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 provide your details we will contact you as soon as possible
Please let us know your name.
Invalid Input
Please let us know your Designation.
Invalid Input
Please let us know your City.
Please let us know your State.
Please let us know your Country.
Please let us know your Contact Number.
Please let us know your email address.
Please brief your query.

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 ...

CREG: Tunneling Specialist

China-based China Railway Engineering Equipment Group Co., Ltd (CREG) is a subsidiary of the public- listed China Railway Engineering Corporation (CREC), a Fortune 500 company and a key state-owned company under Read More ...

Intermodality & Last Mile Connectivity - Creating Smart Walkable Spaces

Urban congestion needs to be addressed by encouraging high quality and innovative energy-efficient public transport integrating it with other forms of paratransit, ensuring last mile connectivity; working on Read More ...

Ashram Metro Station - An Engineering Masterpiece

One of the main challenges of constructing a station in the Delhi Metro Network, especially in a busy and densely populated area, is designing it according to the ambience and the limited space allocated. Constructing Read More ...

Transit Oriented Development - Challenges and Proposed Regulatory Framework

Transit Oriented Development (TOD) complements the concept of new urbanism. Compact, mixed-use communities are the answer to suburban problems. Due to the dynamic nature and multiplicity of underlying Read More ...

Simulating oversize and heavy vehicle manoeuvres using AutoTURN® from Transoft Solutions.

Use AutoTURN® to design infrastructure adjustments to safely operate trucks transporting wind turbine components. By Er. Alessio Gori - collaborator at POLITECNICA INGEGNERIA ED ARCHITETTURA SOC. COOP. Read More ...

Urgent Course Correction Imperative for Indian Railways

Railways’ freight and passenger businesses over the 5-year period, i.e., 2014-15 to 2018-19 (budgeted) indicate a flat growth. The number of total passenger journeys would record a CAGR of 0.22%, passenger kilometres Read More ...

Meeting Emerging Urban Transport Challenges

The Ministry of Housing and Urban Affairs has envisaged growth of urban transport along with a low carbon footprint through seamless implementation of a New Metro Rail Policy, announced last year Read More ...

Tunnelling Through the Ages

History has seen the evolution of tunnelling starting with cave formation, for water management, underground transportation, mineral extraction and for warfare purposes. The oldest reference of a tunnel was Read More ...

Afcons uses Robbins EPB TBM to Complete Third Bore for Chennai Metro Project

Contractor Afcons Infrastructure Ltd used a 6.65 m (21.8 ft) diameter Robbins EPB TBM to bore through in Chennai Metro, making it the contractor's third tunnel to be bored by the machine for the project. The three Read More ...

Robbins Slurry TBM ramps up for Mumbai Metro Line 3

The first of two Slurry TBMs, a rebuilt 6.65 m (21.8 ft) diameter machine, passed its factory acceptance on September 4, 2017 in Singapore. The machine, fitted with a Robbins cutterhead and outer Read More ...

Tunnelling Technologies & product support keep pace with construction complexities

Advanced technologies, mechani- sation of equipment with heightened safety features, and timely service and technical support to end-users can help the construction industry deal with construction complexities 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