FIELD OF THE INVENTION
The present invention relates to a method for seepage control in tunnel. More particularly, the invention relates to a method to control seepage in a tunnel using chemical grouting to arrest water ingress inside the tunnel.

BACKGROUND OF THE INVENTION
Tunnels are essential civil structures that are dug in soil, earth and rocks to create passageways where there is hindrance due to mountain ranges between two places or shorten distances between two places. Tunnels are used for foot or vehicular travel and at times they are dedicated for railway lines. Tunnels depending on the cross-section may be shaped as round, semicircular, rectangular, elliptical and segmental shape.
While construction of tunnels, the soil undergoes a lot of boring and drilling which consequently disturbs the soil structure and natural water channels present in the soil. Such disturbances to natural water channels may cause water seepage in the tunnels if adequate precautions are not taken while construction of tunnel. Also, at times the soil near tunnels experiences erosion in long run due to encroachment of land. Rainy season in addition contributor to this soil erosion due to creation of troughs and cracks in the soil and causes water seepage in tunnels. The water ingress results into development of cracks and bulging in the tunnels also. The tunnels with inside brick lining gives rise to distress due to such seepage.
Conventionally, in order to stop seepage a lot of seepage controlling methods are used such as seepage control lining made from concrete, reinforced concrete slabs, asphalt, rock, clay; creating seepage control barriers using polymers and grouting using cement etc. But, the durability of such methods is highly dependent on the kind of soil where such seepage control methods are applied. There is also possibility of weathering of rock mass during due to chemical reaction with water. Further, the most common method used is cement grouting which only provides temporary solution and gets washed away soon due to heavy rains or water clogging. Hence, cement grouts do not provide a permanent solution to the seepage and are inadequate in controlling the seepage.
Therefore, there is a need of technology and methodology to overcome above mentioned shortcomings and provide a seepage control method that provides longevity to the existing tunnels without any constraint of soil where the seepage control technique is applied. Further, there is need of seepage control technology that offers seepage control to a tunnel while its construction as well as existing structures.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a method for seepage control of a tunnel during its construction as well as existing structures using chemical grouts.
Yet another object of the present invention is to provide a seepage control method to prevent soil erosion surrounding tunnel during rainy seasons and preventing water seepages inside the tunnel.
Yet another object of the present invention is to provide a sealing technology for fissures and fine cracks in fractured rocks or concrete and an existing structure to control water seepage.
Yet another object of the present invention is to provide a grouting technology that enables injection of grout precisely at desired locations.
Still another object of the present invention is to provide a grout technology using chemical grout with that provides impermeabilization of the strata with high efficiency and increase the life of structure.

SUMMARY OF THE INVENTION
In an embodiment of the present invention an effective and time saving method for seepage control of a tunnel with help of a chemical grouting in fan pattern that is capable of controlling high water movements and being able to seal fine fissures and cracks in the tunnel and increase the life of the tunnel.
In another embodiment of the present invention, method of seepage control of a round tunnel comprises the steps of: drilling holes to create a grout curtain for grouting; injecting grout under a grouting injection pressure; and drilling drainage holes below spring level to provide a passage to ground water diverted by grouted rock mass. The grout used is a resin that is capable of arresting water ingress in the tunnel and injected through perforated self drilling anchor bars to allow the injection of grout in fine cracks and fissures of rock mass. The chemical grout used hardens with or without water and create a waterproof sheath of variable thickness with a PU foam mantle that permanently consolidates the surrounding land or rock.
Therefore, the method for seepage control for a round tunnel efficiently addresses the issues of water seepage inside the tunnel and erosion of soil during rainy seasons etc. regardless of the type of soil where this method is applied. The technique is useful in increasing the strength of the tunnel and providing impermeabilization of the surrounding strata.

BRIEF DESCRIPTION OF THE DRAWING
An understanding of the system and method of the present invention may be obtained by reference to the following drawings:
Figure 1 depicts a cross sectional view of the drilling plan in accordance with an embodiment of the present invention.
Figure 2 shows longitudinal section of the grouting holes in a tunnel in accordance with an embodiment of the present invention.
Figure 3a and Figure 3b shows views of an intermediate stage in the process of grouting in accordance with an embodiment of the present invention.
Figure 4a and Figure 4b illustrates views of the final stage in the process of grouting in accordance with an embodiment of the present invention.

DESCRIPTION OF THE INVENTION
The present invention will now be described hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.
In a preferred embodiment of the present invention, a method of seepage control for a round tunnel is provided to prevent problems water seepage due to heavy rains, water clogging and erosion of soil etc. Therefore, a method of seepage control for a tunnel comprising of:
a) drilling a plurality of holes of a predetermined length in a predefined pattern on wall of tunnel having a predefined longitudinal spacing and inclined to an angle with respect to the longitudinal axis of the tunnel to create a grout curtain;

b) injecting a chemical grout in the drilling holes as obtained in step a) under a predetermined grouting injection pressure to reach a predefined length;

c) allowing said chemical grout injected in step b) to settle down for a predefined time duration;

d) drilling a plurality of drainage holes of predefined length below spring level on each side of tunnel; and

e) fitting the drainage holes obtained in step d) with PVC pipes wrapped with geotextiles to provide a passage to ground water diverted by grouted rock mass.

The predefined pattern for drilling holes is a staggered pattern with holes drilled at a spacing of minimum 0.25 m c/c to maximum as per geological condition of site of tunnel. Further, the predefined longitudinal spacing in the holes is at least 0.25 m and the holes are inclined to an angle in the range of 30° to 90° to the longitudinal tunnel axis to get a grouted zone around the tunnel periphery. The dimensions of grouted zone depend on the dimensions of drilling holes and angle of its inclination. The predetermined length of the holes is minimum 0.3 m to a maximum as per geological condition of site of tunnel. The predetermined grouting injection pressure is determined based on geological condition of site of tunnel and the predefined length to which the grout must reach is preferably a minimum 0.1 m to maximum as per geological condition of site of tunnel radially. The predefined time duration for the chemical grout to settle down is in the range of 5 seconds to 30 minutes. The predefined length of drainage hole is in the range of 1 m to maximum limit as per condition of site of tunnel.

In an embodiment a tunnel with brick lining where the seepage control method is to be applied is monitored for signs of distressing and deformation. Deformation measurements are carried out using optical targets located on the brick lining at crown and near the spring level measured with surveying equipment. The spring level is horizontal reference line where vertical sidewalls meet the arch of round tunnel.

Figure 1 depicts a cross sectional view of the drilling plan of the round tunnel. The drilling holes (1) are drilled on wall (5) of tunnel to a predefined length which is 5 m based on the site conditions and are spaced at 2.2 m c/c. Also, the drilling holes (1) are inclined to an angle in the range of 40° to 45° to the tunnel axis based on the geological conditions of the site of tunnel to get a grouted zone of approximately 3m around the tunnel periphery forming a fan pattern with respect to the tunnel profile. Self drilling anchors are used for drilling and grouting and provide path for the flow of grout for reinforcing the rock mass around the tunnel which gets weakened due to cracks and water flow inside. The self drilling anchors are perforated for providing path to chemical grout for flow. The wall (5) of the tunnel is made using construction materials including but not limited to bricks.

Further, drainage holes (2) are drilled below spring level on each side of the tunnel periphery of a length in the range of 5 m to 10 m depending on the site conditions. These drainage holes (2) are then fitted with perforated PVC pipes wrapped with geotextiles to provide passage to ground water diverted by the grouted rock mass. The drained water gets collected in the tunnel drainage through flexible PVC pipes and transported out of the tunnel. These drainage holes (2) help in reducing hydrostatic pressure built up due to water head above the tunnel.
Figure 2 shows longitudinal section of the grouting holes in a tunnel. Here, in a section/ring of grout curtain, the holes (1) are drilled at a spacing of 2.2 m c/c in a staggered pattern. The holes (1) are spread from the spring level (3) to the crown (4). The staggered pattern of the holes (1) inclined at an angle of 40° to 45° based on site conditions shall be drilled with longitudinal spacing of 1.1 m to get a grouted zone of approximately 3 m around the tunnel periphery.
Figure 3a and Figure 3b indicates two views of an intermediate stage in the process of grouting. In the intermediate stage, the grout is injected under a predetermined grouting pressure in the grout hole and it starts filling in the open joints and fissures in the soil and rock mass.
Figure 4a and Figure 4b elucidates two views of the final stage in the process of grouting. In the final stage, the grout has completely filled the open joints and fissures. The distance up to which the grout reaches is proportional to the grouting pressure and this distance is such that overlap maximum area is grouted. The maximum grouting pressure is measured based on site conditions and checked against local conditions in the tunnel. Poor rock condition in the tunnel, high hydrostatic pressure and backflow are indicators of maximum grouting pressure.
The chemical grout used is preferably a two component chemical grout that penetrates in radial direction and into the joint rock mass. It penetrates into the tiniest of fissures and seals them against water infiltration. The first contact with water causes the resin to expand into stable, compact foam and the fast reaction speed quickly blocks water infiltration. Further when the chemical grout reacts in absence of humidity it forms a compact, flexible and resistant resin without any increase in volume and pushing the porous material into the base thereby forming a waterproof sheath of variable thickness surrounded by a PU foam mantle that permanently consolidates the surrounding land or rock.
Therefore, the present invention provides a seepage control method for tunnel regardless of soil conditions around the soil using a chemical grout that penetrates into the tiniest of fissures and seals them against water infiltration and forms a waterproof sheath that permanently consolidates the surrounding land or rock. The present invention therefore provides protection against collapse of soil/ground due to rains and water clogging.
Many modifications and other embodiments of the invention set forth herein will readily occur to one skilled in the art to which the invention pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

We claim:
1. A method of seepage control for a tunnel comprising the steps:

a) drilling a plurality of drilling holes of a predetermined length in a predefined pattern on wall of tunnel having a predefined longitudinal spacing and inclined to an angle with respect to the longitudinal axis of the tunnel to create a grout curtain;

b) injecting a chemical grout in the drilling holes as obtained in step a) under a predetermined grouting injection pressure to reach a predefined length;

c) allowing said chemical grout injected in step b) to settle down for a predefined time duration;

d) drilling a plurality of drainage holes of predefined length below spring level on each side of tunnel; and

e) fitting the drainage holes obtained in step d) with PVC pipes wrapped with geotextiles to provide a passage to ground water diverted by grouted rock mass.

2. The method as claimed in claim 1, wherein the predetermined length of holes is minimum 0.3 m to maximum as per geological condition of site of tunnel.

3. The method as claimed in claim 1, wherein the predefined pattern for drilling holes is a staggered pattern with holes drilled at a spacing of minimum 0.25 m c/c to maximum as per geological condition of site of tunnel.
4. The method as claimed in claim 1, wherein the predefined longitudinal spacing in the drilling holes is at least 0.25 m and the holes are inclined to an angle in the range of 30° to 90° with respect to the longitudinal axis of the tunnel.

5. The method as claimed in claim 1, wherein the predetermined grouting injection pressure is determined based on geological condition of site of tunnel and the predefined length to which the grout must reach is preferably minimum 0.1 m to maximum as per geological condition of site of tunnel radially.

6. The method as claimed in claim 1, wherein the predefined time duration for the chemical grout to settle down is in the range of 5 seconds to 30 minutes.

7. The method as claimed in claim 1, wherein the predefined length of drainage hole is in the range of 1 m to maximum limit as per condition of site of tunnel.

8. The method as claimed in claim 1, wherein the chemical grout is a two component chemical grout in form of resin that on first contact with water causes the resin to expand into a stable, compact foam to block water infiltration and then in absence of humidity a compact, flexible and resistant resin is formed.

9. The method as claimed in claim 1, wherein the chemical grout forms a waterproof sheath of variable thickness surrounded by a PU foam mantle that consolidates the surrounding land or rock.

10. The method as claimed in claim 1, wherein the drilling and grouting is done using perforated self drilling anchors.