PVD Vertical Drains

GEOTEXTILE / PREFABRICATED VERTICAL DRAINS (PVD) TESTING

Ensure unstable soil conditions in embankment construction meet requirements

Ensure unstable soil conditions in embankment construction meet requirements

WHAT IS GEOTEXTILE / PREFABRICATED VERTICAL DRAINS (PVD)?

Many times, the soil integrity for construction sites required for residential, commercial and industrial properties, infrastructure like roads, highways, bridges, railways, airport runways, ports, dock yards, and others is not conducive for building structures. Excessive settlement can take time for soft compressible soils like clay or silt clay with low permeability as they have a lower load bearing capacity. 

To strengthen the weak saturated soil and to expedite preconstruction slow draining soil consolidation, a network of prefabricated vertical drains (PVD) also called as ‘wick drains’ are used for creating drainage pathways into the pore soil. These wick drains are then laid vertically in soft soil with the help of a mandrel/ vibratory hammer /static method that are mounted on a crane or excavator. A surcharge or preloading program is then applied to accelerate the process of soil consolidation and settlement. 

The prefabricated vertical drains (PVD) are made up of a core material, usually of plastic that is wrapped with the spun-bond non-woven geotextiles as an outer layer and acts as a filter fabric. The geotextile filters the soil from entering the water channels and flooding the drain. Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain. They have moulded channels that accelerate the soil consolidation process and help to siphon the trapped water in the soft soil strata and bring it to the surface. The duration taken for consolidation of the cohesive soil (sticky soil) depends on the quality of the geotextile, surcharge weight, soft or sand layer of soil and the design and strategic placement (gap between the drains) of the wicks.

In order to determine if a geotextile material is suitable for a particular application it must undergo appropriate mechanical testing procedures. The most common forces a geotextile experiences during its application are tensile and puncture. Each of these forces can cause the premature failure of a geotextile and lead to catastrophic events. 

IMPORTANCE OF PVDS IN SOIL CONSOLIDATION

Prefabricated vertical drains (PVDs) are a key component in soil consolidation projects, where they are used to accelerate the process of soil settlement and enhance the strength of the soil. PVDs are usually installed vertically into the soil to help with water drainage, which allows the soil to consolidate faster.

PVDs are often used with other techniques like surcharge loading to accelerate the consolidation process and attain the desired soil density and strength, which involves adding weight to the soil's surface to compress it further. PVDs are an effective and cost-efficient solution for many construction and infrastructure projects, as they reduce the time required for soil consolidation and improve soil strength. Prefabricated vertical drains testing is also important in soil consolidation projects to ensure that the drains are properly installed and working as intended.

ADVANTAGES OF PREFABRICATED VERTICAL DRAINS

Many construction and infrastructure projects widely use Prefabricated Vertical Drains (PVDs) because of their numerous advantages over traditional soil consolidation methods.

  • One of the main advantages of PVDs is accelerated consolidation, achieved by the rapid dissipation of excess pore water pressure through the vertical drainage path created by the PVDs. It helps to significantly shorten the time required for the soil to settle and become stable enough to support structures or heavy loads.
  • PVDs also increase the shear strength of the soil, which is essential for building foundations and other load-bearing structures. PVDs can prevent soil liquefaction during earthquakes and other natural disasters by providing a firm and stable base.
  • Furthermore, creating a more uniform and consistent soil density using PVDs helps to reduce residual settlement, which occurs when the soil gradually sinks after consolidation. It allows the even distribution of load across the soil, improving stability.
  • Finally, PVDs also improve drainage paths, preventing soil erosion and other problems caused by excess moisture. It helps maintain the stability and integrity of the soil over time.
  • To ensure the effectiveness of PVDs, regular prefabricated vertical drain testing is essential. It helps monitor the consolidation process and make any necessary adjustments. With proper testing and maintenance, PVDs can provide a cost-effective and practical solution for many construction and infrastructure projects.

A well tested good quality Geotextile/Prefabricated Vertical Drains (PVD) installation can have several benefits:

  • It improves the permeability of the soil and brings upon faster settlement.
  • As the pore water drainage path is shortened, the soil consolidation takes place in weeks instead of years, thus, enabling you to expedite construction and save cost.
  • Wicker drains are more economical and cost-efficient than prefabricated drains
  • Together with surcharge, Geotextile/Prefabricated Vertical Drains (PVD) can considerably reduce the time of soil settlement.
  • The installation of Geotextile/Prefabricated Vertical Drains (PVD) is hassle-free and does not take a long time to implement.
  • Dewatering of pore water leads to soil improvement in a short period of time.
  • Most of the Geotextile/Prefabricated Vertical Drains (PVD) are naturally biodegradable and will not leave any residual plastic.
  • Geotextile materials prevent the erosion of earth and similar substances after the area has been altered due to construction usually due to civil engineering applications such as roads, pavement, bridges, embankments and retaining walls.

The residual settlements are also controlled to a certain extent through Geotextile/Prefabricated Vertical Drains (PVD).

WHEN TO USE PREFABRICATED VERTICAL DRAINS

Prefabricated vertical drains (PVDs) are a cost-effective and practical solution for many soil consolidation projects. However, they are only sometimes necessary or suitable for all soil types and projects. Here are some factors to consider when deciding when to use PVDs:

A. Soil types suitable for PVDs: PVDs are best suited for cohesive soils, such as clay and silt, which are prone to high levels of settlement. In addition, PVDs find application in other soil types with poor drainages, such as sand and gravel.

B. Soil properties that require PVDs: PVDs are particularly useful in soils with low permeability, high water content, and high compressibility. These soil properties can make traditional consolidation methods, such as surcharge loading, ineffective or impractical.

C. Types of projects that require PVDs: Engineers and contractors commonly use PVDs in a wide range of construction and infrastructure projects, including highways, railways, airports, and ports. They are also useful in building projects where settlement and stability are critical, such as high-rise buildings and hospitals.

Before deciding to use PVDs in soil consolidation projects, conducting proper PVD testing and analysis of the soil conditions is important. Determining the use of PVDs should be based on soil properties and project requirements.

APPLICABLE AREAS FOR PREFABRICATED VERTICAL DRAINS (PVD) INSTALLATION

Various construction and infrastructure projects use prefabricated vertical drains (PVDs) for soil consolidation. These drains are particularly useful in areas where the soil is soft or compressible and where poor drainage is a concern. PVD installation is suitable for the following areas:

  1. Land reclamation projects: PVDs can improve soil stability and support heavy structures on reclaimed land.
  2. Road and highway construction: PVDs can help stabilise soft soil and prevent damage to roads and highways.
  3. Airport and port construction: PVDs can provide stable and reliable soil conditions for runways, taxiways, and other airport infrastructure.
  4. Industrial and manufacturing facilities: PVDs can help stabilise soil in industrial and manufacturing facilities, preventing damage to equipment and structures.

It is important to conduct proper PVD testing and soil condition analysis to ensure the effectiveness of PVDs in improving soil consolidation. The installation of PVDs can significantly reduce the time required for soil consolidation, making them a cost-effective solution for many construction projects.

LIST OF OUR ACCREDITED PRECONSTRUCTION SOIL CONSOLIDATION TEST METHODS

  • ASTM D4491 – Permittivity  
  • ASTM D4533 – Trapezoid tearing strength
  • ASTM D4595 – Wide-width tensile strength
  • ASTM D4632 – Grab strength
  • ASTM D4716 – Discharge flow rate  
  • ASTM D4751 – Apparent opening size
  • ASTM D4833 – Puncture resistance
  • ASTM D5199 – Thickness 
  • ASTM D5261 – Mass per unit  
  • ISO 9863-1    – Thickness
  • ISO 9864       – Mass per unit  
  • ISO 10319     – Wide-width tensile strength
  • ISO 11058     – Permeability 
  • ISO 11236     – Static puncture test (CBR test)
  • ISO 12958     – Water flow capacity
  • ISO 13433     – Dynamic perforation test (cone drop test)

ACCREDITATION AND RECOGNITION

TÜV SÜD laboratories are accredited to the designated geosynthetic test methods in accordance with the Geosynthetic Accreditation Institute – Laboratory Accreditation (GAI-LAP).

WHY CHOOSE TÜV SÜD’S GEOTEXTILE / PREFABRICATED VERTICAL DRAINS (PVD) TESTING SERVICES?

TÜV SÜD is a trusted, independent third-party solutions provider that carries out impartial analyses and tests of your structures. We carry a variety of tests on Geotextile/Prefabricated Vertical Drains (PVD) to ensure that your preconstruction soil consolidation through wicker drain installation will be conducted in a structured and seamless manner. This will help you mitigate the risk of delay in the project completion and accidents.

Our experts actively participate in the preparation of directives and standards governing safety of engineering structures. This ensures they are familiar with all relevant requirements and regulations. We have decades of international experience in the real estate and infrastructure sector. In addition, we are accredited according to ISO 17020 to conduct independent inspections for quality assurance.

 

For more details, contact us today.

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