Mapei: Injection Solutions for Underground Construction

Injection can be defined as the introduction of a material with pressure into the ground or a structure for waterproofing and for consolidating voids, cracks and porosity. Generally, the injection can be categorised as Pre Injection and Post Injection.

Pre Injection is cost effective in the following:
  • Water Ingress reduction
  • Ground zones with fractured rocks or weathered rocks
  • Unstable ground
Post Injection is carried out in the following situations:
  • Rehabilitations
  • Structural cracks in concrete
  • Unexpected water ingress
  • Rehabilitation in concrete structures
Pre-Injection depends on Ground Permeability and Water ingress. The objective of carrying out Pre-Injection is to decrease the cost impact of post grouting and decrease the water in tunnel so as to have a smooth excavation. For Pre injections, the packers are placed in sound solid rock to ensure that they are fixed well, and to avoid grout to leak back around the packer. To ensure a successful injection, the packers should be fixed in already injected rock. If not, you will easily get out-leaks through cracks and fissures. Normally, the packers are set 1.5 – 2 meters deep. If packers with non-return valves are used, they should not be mounted before they are ready to be injected. This makes it possible to see if there is contact between the holes.

The packer is attached to the injection pipes and pushed into the drilled hole. The innermost of the two injection pipes has a tightening lever for fixing the packer. The packer is expanded in the drilled hole using the tightening lever. Cement mixture or chemical substance is injected into the rock’s crack system through the rubber valve in the packer.

Injection Solutions
Mapei provides different products for injections for pre-grouting
  • Microfine Cement MICROCEM 8000
  • Ultrafine Cement MICROCEM 12000
Microfine cement and Ultrafine cement blaine value varies from 6000 to 12000 compared to cement which is around 3500 cm2/g. Wherever the finer penetration is required, the blaine value plays an important role. For pre-grouting, various important features have to be considered. These include:
  • Bleeding
  • Desired fluidity
  • Setting time / gelling time
  • Strength required
Bleeding has to be less than 2% and fluidity when tested in Marsh cone should be 35 second. Fluidity plays an important role in injections. If fluidity has to be higher, then a grout has to balance between fluidity and bleeding. Lower the water cement ratio fluidity decreases, to balance it we can add viscosity fluidifier with a dosage that is is 2-6% by weight of cement. To accelerate the setting time, an accelerator can be added. The mechanical strength in 24 hours vary from 2 Mpa to 20 Mpa depending on the water cement ratio varying from 0.7 to 1.00

Filtration Ability Against Pressure

The coefficient of filtration ability against pressure shows the ability of the fluid to keep the initial characteristics even in the presence of pressure.

Injection Solution

In case of heavy ingress of water, it’s better to go for a fast setting injection of resins. Generally, polyurethanes like RESFOAM 1KM or FOAMJET are better. Double component are faster in setting whereas the time of setting of Single component can be controlled if it has to be injected for a longer distance with an accelerator. Also, Nano Silica based injection material is used; it generally has particle sizes of less than 0.1 micron like the Mapejetsystem NS15.

Colloidal silica gel is a “mineral grout” and not a chemical grout It is a stable liquid containing single, sub-microscopic particles of silica oxide. To make it gel, a weak solution of salt water is mixed prior to pumping. The more salt water added, the faster the gel time. It is environmentally friendly and durable, as it is simply composed of quartz sand, water and salt. Having the consistency of water, it penetrates sands and fine fissures very easily. It is extremely user-friendly as a standard cement grout equipment can be used and cleaned with water.

In Grouting the most important is the GIN (Grout Intensity Number). GIN grouting intensity values were defined as the product of the final grouting pressure and absorption per meter for a given single borehole, within a certain period at the end of grouting the result is a constant value.


where P is the final grouting pressure and V is the ultimate grout take which means the energy consumption per unit grouting period
  • Alluvial Soil Grout pressure: low, average 2-4 bar, maximum 7-10 bar
  • Cracks in Rock Grout pressure: High, average 30-40 bar, maximum 70-80 bar
GIN value varies with different geological conditions, but GIN is constant under similar conditions. It needs to be noted that the GIN in each envelope curve includes a maximum pressure and maximum absorption slurry in addition to a GIN value. When the injection rate reaches a pre-determined limit, or pressure reaches the limit, or the product of the two factors achieve the selected GIN, the grouting can be ended.

Post Injection: Basic features

Reactive mindset: post-injection is conducted when collapses have occured already or uncontorolled water inflow is occuring; or where rehabilitation of leaking tunnels is required; or drilling holes to intersect joints with high water inflow, or pushing slotted pipes into unstable ground masses. These may need specialised drilling equipment such as Odex, Self drilling anchors and packer injections, utilization of expensive, highly reactive chemicals - usually PUs in geotechnical problems and acrylates in rehabilitation problems.

Injections Solution

Single Component Polyurethane or Double Component Polyurethanes can be used, or Acrylates. To stop water ingress immediately the Polyurethane can be injected and then acrylates can be injected into joints or cracks. Various Tunnel linings have used the leakage control method with Polyurethanes like RESFOAM / FOAMJET and Mapegel UTT.

Injection in fissures:
  • Extremely low viscosity
  • Resin should also be injectable when gelling has commenced
  • Gelling properties, accurately adjustable
Technical solution for rehabilitation of old tunnels
  • Acrylates for the injections in and immediately behind deteriorated concrete lining
  • Polyurethane (Resfoam 1km) for the improvement of ground, void filling and water seepage reduction
  • Taylored cement-based grout for improvement of ground behind concrete and masonry lining
  • Sprayable waterproofing membrane on old tunnel lining
  • Eventual sprayed concrete
Injections Solution Table1

Grouting is a design choice: Pre-injection vs Post Injection

Pre-injection – proactive, relies on effective probing and decision making at the face, cheap materials, 10 to 50 times then post, pre-injection often difficult in soft ground tunneling.

Sanjay BhallaSanjay Bhalla, CEO, Mapei Construction Products India
Post-injection – reactive, the last resort, expensive chemicals, unstable conditions and uncontrollable water inflows.

Make the right choice of materials for the right situation at the design stage and tender for it.

Cannot rely on contractors to price for the unforeseen, provisional sums in contracts required giving contractor all available tools necessary to do the job straight away.

Mapei India provides a complete system of Pre Injection and Post Injection for Civil Engineering Projects.

NBM&CW May 2019

Click Here
To Know More / Contact The Manufacturer
Please fill in your details, we will contact you as soon as possible
Choose Title from the listPlease let us know your name.
Please let us know your Designation.
Invalid Input
Please let us know your email address.
Please let us know your City.
Please let us know your Contact Number.
Please brief your query.
Our other value-added services:

To receive updates through e-mail on Products, New Technologies & Equipment, please select the Product Category(s) you are interested in and click 'Submit'. This will help you save time plus you will get the best price quotations from many manufacturers, which you can then evaluate and negotiate.

Equipment & Machinery
Invalid Input
Building Products
Invalid Input

Open-type TBM produced by CRCHI creates a new record in China

Being the longest water delivery line in the history of Jilin province, transferring water from Songhua River into Central Jilin Province will transfer the largest capacity of water and cover the largest areas. The water diversion Read More ...

Composite Shell Lining for Tunnels and Mined Stations

Amit Kaul, BASF India Limited (Construction Chemicals Division), India, tells about the innovative tunnel lining system and related design aspects, and also describes the main advantages of this lining system in comparison Read More ...

Impact of Underground Construction n Urban-Built Environments

Underground infrastructures are an integral part of modern cities as they serve to counter problems of surface congestion and environmental degradation. The problems of ground vibrations, vibration induced noise and ground Read More ...

The Largest Diameter TBM in India Made by CRCHI will be used in Mumbai Coastal Road Project

On March 18, 2020, India’s largest diameter TBM was packed at CRCHI’s first industrial park in the Changsha city, central-south of China. It will pass through Shanghai Port to Mumbai for a costal road project. With an excavation Read More ...

CREG Φ15.8m Slurry TBM Solution for Chunfeng Tunnel in Shenzhen

Chunfeng Tunnel is the first bi-directional four-lane highway tunnel in Shenzhen, China, with two decks within one tunnel. The tunnel is 3,603m long; its average radius of curve is R750m and its biggest gradient reaches 49% Read More ...

CRCHI TBMs used in Under River Tunnel Project of Yuan River in Changde in Hunan Province, China, for customer CRCC 14th Bureau Group

The under-river tunnel project of Yuan River in Changde is a twin-tube tunnel in the Chinese inland city of Changde. The tunnel connects two sides of the Yuan River, and with its two-way and four-lane, it will promote harmonious Read More ...

GHH’s MK-A35 – Ideal for Tunneling & Mass Mining

With the 2020 upgrade of its long-proven MK-A35 model, GHH, German manufacturer of heavy machinery for mining, tunneling, and special civil engineering, presents the first 35-ton class dump truck, already operating in the field Read More ...

Srons Engineers, India’s first company to manufacture SDA Bars, has a strong quality control policy in place

Established in 2015 to support the growing demand of its Rock Hardware products, Srons Engineers is an Indian manufacturer of Rock Bolts, Self-drilling Anchor systems and Self Drilling Anchor Bolt parts like hollow bar & rod Read More ...

Tunneling, Rock Support & Geotechnical Solutions by MIPL & ROBIT

Machino International (MIPL) - a specialist company based in New Delhi, is a leading supplier of Construction, Tunnelling and Geotechnical products. The company has more than 30 years of experience in H.E.P, Road Tunnels, Cavern projects Read More ...

Turkey’s Tough Geology Inspires Robust Machine Design

Driven through a mountain side with 600-m of cover in Central Turkey, the Kargi Kizilirmak Hydroelectric Project is one of the most challenging tunneling projects ever completed in the region. The project is located on the Kızılırmak River Read More ...

CREG’s EPB TBM Ready to Perform in Italy

The Turin-Venice high-speed rail is part of the Pan-European Multimodal Corridor, which traverses the northern part of Italy and connects the northwest to the northeast of the country. It is an important gateway for Western European countries Read More ...

Characteristics & Categorization of Tunnel Fires & Their Mitigation

A fire that develops in a tunnel interacts with the ventilation airflow and generates complicated air flow patterns and turbulence in the vicinity. The heat generated warms up the surrounding air, and in case of a slope inside Read More ...

Tunnel Renovation Redefined

During renovation of the Hasselborner Tunnel in Central Hesse, Germany, contractor Baresel used a method they hadn't tried before. Parts of the tunnel lining had to be removed and the areas were subsequently Read More ...

GHH adds Shotcreting Machine to its - Tunneling Equipment Solutions

GHH is offering state-of-the-art and proven IS26 Concrete Spraying (Shotcrete) machine in India. The machine is suitable for shotcreting application in medium and large sized tunnels with cross sections ranging Read More ...

Kishanganga Hydro Power project – A New Power House

Inaugurated by the Prime Minister of India, the Kishanganga Hydro Electric Power project is the first mega hydro power plant to be awarded as EPC to HCC by NHPC. Located at Bandipore in north Kashmir, the Read More ...

Tunneling to Prosperity: Solutions, Equipment and Technologies

India is one of the fastest growing markets for tunnel construction due to various infrastructure development projects underway across the country. Tunnels are required for hydroelectric power projects, for improving road Read More ...

New Building Material & Construction World

New Building Material & Construction World
MGS Architecture

Modern Green Structures & Architecture

Modern Green Structures & Architecture

Lifting & Specialized Transport

Lifting & Specialized Transport

Indian Infrastructure & Tenders Week

Indian Infrastructure & Tenders Week