material. The modified rubber not only maintains the excellent elasticity, ductility and sealability of the original rubber waterproof products, but also has the characteristic of swelling when it meets water. Drainable water stop is a kind of composite rubber product. Compared with the traditional water stop, it has the structure of bypass, drainage channel, slurry stop filter and flange, which makes it have two functions of water blocking and drainage. The lower part of the water stop must be firmly and smoothly connected with the drain pipe. Only in this way can the water leak smoothly into the drainage hole of the longitudinal drainage pipe. Avoid cutting off the water stop during construction. A working joint and a water stop should avoid overlapping as much as possible to avoid installation defects at the joint.

2.5 lining crack damage and corrosion disease treatment crack repair

Small cracks, no water seepage, can be filled with cement slurry, or gouged first and then plastered with 1: 1 cement mortar or epoxy mortar. In order to prevent the mortar from shrinking after consolidation, 10% ~ 17% micro-expansive agent can be added when preparing mortar. Cracking damage is serious, and there are many cracks in the arch ring, and some of them lose their bearing capacity. In principle, they are demolished and rebuilt. General early strength steel reinforced concrete shotcrete with anchor net or shotcrete. When the cracks are serious, but the basic shape of the arch ring has no great deformation, plain shotcrete or mesh shotcrete can be used for treatment. 2) Grouting the cavity behind the lining. Grouting can fill the gap of arch back (wall back), restrain lining deformation, reinforce and stabilize loose surrounding rock behind lining, fill the gap of lining cracks, and fill the gap of arch back by grouting, which can improve the stress state of lining. Tunnel grouting consumes a lot of cement. In order to save cement consumption, low-priced materials such as cement fly ash mortar, cement zeolite powder mortar and cement clay mortar can be selected, which have good groutability, impermeability and corrosion resistance. 3) subgrade stability treatment. Subgrade is both a force-transmitting structure and a force-bearing structure, and the instability of subgrade directly affects the stability of inverted arch. Weathering and argillaceous rock tunnel has poor drainage at the bottom, and the subgrade is easy to be damaged, resulting in slurry boiling and leakage. Generally, the method of rebuilding and deepening the side ditch or building a deep side ditch is adopted for treatment. Deepen the drainage ditch, discharge groundwater, and eliminate subgrade softening. For soft subgrade.

2.6 Treatment of lining corrosion diseases

The anti-corrosion measures of tunnel lining should start with the survey and design, master the tunnel engineering geological and hydrogeological data, find out the source and composition of corrosive medium in environmental water, and take preventive measures according to local conditions on the basis of correctly judging the corrosion degree of corrosive medium to lining concrete. There are three factors that cause corrosion: ① the existence of corrosive medium; (2) the existence of corrosive substances; ③ Groundwater is active. In view of the causes and conditions of tunnel corrosion, the prevention measures of highway tunnel corrosion mainly include: ① improving the compactness of concrete and the integrity of lining; (2) external mixing feeding method; ③ selecting anti-erosion cement; (4) Strengthen the drainage measures outside the lining; Using dense materials that can't react with concrete to make isolation waterproof layer on the outer surface of lining; ⑤ Using natural stone materials that will not react with corrosive environmental water to build the lining; ⑥ Inject anticorrosive mud behind the lining; ⑦ Use anticorrosive concrete.

3. Conclusion

In a word, the prevention and control of highway tunnel diseases plays a vital role in the operation of the whole highway tunnel. Based on the author's practical experience, this paper summarizes the causes of structural diseases of highway tunnels, and makes a thorough and comprehensive study on prevention and control countermeasures, hoping to provide reference for practical projects.

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