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Tunnels: the problem of groundwater inflows and water seepage
We are heading towards summer and finally, after two years of the pandemic, people will be making a mass exodus to tourist resorts again. Those who choose the mountains (or the sea, for example, the Ligurian Riviera) will find themselves passing through more than one tunnel.
Italy is one of the countries in Europe with the largest number of road tunnels. As for the TERN (TRANS-EUROPEAN ROAD NETWORK), there are currently about 610 road tunnels in operation covering a total length of about 710 km. The total number of tunnels in operation on ANAS (National Autonomous Roads Corporation) roads is 1,235 km, covering a total length of approximately 755 km.
Especially in older tunnels, you may notice large damp patches running high up the inside walls, or dangerous water stagnation on the ground. So, let’s see what exactly happens and how to prevent the problem.
When building tunnels today, tried and tested systems and materials exist. However, the problem that still needs to be addressed is the hydro-geological aspect, which highlights two main problems: groundwater inflows and water seepage.
By groundwater inflows, we mean the sudden flow of water from walls, coming from an aquifer that finds a new outlet. So, after detecting it, it becomes a priority to plan adequate drainage methods.
Water seepage, instead, refers to the passage of water due to its inherent capillary action or to the force of gravity.
The consequences of groundwater inflows and water seepage can be seen if problems are not tackled, or rather prevented, correctly.
Water is a major threat to structures such as tunnels, since it reduces the life of concrete cladding, causing structural deterioration, endangering systems and posing a hazard to road safety.
What can be done about water?
The ideal solution is to design with suitable drainage systems, with studded membranes and drainage geocomposites.
Maxistud and HDD by TeMa Geo Solutions are HDPE studded membranes with high compressive strength: the former is a 20 mm thermoformed membrane, whereas the latter is a 10 mm membrane bonded to a non-woven geotextile, available in different weights and increasing compressive strengths.
Drainage geocomposites such as Q-Drain ZW5 60 20P TG, 5mm thick with a monofilament core, and a nonwoven fabric can also be used.
The choice of product and the thickness depends on conditions regarding groundwater inflow and the relative risk of water seepage.
Controlled landfills and the importance of isolating them
Landfills for inert, non-hazardous and hazardous waste are governed by specific laws in each country, which set out precise regulations on the construction and maintenance of these sites.
As they are virtually in the ground and designed for certain types of waste, they must meet environmental and safety standards.
Let’s take a look at everything in detail.
The risks of not isolating them
Assuming that proper disposal is essential, many types of waste can take years, even decades, to disintegrate and complete natural decomposition processes. At this stage, they produce a large amount of slurry, such as leachate, which is extremely contaminating for the soil and for groundwater.
Moreover, biogases are also produced, mainly methane and carbon dioxide, due to the breakdown of organic material, which must be controlled and could be used to produce renewable energy.
How to isolate them
Controlled landfills need to be isolated from the ground that hosts them, but to be safe they need to fulfil different functions.
Surface erosion control
Vegetation naturally protects the ground from erosion by weather conditions such as wind and rain, which would cause subsidence. While waiting for grassing to protect the sides and surface of the landfill, anti-erosion geomats, in a biodegradable and synthetic version, can be chosen according to needs.
TeMa Geo Solutions offers a wide range to choose from, which can be browsed here.
Reinforcement
A landfill site is sometimes designed and built on more or less steep slopes. If a slope is steep and the ground is unable to support itself, retaining grids need to be installed in order to prevent slippage, which would expose and damage lower layers. View all our solutions.
Drainage
Specific products, drainage geocomposites, can be used for the drainage of rainwater and leachate, which inevitably builds up and must be kept away from the ground.
Barrier
Bentonite-based products, such as Barrier Bento, allow the area to be waterproofed, including walls with high slopes and the bottom.
Capping
Landfills also have a final cover that must meet precise criteria. These include isolating waste from the ground and surface erosion control. However, minimising water seepage and blending into the landscape are equally important.
New solutions in road construction and/or repairs
The safety of road infrastructures is the main goal, and maintenance work – whether preventive or supplementary – is systematic.
Road surfaces withstand heavy traffic loads and atmospheric changes with significant variations in temperature. Constant maintenance is therefore required in order to ensure even surfaces and the stability of structural elements.
Let’s look at the main factors involved in building new roads or maintaining roads.
Controlling surface erosion
Erosion is largely due to freeze/thaw cycles, which make asphalt less elastic and therefore more prone to internal voids. Such voids allow water to penetrate into underlying layers, gradually eroding the structure.
In addition, heavy traffic loads, especially heavy vehicles, cause deformation of the surface layers: this results in water penetration, which “softens” the structure and makes it less resistant.
Anti-capillary drainage
The water capillarity, i.e. the ability of liquids to move in micro-spaces even against the force of gravity, is a rather complex concept closely monitored in the construction industry. With the help of pressures exerted on lower layers, water rises upwards, dragging the finer components of materials with it and causing deformation.
It is therefore necessary to provide a drainage geocomposite, a three-dimensional membrane obtained by bonding two or more synthetic components in order to convey fluids to the exterior and prevent them from rising.
You can discover all our solutions here.
Reinforcement
It may sometimes be necessary to install reinforcement grids, especially if there is a more or less pronounced slope that would cause a road shoulder to slide downwards.
The choice of the most suitable type of reinforcement, and therefore also of the position of the geogrid in the layering, clearly depends on the problems to be faced i.e. reinforcing the surface area to limit the spread of cracks to underlying layers, improving the load-bearing capacity and reducing the stresses transmitted to lower layers, or providing a separation (and anti-contamination) function.
Discover all our solutions here.
Stabilisation
During intervention works, softer soils may be encountered, which may be subject to instability or even collapse in the early stages of intervention works. Even if this should not jeopardise the feasibility of the works, there is still the risk that the minimum legal safety requirements will be compromised.
Also in this case, geosynthetic products are the solution to the problem, as they absorb tensions at least until the intervention work achieves structural stability.
Discover the solutions in the X-Grid line here.
- Published in Drainage geocomposites and membranes, Erosion mats, GEO, Geogrids, Roads
Why don’t puddles form on soccer fields?
Let’s take a step back: nowadays, synthetic turf fields are the most cost-effective solution for football clubs, for both the first team and the youth sector. So, the construction of a synthetic system is an opportunity not to be missed. It is therefore important to construct a synthetic field that is ideal for the type of use and level of play.
TeMa staff can assist in the construction – especially in the design phase – to define the characteristics of the synthetic turf field. We are very familiar with the different layers it is made of (sub-base, turf and sand, rubber or natural infill) and its various features recommended by experience depending on different climatic conditions. The initial step is also important for determining the procedure that any club – in almost all cases through the municipality, the owner – needs to follow in order to construct the most suitable synthetic field in terms of type and frequency of use.
The secret is…
…drainage. Having a quality sub-base is even more important than the surface turf. This is where the experience of TeMa steps in with the company’s drainage solutions, developed on 4 continents. They guarantee the timely disposal of water in the quickest possible time and the use of the field even in severe weather conditions.
Drainage of a synthetic turf field
On synthetic turf fields water drainage is horizontal: after stabilising and levelling the surface, an impermeable membrane is applied that prevents liquids from penetrating into the ground below, conveying them to the channels on the long sides of the field.
This prevents water from stagnating on the surface of the field, avoiding puddles and the removal of surface material.
Natural or synthetic turf for the field?
A natural grass surface requires more maintenance and higher costs: it needs to be cut at regular intervals, treated, fertilised and watered. Moreover, weather conditions may affect the use of the field.
By contrast, synthetic turf is more resistant to weather conditions. It can also be used intensively all the time, regardless of the season and requires much less maintenance: it only needs to be “combed” regularly to revitalise the turf.
In addition to the (much) shorter construction time, a factor that tends to make synthetic turf preferable to natural turf is its permeable capacity: the control over water filtration is clearly superior and the sub-base is designed to drain excess water during heavy rainfall and/or store it. This makes it easier to maintain favourable conditions for both the game and the durability of the field, while also protecting the health of the players.
What makes the field so even and linear?
Drainage geocomposites provide maximum performance.
Q-Drain ZW8 Football consists of a monofilament core bonded with two non-woven fabrics, to which a PE membrane can be added if required.
Q-Drain ZW8 WP Football, ideal for horizontal drainage applications, consists of a monofilament core bonded with a non-woven fabric and a waterproofing film.
To support these products, we recommend T-Kanal Football, a cement channel for perimeter drainage that contains a special drainage membrane. The system is made complete with a grid, fixings and T-Tape, for joining the rolls during installation.
- Published in GEO, Synthetic turf soccer fields - Accessories
The importance of geogrids in reinforced earth structures
In recent years, reinforced earth structures have been particularly popular in projects due to their excellent functional and aesthetic importance in the residential building and public building industries.
Such intervention works achieve the best results by allowing the soil and geosynthetics to “work in synergy”, each one with its own features of ensuring the stability of the work as a whole.
It’s easy to see the high environmental value of such solutions, but let’s take a closer look at the two major factors in reinforced soil works. In this way, we can understand how and why, working together, they lead to amazing results, also in aesthetic terms.
What are reinforced earth structures?
They are structural intervention works in various gradients and dimensions aimed at retention and/or stabilisation. We can identify a few main areas of application:
- Road and railway embankments.
- Restoration and consolidation of collapsed soil on a road.
- Construction of ramps for ascending and descending flyovers.
- Canal or river bank elevations.
- Rockfall barriers.
- Noise barriers along roads or railways.
- Widening of elevated car parks.
- Construction of terracing systems in vineyards.
- Soil consolidation at tunnel entrances.
What are geogrids and why are they often the best solution?
Soil has the intrinsic features of friction and compressive strength, but practically no tensile strength. This is not enough to ensure the stability of a structure.
Major slopes, weather conditions, proximity to embankments, etc. can erode soil, causing landslides and subsidence. For reinforced earth structures, it’s therefore necessary to use geogrids, two-dimensional structures horizontally inserted into soil, which integrate with it without deforming. Their open-mesh structure develops “passive” resistance, thereby increasing the stabilising effect.
This bonding exploits the abilities of the two construction elements, making the entire structure more efficient.
Naturally, the feasibility of retaining works needs to consider:
- the intrinsic characteristics of the soil, such as grain size, the degree of thickening and shear strength, as well as the dilatancy phenomenon;
- the characteristics of the geogrids, such as tensile strength and stiffness, the use of raw materials (polymers) that can also withstand harsh chemical and physical conditions (attacks by chemical agents, soil pH, etc.), and the appropriate geometric structure.
Greening
Eventually, grass will grow and none of the intervention work will be visible: a really attractive and natural reinforced structure. In addition to its aesthetic function, greening also plays an important role in helping the natural friction of soil.
Find out more about our products here.
Embankments in home gardens: small colourful islands
Made of masonry alone, embellished with different types and colours of plants and flowers, and of varying heights, embankments are often part of public buildings in parks and squares, but also a distinctive feature of private gardens. In the urban construction context, embankments can be borders for roadside verges, steps and flowerbeds, reaching a relatively low height, almost always less than 1 metre.
The provide a very attractive and organised visual effect and can be customised with the colours and types of plants you prefer. However, in order to achieve adequate stability for such intervention work, regulations require certain specifications to bear in mind for their construction.
A short and simple recap: let’s start by understanding what they are and how they are built.
What are embankments?
Embankments are accumulations of earth that form more or less evident differences in the level of the ground and can be natural or artificial. Natural embankments are caused and possibly accentuated by landslides, whereas artificial ones are man-made and consist of an earth fill supported by a wall, often in order to highlight the difference in level.
The risk of landslides
As mounds of earth, especially if they are of a certain height, embankments can be severely tested by atmospheric events, resulting in erosion and runoff due to rainwater.
Various characteristic elements can therefore be recognised:
- drainage and runoff systems in the underlying area where all rainwater accumulates;
- support and reinforcement of slopes, the part most susceptible to erosion;
- substrates and erosion control systems to allow plants to grow in the best conditions by sheltering the topsoil from the effects of the wind, sun and rain until the plants have become strong and well-rooted.
Block retaining walls and reinforcement grids
In order to prevent soil erosion or irrigation, embankments are reinforced with retaining walls in a combination of concrete blocks and geogrids, which meet geotechnical, building and architectural requirements.
TeMa Geo Solutions has the right products to create this type of construction.
For soil reinforcement we suggest X-Grid, reinforcement geogrids, which are knitted uniaxial geogrids made of high tenacity polyester yarns covered with a protective PVC layer.
For retaining walls, the range includes T-Block, a single concrete block for building reinforced walls.
The special feature of this product is the male/female joint, shaped directly on the block. This ensures maximum connection between the blocks, thus avoiding the use of mechanical fasteners, glue or mortar and making the wall stronger and more resistant to damage.
Find here all the specifications of the products mentioned.
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