Stabilised Soils on Construction Sites

Stabilising land with the using the propriety stabilisation binder SMR as recovery agent and binder is an extremely cost effective method of converting difficult or contaminated soils into purpose engineered construction materials.

Virtually any soils including most contaminated soils found on site can be recovered and improved using SMR.

By using the existing on site won soils or materials, construction can in most cases be commenced far quicker and with reduced planning and environmental constraint and delays.

Inaddition, the use of site won materials will lead to significant savings in lorry movements and big reductions in the environmental damage and overall carbon footprint of the project.

Recycling in-situ further reduces environmental impacts otherwise associated with the extraction of primary aggregates, the transportation of these materials to site and the transportation and land filling of excavated site waste.

The early establishment of a SMR stabilised working platform will provide a safe and sufficiently durable working surface on which trucks and construction plant, such as piling rigs and cranes can operate.

Platforms are essential when the onsite soils are weak giving insufficient support or if the existing ground conditions are wet or contaminated, and good design plan for the platform can ensure maximum efficiency of all future construction processes.

Clear economic and environmental benefits can be derived from the use of platforms, particularly:

路 Where increased use can be made of either site-won or recycled materials

路 When platforms can be used and re-used and/or reengineered for a variety of purposes throughout the construction process

路 When platforms can become future permanent works.

Stabilised working platforms formed by effectively engineering the existing site soils can be utilised many times through a construction site life-cycle; they may provide support for the ground works plant, early temporary access roads, avoiding degradation or improving the existing sub soils to enable them to be used for purpose engineered sub base, act as form work for casting pad foundations, provide a surface for steelwork erection and act as a structural element within a floor slab or pavement. In some circumstances recycled stabilised site aggregates can even be used as the piling columns themselves.

The stabilised bound product can be produced by either ex-situ or in-situ production methods.

Soils or granular materials can be blended with our binder in a stationary mixing plant and the resulting product placed and compacted by non-specialist plant.

The blending process for our recycled product can be carried out using a nearby “fixed plant” off site or “mobile plant” working within the project area, when space and through put volume allow.

The plant for laying and compaction of our product is similar to that required for the laying and compacting of other paving materials such as unbound layers or bituminous bound products.

Alternatively, the surface soils on site can be mixed in-place with our binder using specialist plant such as binder spreaders and rotavators.

As compaction can take place at any time within seven days of placement. This offers significant advantages to the contractor in both timing and use of equipment and labour.

A competent person from Soil Stabilisation Solutions Ltd will be able to estimate the likely volume/percentage of binder required from a visual examination of the site materials; this can be carried out initially so that a decision can be made, on economic grounds, on whether to proceed with the expense of laboratory testing of the site soils.

Some materials are difficult to stabilise because they are unsuitable chemically or may require excessive mechanical modification. Peat and other organic soils can delay the curing of the product and unless mixed with plenty of granular material will not compact well.

The binder can cope however with other difficult materials such as Sulphate rich soils which can cause swelling and disintegration of cement-bound layers and clays which other binders have difficulty drying.

When ex-situ mixing is the chosen method, the preparation, storage and laying of the bound product is really no different from that required for any imported material, and the usual care and consideration must be paid to its compaction, surface levels and profile.

In all cases Soil Stabilisation Solutions will be on hand in the initial stages to ensure methods are understood and the required specification is being met or bettered.

As with these alternative materials our recycled product should never be laid on frozen ground or on standing water. Otherwise seasonal working is no problem at all and normal summer and winter weather is not going to hold up work as the curing of the product is not temperature critical.

The approach to platform design should be related to the risks which have been identified in connection with the plant for which a platform is required and with theoperations to be carried out, as well as the pre-existing soil conditions.

A simple design approach for working platforms may be appropriate for many routine temporary platforms

Where the stabilised layer also forms part of future permanent works, a design method appropriate to that end use should always be carried out.

The design of a working platform is a geotechnical design process and should be carried out by a competent person.

The designer should have full access to the health and safety plan, including the desk study and all other site investigation information. This information we provide is not intended to replace or reduce the designer’s input, but rather to inform and educate the designer and his team of alternative and new construction developments.

The platform level may be dictated by construction requirements rather than by the final design of the permanent structure.

This should be considered early in the design and construction process to ensure that where possible working platforms can be re-used for other purposes.

Attention needs to be given to the edges of working platforms. It should be determined how near the edge of the platform plant and vehicles can be permitted while avoiding instability or break off.

With other stabilisation system platforms a minimum distance of half a machine width is usually required for tracked plant to avoid degradation and break off, with our SMR binder this is not such a critical factor as the bound material will very quickly attach itself to the base on which it is laid and geotechnical engineer also to the surrounding ground, as the copolymer molecules (seeking out any moisture) form bonds between the platform and surrounding soils.

Sloping sites do present particular problems for stability, and these inherent problems should always be addressed in the platform design.

As a general rule for site platforms our binder will be added to achieve strengths of around 2N/mm2 (strength class C1.5/2.0) which has been found reasonable for platforms for most construction activities.

Different construction processes carried out on or through the platform may impose greater strength requirements that need to be taken into account in the design of different areas of the platform using batch controls this strength variation can easily be engineered in to the product with SMR.

A platform that is very strong though it may form an ideal running surface for plant could cause problems in the construction process if drainage runs need to be dug. We feel our product is unique in this aspect as the bound strength increases without ever becoming rigid and can still be worked up to high strength levels.

The bound product does have very low permeability, which is beneficial from a construction point of view, but means that drainage design will be critical, to ensure that the platform remains suitable for use and will not carry standing water.

In general this can be carried out by careful construction of the platform layer. Falls can be constructed into the platform by means of grading during final compaction.

In all cases the requirements of the construction timescale should be taken into account – winter working may require drainage design for heavier rainfalls and account to be taken of the raising of the water table beneath the platform.

Similarly ice forming on the platform due to the presence of standing water can render construction activities dangerous.

In the worst cases it may be necessary to put in place a granular topping layer or wearing course.

The incorporation of the initial platform into the permanent works can save significantly on cos

Where this is pre-planned there is a tendency on site to take greater care of the platform when it is seen as part of the permanent structure.

Examples of subsequent uses of the platform may be:

路 Re-use as temporary works for later construction activities, such as use of the platform for form work

路 Re-use as pavement layer, for car parking and access road

Reuse may, require reworking of say the top 30mm of material and/or even re-grading.

With an SMR bound platform, these supplementary works can be carried out easily and quickly on site.

 

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