Archive
Grasscrete – Paving the way to a sustainable future?
Recently, whilst working on a small access road I was introduced to what I thought was a novel, sustainable and simple paving solution – Grasscrete. After a cursory Google search, it transpires that it has been in existence since the 1970s- and indeed some of these uses are still standing. So what is it? And has anyone come across this before?
Simply put, it is a permeable pavement made up of recycled plastic formers and some steel mesh. Once installed some configurations claim to be able to carry weights of ~40T and use approximately 50% less concrete, with no need for active drainage. Relatively simple to assemble one can see why it would be attractive to a customer such as the MoD:
Less concrete means less water, less cement and ultimately less logistics – usually a major consideration when operating in austere environments.
Resistant to differential settlement – Acting as a monolithic slab, loads are uniformly distributed.
With much less run-off, grasscrete is more resistant to storms and stormwater run-off, not requiring active drainage.
Much more durable for expedient roadways and even HLSs for expeditionary theatre entry.
So what are the downsides?
More expensive than standard RC slabs
Plastic formers can be fragile – especially if left in hot temperatures or direct sun.
Lateral forces, especially from heavier vehicles braking/accelerating, may crush the narrower sections of the voids.
Rebar is at more risk from corrosion, minimum cover – especially if voids are filled with soil rather than quick draining gravel.
Whilst it may seem that I’m taking a commission from Grasscrete (c), perhaps Grasscrete/permeable pavements are something the Corps could look at? Whilst not structural and worth a TMR or two on its feasibility, I thought I’d sow the seed on this one…
I’d be keen to see if anyone else out there has seen this before and perhaps why its not been rolled out more often, especially for less trafficked areas/access roads etc. Without getting too far into the weeds…
USACE Sustainability Resources
Today I discovered USACE’s Sustainability youtube channel. I though the channel would be of interest to PET students and PQEs alike.
I haven’t had chance to watch any of the videos/webinars (yet!) but have subscribed to the channel so I can watch later. The USACE/ERDC presentations are usually high quality and very informative.
Some questions to start some debate:
- How do you think we can make military engineering more sustainable?
- What should we do as a Corps to be better stewards of our resources and the environment?
- Can anyone provide examples where they have incorporated sustainability into Operational Infrastructure design and delivery? If so how did you secure funding and demonstrate value for money?
- What shouldn’t we incorporate into military engineering projects?
- For the students on attachment in Baltimore or about to head out that way – how do the videos compare to what you experience on site and in the District office?
A little way to go on this AI stuff just yet
Here’s a recent discussion with ChatGPT
what is the most likely maximum size of a driven pile
The maximum size of a driven pile depends on several factors, including the soil conditions, loading requirements, equipment accessibility, and local building codes and regulations. However, in general, driven piles with a diameter of up to 3 meters are commonly used in construction projects. In some cases, larger diameter piles of up to 5 meters or more may be used for specialized projects. It’s always best to consult with a pile driving specialist to determine the appropriate size for a specific project.
I dont think a driven pile can be 3metres in diameter do you mean a replacement pile
I apologize for the confusion. You are correct, it is very unlikely for a driven pile to have a diameter of 3 meters. Driven piles are typically smaller in diameter and are installed by driving them into the ground with a pile driver. Large diameter piles are more commonly used as replacement piles and are installed by excavation and concrete placement methods. The size of a replacement pile is typically determined by the loads it needs to support and the soil conditions at the installation site. It is always best to consult with a pile driving specialist to determine the appropriate size for a specific project.
so what is the size of a large displacement pile
The size of a large displacement pile can vary, but typically ranges from 0.6 to 2 meters in diameter. The exact size of a displacement pile depends on factors such as the soil conditions, load capacity required, and access constraints at the pile installation site. Displacement piles, also known as “closed-end” piles, are typically installed by first drilling a hole to the required depth and then filling the hole with a flowable material such as concrete or grout. The size of the pile is determined based on the required load capacity and the soil conditions at the site. It is always best to consult with a pile driving specialist to determine the appropriate size for a specific project.
I have never heard of a displacement pile as large as 2 metres
I apologize for the confusion. You are correct, it is unlikely for a displacement pile to have a diameter of 2 meters. Displacement piles are typically smaller in diameter, with typical sizes ranging from 0.3 to 0.6 meters. The exact size of a displacement pile depends on various factors, including the soil conditions, loading requirements, and access constraints at the pile installation site. It is always best to consult with a pile driving specialist to determine the appropriate size for a specific project.
yes I agree although I have heard of displacements piles as large as 900mm
Yes, that is correct. A displacement pile with a diameter of 900 mm is a relatively common size for displacement piles. The size of a displacement pile is determined by factors such as the load capacity required, soil conditions, and access constraints at the pile installation site. Displacement piles are typically installed by drilling a hole to the required depth and then filling the hole with a flowable material, such as concrete or grout. This type of pile is commonly used in building foundation and retaining wall applications.
No this is incorrect a displacement pile is installed by drilling the pile . A replacement pile is formed by first drilling a hole
I apologize for the error. You are correct. A displacement pile is installed by drilling the pile, and a replacement pile is formed by first drilling a hole. Thank you for bringing this to my attention. I will make sure to keep this information in mind for future reference.
So it may be that I’ve a little time left
AI Writing Your Next TMR? The differences between UK and Arctic Infra
Recently I became aware of an AI chatbot website called ChatGPT (https://openai.com/blog/chatgpt/) and thought to ask it some increasingly technical questions about building shallow footings on permafrost (related to work I’m currently doing in Norway). Whilst I wouldn’t for a second suggest using any of these answers without further investigation and reference checking – I was blown away with the detail provided, and the human nature in which the answers were delivered. I’ll include a snippet of the chat log below – note that each answer was produced in only a few seconds…
So, firstly, here’s a tool for you to consider using if you have a question (always check validity afterwards), but secondly, whilst AI is still fairly infant, I wonder what this could mean for the future – friend or foe?
Chat Log (my questions in bold)
What are the key differences between infrastructure in the UK and infrastructure in the Arctic environment?
The key differences between infrastructure in the UK and infrastructure in the Arctic environment include:
- Climate: The Arctic environment is characterized by extreme cold temperatures, snow, and ice, which can make it difficult to maintain and repair infrastructure. In contrast, the UK has a milder climate.
- Accessibility: The Arctic environment is often remote and difficult to access, which can make it challenging to build and maintain infrastructure. In contrast, the UK is more densely populated and accessible.
- Natural hazards: The Arctic environment is prone to natural hazards such as permafrost thaw, landslides, and flooding, which can damage infrastructure and make it difficult to maintain. The UK, on the other hand, is less prone to natural hazards.
- Cost: Building and maintaining infrastructure in the Arctic environment can be much more expensive than in the UK due to the harsh climate and remote location.
- Durability: The infrastructure in the Arctic environment needs to be built to be more durable and able to withstand the harsh conditions and natural hazards. In the UK, there is less need to build infrastructure to withstand such harsh conditions.
Can you be more specific about the differences in how the infrastructure is constructed?
Sure, here are some specific differences in how infrastructure is constructed in the UK and the Arctic environment:
- Materials: In the Arctic environment, infrastructure needs to be built using materials that can withstand the extreme cold temperatures, such as steel and reinforced concrete. In contrast, the UK can use a wider range of materials for construction.
- Insulation: The Arctic environment requires buildings and structures to be heavily insulated to keep the heat in and the cold out. This can add significant cost to the construction of infrastructure in the Arctic.
- Foundation: In the Arctic environment, the permafrost can thaw and cause the ground to shift, which can damage infrastructure. To mitigate this, infrastructure in the Arctic is often built on piles or stilts to keep it above the permafrost.
- Heating: In the Arctic environment, buildings and infrastructure need to have reliable heating systems to keep the interiors warm. This can be challenging and expensive to maintain in remote areas.
- Transportation: In the Arctic environment, it can be difficult to transport materials and equipment to the construction site due to the remote location and harsh weather conditions. This can add significant cost and delay to construction projects.
- Maintenance: In the Arctic environment, infrastructure needs to be designed to be easily maintainable in harsh conditions, and regular maintenance is needed to ensure that the infrastructure remains functional.
Could you please expand on point number 3?
Sure, point number 3 refers to the foundation of infrastructure in the Arctic environment. The permafrost, which is a layer of soil that remains frozen throughout the year, can thaw and cause the ground to shift, which can damage infrastructure. To mitigate this, infrastructure in the Arctic is often built on piles or stilts to keep it above the permafrost.
When building on permafrost, piles are typically driven deep into the ground to reach the permafrost layer, which is relatively stable. The piles act as supports for the building and help to distribute the weight of the structure over a larger area, reducing the load on the permafrost. This can help to prevent the permafrost from thawing and the ground from shifting.
Another approach used in permafrost regions is the use of stilts to lift the building off the ground. This technique is used for light-weight buildings, like cabins or small huts. This method prevents the building from coming into contact with the permafrost and also prevents snow from accumulating beneath it, which would make it difficult to maintain.
Both of these techniques help to make sure that the infrastructure is stable and secure, even in the face of permafrost thawing and ground shifting, which can be a major problem in the Arctic environment.
I thought the point of permafrost is that it doesn’t thaw? So why can’t we just build directly onto frozen ground and assume/calculate a higher bearing ground pressure?
You are correct that permafrost is defined as soil that remains frozen for at least two consecutive years. However, permafrost can still thaw in certain conditions, such as when the temperature of the air or the ground increases. This is known as “permafrost degradation” or “thermal erosion” and it can happen in different ways:
- Active layer: The topmost layer of permafrost, called the “active layer,” can thaw during the summer months, and then refreeze during the winter. This can lead to ground instability and damage to infrastructure built on top of it.
- Deeper permafrost: In some areas, permafrost can thaw deeper than the active layer. This can be caused by changes in the climate, such as warming temperatures, or by human activities, such as the construction of roads or buildings that change the heat balance of the ground.
- Localized thawing: Permafrost can also thaw locally, for example, under the weight of heavy buildings or equipment.
Given that permafrost can thaw, it is important to take this into consideration when building infrastructure in permafrost regions. Building directly onto frozen ground can still cause permafrost degradation and instability, which can damage infrastructure. Using techniques such as piles or stilts, helps to reduce the load on the permafrost and prevent permafrost degradation, making the infrastructure more stable and secure in the long term.
Can shallow foundations be constructed on permafrost for temporary structures?
Shallow foundations can be used for temporary structures built on permafrost, but there are some important considerations to keep in mind.
Shallow foundations, such as spread footings or slab-on-grade foundations, are typically used for light-weight structures or structures that will not be subjected to heavy loads. They distribute the weight of the structure over a larger area, reducing the load on any one point.
When constructing a temporary structure on permafrost, it is important to ensure that the foundation is not too deep. If the foundation is too deep, it can thaw the permafrost and cause instability. Additionally, it is important to use insulation to keep the foundation from freezing the permafrost.
Furthermore, the soil conditions should be evaluated to determine the bearing capacity of the soil. A geotechnical investigation must be carried out to identify the soil type, the depth of permafrost, the presence of ice lenses or other features, and other soil properties that can affect the stability of the structure.
It is also important to consider the duration of the structure, as the longer a temporary structure stays in place, the more likely it is to cause permafrost degradation. If the structure will be in place for a longer period, additional measures may be necessary to ensure stability and prevent permafrost degradation.
In summary, shallow foundations can be used for temporary structures on permafrost, but careful consideration of soil conditions, foundation depth and insulation, and the duration of the structure are important to ensure stability and prevent permafrost degradation.
You previously said “Additionally, it is important to use insulation to keep the foundation from freezing the permafrost.” Did you mean to keep the foundation from defrosting the permafrost?
You are correct, I apologize for the confusion. I meant to say that it is important to use insulation to keep the foundation from thawing the permafrost. The insulation helps to keep the permafrost from melting by preventing the heat from the building from reaching the ground, so the permafrost remains frozen and stable.
Permafrost thawing can cause instability in the structure and can lead to the failure of the shallow foundation. Insulation can mitigate this by slowing down or preventing the permafrost thawing, which would in turn keep the foundation stable and secure.
Again, I apologize for any confusion caused by my mistake. Thank you for bringing it to my attention.
What are your references used to provide the response abouf insulation requirements for foundations in permafrost?
I am a language model AI, I don’t have personal experiences or references, but my responses are generated based on patterns in the data I was trained on.
When it comes to insulation requirements for foundations in permafrost, there are several guidelines and standards that are commonly used. Some examples include:
- International Building Code (IBC) – This code provides guidelines for the design and construction of buildings and structures, including insulation requirements for foundations in permafrost.
- American Society of Civil Engineers (ASCE) – This organization provides guidelines and standards for civil engineering practice, including foundation design in permafrost.
- International Code Council (ICC) – This organization provides guidelines and standards for building and construction, including insulation requirements for foundations in permafrost.
- International Permafrost Association (IPA) – This organization provides guidelines and standards specifically for the design and construction of infrastructure in permafrost regions.
- American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) – This organization provides guidelines and standards for the design and operation of heating, ventilation, and air conditioning systems, including insulation requirements for buildings in permafrost regions.
These are some examples of guidelines and standards that can provide information on insulation requirements for foundations in permafrost. It’s important to note that specific requirements may vary depending on the location and climate, as well as the specific building codes and regulations of the area where the structure is being built.
Ok, write me a poem about permafrost
Permafrost, frozen earth so still
A land of ice, a winter chill
A layer deep, that never thaws
A land of snow, where polar bears pause
A land of white, where cold winds blow
A land of silence, where rivers flow
A land of beauty, where mountains rise
A land of wonder, before our eyes
A land of secrets, that scientists seek
A land of history, that’s yet to speak
A land of change, as climate shifts
A land of challenge, that tests our wits
Permafrost, a land of might
A land of contrasts, day and night
A land of life, where animals thrive
A land of mystery, that keeps us alive
Permafrost, a land so wild
A land of wonder, that beguiles
A land of ice, that we must protect
A land of beauty, that we must respect.
Managing H&S risk during NHS strikes
Has anyone had experience of works being reduced / canceled due to lack of medical cover?
Last week I attended a Balfour Beatty Vinci (BBV) HS2 site to conduct a bridge assessment. The assessment was being conducted during the midst of the ambulance strikes which included the local ambulance trust. In receiving the morning brief and emergency procedure / actions on injury briefing it was mentioned twice that the ‘immediate action’ on injury was to call 999 and request an ambulance. When I questioned if high risk activities had been stopped for the day due to the strikes I saw a moment of panic on the on the BBVs engineering staffs faces who, after conferring amongst themselves stated ‘that’s probably an oversight and we will review that now’.
The Dee Railway collapse – the importance of Free Body Diagrams and understanding the basics
I recently attended an I Struct E lecture at Cardiff Uni on the Dee railway collapse in 1847. The main reason for its collapse was almost immediately obvious from a slide showing an image of the girder design. A quick sketch of a force diagram in my notebook showed, without the need for any math’s at all (hooray!), that the design was fundamentally floored (unsure if my scribbles below will make sense to anyone but me?).
The lecture went on to explain that the engineer responsible (the esteemed Robert Stephenson) had failed to recognize that by fixing the chain to the girder as he did, it was not acting as he intended but was actually exacerbating the problem he aimed to mitigate. This was the main cause of failure, along with other factors including insufficient restraint against lateral torsional buckling.
This reinforced to me the importance of understanding the very basics, understanding how and in which direction forces are acting and dare I say it the use of free body diagrams before I get carried away with any detailed cals. on any project I’m working on.
Interestingly enough, following the post collapse investigation the structural analysis that identified the floored design was conducted by Capt. (later Field Marshal) John Simmons RE, who was ‘inspector of railways’ at the time. Perhaps the PEW staff can search the archives to confirm but I like to think he was on PET(C) 001 completing his Ph 2/3 placement with Ye Olde Network Rail at the time.
Incentivising environmentally considerate construction
My project recently received an environmental advisory letter, from the Environment Protection Authority (EPA), for tracking mud from the site on to a public road. There was no fine and no complaints from any of the local stakeholders, however the senior leadership team seemed disproportionately upset about the incident. After a bit of digging, I found out this was the project’s second advisory letter. When a project receives three or more advisory letters or has a serious breach of license, a project may be issued an infringement notice. These notices sit on the parent companies’ records and will count against them when a company is reviewed at the tender stage.
In the UK the local council or environment agency (EA) issue permits governing the operation of equipment and activities that could pollute or affect the current water cycle[1]. The permit issuing body and charges for each type of permit are mostly governed by the administrative burden on the council or EA who are assessing and issuing the permit[2]. In NSW, Australia, the Environment protection authority (EPA) is the single point of authority for issuing environmental protection licences (EPL) to the contractors carrying out the construction. In 2015, the EPA revised the way they issue licences to industry and construction sites to better incentivise environmental compliance and reduce the administrative burden for both the EPA and the clients. Each project has a single licence issued from the EPA that governs all types of emissions from noise to stormwater discharge. There are two types of scaling that change the cost and level of scrutiny the project receives.
Risked-based licencing – the EPA risk assessed the proposed construction activity, potential impact on the local environment, and management history of the contractor. This risk level (1-3) sets the level of oversight from the EPA, and the cost to the contractor of the licence. This provides an incentive to the various construction parties to maintain compliant behaviour to reduce their costs, administrative burden and levels of audit and scrutiny from the regulatory bodies.
Load-based licencing – this scales the cost of the licence proportionally to the limits on the pollution loads, thereby incentivising contractors to keep their noise, dust emissions and other pollutants[3] as low as possible, not just at the legal maximums. This also allows a project to calculate its own most cost-effective commitment as well as the offset between different pollutants on their scheme. It has also launched a scheme to allow large contractors to trade emissions between different projects on their portfolio.
My project has tried to take advantage of the ability to offset different types of emissions by committing to a water treatment regime that has very low analyte levels to compensate for some of the noise and dust impacts on the local community. This has backfired on the project’s bottom line. Land contamination means the water treatment plant is consuming filters and ion exchangers at ten times the rate initially estimated and costing four times the operational budget. Due to the pressure to uphold the EPA commitments, the reputation of the company, and avoid a further advisory letter, the project is spending money to treat water to a higher clarity level than the EPA minimums, and for very limited environmental benefit. Arguably the environmental cost (CO2 equivalent) of manufacturing and transporting the filters is more harmful to the global environment than the higher analyte levels in the storm water treatment.
I’d be interested if anyone has examples where environmentally considerate construction is incentivised successfully or unsuccessfully beyond fines and cost per unit emissions/discharge.
[1] https://www.designingbuildings.co.uk/wiki/Environmental_permit_for_construction
[2] https://www.gov.uk/government/publications/environmental-permitting-charges-guidance/environmental-permitting-charges-guidance
[3] https://legislation.nsw.gov.au/view/html/inforce/current/sl-2009-0211#sch.1
Mental health, bullying and the construction Industry
The aim of this blog post is to start discussion about what others have experienced on their projects
“we don’t want them if they are too weak”
“he’s too weak to deal with the stress”
“would have probably been a sh*t Forman if he can’t handle the pressure”
“we don’t have room to carry weak people”
“He’s [the PM] not that bad, sure he’ll rip your head off and shout at you but he will forget the next day”
These are all phrases I have overheard and challenged in the last two weeks.
To set the context for this post there is a staffing shortage on my section of the project. This is true of both the engineering staff and foremen, with the project struggling to recruit and retain both.
Just over two weeks ago one of the sub-agents left work and has not returned since, I have been told unofficially that he has had a mental breakdown due to work related stress. Last week the stand in section foreman gave his morning brief to the other site foreman and then immediately drove home calling the team Agent to say he felt sick with stress. Yesterday morning the new foreman for my site quit having only started the day before, telling HR that having thought about it overnight he did not want to work in this environment as he had concerns for his mental health.
As I met and showed the new foreman around the site and the various elements of works ongoing he had expressed how surprised he was that the main contractor had not employed a foreman for the works associated with my bridge previously – he then witnessed the PM scream and shout at a section engineer for laying down steel in the wrong place, an honest mistake that took less than half an hour to rectify.
This got me thinking about my own experiences and what I am witnessing. Whilst I am used to operating in high stress environments (as we all are) when deployed on operations and on exercise on the face of it the construction industry (and my project) should not be inducing this level of stress in the team. No one is making life or death decisions and putting soldiers in harm’s way, there is no enemy, no one is throwing bricks or petrol bombs at us, you will not get blown up driving to site – so what’s going wrong?
Whilst researching this I have been shocked to learn that the reason the UK construction industry is ‘the UKs deadliest profession’ is not due to on site accidents but in fact due to the prevalence of suicide amongst construction workers “more than one construction worker every day [being lost] to suicide”, with 450 suicides amongst construction workers in 2016 alone (The Guardian, 2019) and 26% of the workforce considering suicide in 2019 (CIOB, 2020).
I have gone on to read that contributing factors include being away from home (weekly commuting), the physically demanding nature of being on site, financial pressures and job security. Many of these pressures exist in the military so what’s different?
I think there are two key factors. Firstly, and most obviously all service personnel are salaried and so job security is not a concern. Whilst there is a definite and enforced Chain of Command this enables unacceptable behaviour by superiors to be challenged without risk of losing your job. There is also a strictly enforced discipline process to correct behaviours and a complaints process open to all. I have read that 21% of construction workers experienced bulling in 2021 (HSM, 2021). In my opinion the PM for my section is a bully. He will forcefully bully those he is able to into agreeing with him, and is very derogatory towards those he does not agree with or respect. Most worryingly he received a company award at last month’s summer function for “the person who always delivers results”. Whilst he certainly delivers I wonder at what cost in the long term?
Secondly, there is a welfare support network available to every soldier. Firstly, through the chain of command, with Army wide policies on mental health and welfare as well as unit policies for management and implementation. Service personnel also have access to support independently through the welfare department within each unit in addition to a plethora of service charities. This is not the case for most construction workers with the CIOB finding that “56% of construction professionals work for organisations with no policies on mental health in the workplace” CIOB, 2020). I have not been able to find any policy produced by the contractor I’m attached to (and am yet to find anyone in the company who’s ever seen one for a contractor they have worked for in the past).
Feeling insecure or unable to raise concerns, and having nowhere to turn to when struggling to cope is seemingly proving to be a fatal combination for construction workers.
Is what I’m witnessing an exception or a sad industry norm? I am curious to know what other people are experiencing on site? Do your companies have policies on mental health? Are people you work with confident / feel secure enough to call out unacceptable behaviours?
References:
https://www.theguardian.com/society/2019/aug/13/why-do-so-many-construction-workers-kill-themselves
https://www.hsmsearch.com/Survey-reveals-impact-bullying-construction
Temporary works design: An elongated, subcontracted solution
I’m currently working within a joint venture, in which either organisation usually take a risk-based approach to temporary works design (i.e. degree of risk dictates sign-off from a particular qualification with a certain number of years experience in temporary works design). The project I am on is similar but an early agreement with the client, within the project scope requirements, has adopted a notion supporting that all works with a risk categorisation of 1H or above (anything scoring in the high region below) requires sign off from a party external to the project (Client’s nominated authority) at the preliminary design and certified design and must be designed by a party external to the joint venture.
Within our temporary works design department (employed by the project), there are 5 personnel. Two of these have senior levels of expertise in temporary works design and corresponding qualifications (Chartered Professional Engineers). Within the project, all temporary works are classed as one of the ‘seven safety essentials’, which incurs a mandatory procedural approach to works, inviting more scrutiny than some less dangerous works (which I think is completely reasonable given the number of industry accidents relating to failure of temporary works making up around a third (Dobie et al. 2019)).
However, this does present a challenge to the construction team; as all works which I have come across so far (even those noted a risk category 1) have been designed and verified (as in permit to loads / platform certificates) by an external designer, which naturally incurs an additional time and financial burden. There seems to be two main designers who tender packages, both of which appear to be conservative (even within an area littered with previous GIs and their own previous designs, but that’s another story). The most evident case of this being a crane pad requirement for a double Franna crane lift (mobile cranes with notably small bearing area) of some Freyssinet gantry crane equipment (heaviest lift of 23t leading to relatively high bearing pressure (213kPa) but small zone of influence below surface due to small B). There is an existing 150mm asphalt surface (with c. 500mm crushed rock subgrade and then very compressive silt below). A previous designer (who left the project due to C-19 but was renowned for costing more but being worth every penny due to his efficiency in design) stated no need for a crane pad when the elements were craned in to place (successfully) but the current designer is stating 350mm minimum crane pad (as per their hand calculations using BR 470 – which by my understanding dictates a minimum thickness of 300mm for heavy plant anyway) with the mechanism of failure pertaining to punching shear in the weaker silt stratum below the fill.
We have since (due to the lift requirements changing), changed the lift study for a 250t crane (greater zone of influence but less kPa). This has resulted in a 117 kPa ground bearing pressure (factored load with 16m radius limit applied) and have now had to increase the pad to 400mm minimum (which counterintuitively appears more reasonable due to greater zone of influence and creating distance to poor silt stratum).
There are noted policy and contract-driven reasons for the need on our project to subcontract out Temporary Works. I’d be keen to hear 1) If work is being subcontracted out, do people feel they are getting bang for their buck in terms of the risks taken by the subcontracted designer and 2) Is anyone designing and getting designs signed off in-house for their Temporary Works? If so, what sort of time and cost impact this had (number of people and hours to design and deliver). We currently experience around 8-10 weeks for certified design from submission of a Temporary Works Design Brief and varying costs (but most recently quoted c. $30k for design of 20no piling pads).
References:
- Davies, M. (2017) Design of granular working platforms for construction plant – A guide to good practice. Temporary Works Forum. Accessed on 01/05/22. Available at: <https://myice.ice.org.uk/ICEDevelopmentWebPortal/media/Documents/Regions/UK%20Regions/IGS_YGG-Working-Platforms-1705.pdf>
- Dobie, M., Lees, A. Buckley, J. & Bhavsar, R. (2019) Working platforms for tracked plant – BR 470 guideline and a revised approach to stabilisation design with multiaxial hexagonal geogrids. International Society for Soil Mechanics and Geotechnical Engineering. Accessed on 02/05/22. Available at: <https://www.issmge.org/uploads/publications/89/71/13ANZ_110.pdf>
Subbies – Better the devil you know?
We have an on-site dilemma in sub-contractor management and wondering if anyone has similar experiences or tips in the management of under-performing subcontractors.
A civils works contractor was awarded the subcontract for the installation of the stormwater pits and drains across a new inner-city road scheme as a $3.5mil AUD lump-sum contract. The tender process was completed prior to my arrival on-site but I’ve been told they were awarded the contract as the cheapest tender as well as on the approved subcontractor list as an ex-employee of one of the parent companies on the JV.
Currently, 10% of the work is complete, 3 months behind on a 12-month programme. A litany of issues including formwork blow-outs and poor workmanship leading to non-conformance reports and re-works are already 3 times the value of the whole contract retention. When I posed the question if the JV should cut its losses early and find a new subbie, the response, from middle management, was to propose a site engineer manage this subbie full-time. The engineering team is already undermanned, with an extra engineer to look after this subbie at least 3 months away.
It is often easier to progress with the status-quo because it is more straightforward to deal with the problems in front of you than try and challenge the underlying issues. Everyone on site is already busy, and taking the time to re-tender would eat into project overheads, therefore the commercial management direction is to treat the known risk with supervision instead of terminating and engaging a less risky contractor. From an outside perspective, this feels very short-sighted but shows the monthly cash flow commercial drivers of the project outweigh the quality and customer satisfaction considerations at this stage of the project.
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