Fill Drying
Hiway Stabilizers' specialist Fill Drying fleet is equipped to handle the most demanding of sites. Fill Drying can incorporate a variety of specialist binders to achieve instant drying and soil conditioning, allowing earthwork projects to continue without weather delay and without the threat of post construction failure.
Hiway Stabilizers pioneered the development of the Fill Drying process in New Zealand.
The process enables fill materials (soils) which are often significantly wet of optimum moisture content to be used instantly, thereby enabling earthworks operations to continue when climatic conditions are unfavourable.
The Fill Drying is generally carried out in conjunction with earthworks operations where insitu materials have very low strength due to high moisture content and is unable to be handled or achieve structural requirements. It is particularly well suited to sites with tight construction programmes, winter earthworks programmes or sites with limited drying areas.
Conditioning Of Wet material The Easy Way
Fill Conditioning of wet material using lime is generally always more cost effective than cut to waste and importation of good quality fill material. It is also often cheaper than conventional earthworks drying techniques which are time consuming and rely on good weather conditions.
Fill Conditioning using lime oxide or lime oxide blends provides immense benefits to the earthmoving contractor. By fill conditioning a wet ground after a wet weather episode, earthworks operations can continue immediately thereby limiting unproductive down time. The operation is fast and effective, enabling large volumes of material to be dried instantly. Hiway Stabilizers plant is purpose built to handle almost any ground condition. We have achieved up to 3,000m³ (solid) per day with one fill conditioning crew on past projects which means that the earthworks contractor is able to move this quantity with the confidence of achieving specified earthworks testing criteria.
The Process
The process uses calcium oxide or calcium oxide blends as the conditioning agent. The grade of calcium oxide used is of very fine particle size to enable maximum coverage of the soil particles when mixed.
The operation is carried out using specialised purpose built machinery. This is usually of tracked configuration which offers very low ground pressure. This plant is able to work on very soft and wet material and is designed to ensure controlled, accurate and consistent spread of additive and depth of mixing. Non specialist rubber tyred plant cannot deliver the same degree of precision as the tracked equipment as it has higher ground pressure and inevitably loses traction, slides or cannot maintain a consistent ground speed. Hiway Stabilizers plant is capable of conditioning cut/fill layers of up to 500mm in depth.
The conditioning agent is delivered in pressurised tankers to site and pneumatically transferred from the tanker to the tracked spreader truck. For sizeable contracts Hiway Stabilizers has a tanker and compressor stations on site to store agents to further improve on site efficiency.
Once the agent is received the material is applied at the prescribed rate. This can be spread over almost any material or condition including puddles or silt traps. The design application rate can be varied over a site depending on the variation in insitu and optimum moisture contents and the types of soils encountered. Once spread the conditioning agent is then mixed into the wet material, using a tracked stabilising machine. The agent is mixed into the soil material unslaked, so that the excess water within the soil is used to hydrate the agent. This hydration process effectively dries back the wet material, producing a "mechanical" strength gain and is the key to the success of the operation.
As well as this "mechanical" strength gain there are also chemical strength gains as per the normal lime stabilisation process. This chemical strength continues with time and can be particularly beneficial if the site requires haul roads or trenching work to be carried out at a later date and the material then encountered is fully stabilised.
Design / Testing
The design process for this operation should be approached pragmatically and does not usually require the same level of technical input as normal stabilisation. Laboratory testing can be undertaken to confirm the natural strength of the material to be treated at its natural (often saturated) water content versus the strength achievable once dried back with the use of the chosen conditioning agent.
However, due to at times, the significant variation in on-site soil types and moisture contents, the reliance strictly on laboratory test results is often not a practical procedure. It should however, not be discounted as it provides a good guide when setting (and adjusting) application rates.
Designs usually allow for anywhere between 1% and 3% of conditioning agents to be used, however, on rare occassions up to 5% maybe necessary.
The operation requires careful control throughout its implementation. All spread rates are checked and recorded for each area of stabilisation completed. The depth of conditioning is also checked and recorded.
The performance of the treated material is of paramount importance and is usually controlled using traditional earthworks testing equipment which may consist of Pilcon Shear Vane or Scala Penetrometer to test strength and Nuclear Densometer or Core Cutter to test compaction.
Summary
The fill conditioning process developed by Hiway Stabilizers has resulted in significant benefits to subdivision land developers where the completion of earthworks is critical to section sales and also to infrastructure projects where earthworks completion is critical to the civil works construction program.
Hiway Stabilizers are equipped to tackle the most demanding of sites, achieving almost instantaneous results and high productions. Our specialist fill drying plant includes Komatsu CS360 tracked stabilising machines, Mitsubishi LD1000 tracked spreader trucks, six wheel drive spreader trucks and Komatsu BZ200 soil recyclers as well as our conventional stabilising hoes and spreaders which can be used where conditions allow.
The Fill Drying process provides a real and economic solution to an age old earthworks dilemma enabling projects to be completed on time when climatic conditions would dictate otherwise.
