Tony Gould's Technical Blog

A Contemporary review of the use of modular hydraulic propping systems for the temporary support of deep excavations.  
 

Firstly, apologies for plagiarising and modifying the post WW2 “export or die” slogan which was generally associated with the motor industry, in the days that we had we actually had one, and the need for foreign money to keep Britain afloat. However, in this fast paced digital age, I can’t help feeling that the principal of the adage applies as strongly now as back then.

Hello and welcome back to the drawing board with me, Steven Lloyd. A few months ago I talked to you about the design of hydraulic struts and I mentioned that at the end of the strut there’s always this hydraulic unit now the reason it's there is so you can pump some fluid in and adjust the length of the props so they will always meet the size requirements.

Today we are going to take a look inside the hydraulic cylinder and see how that works. I’m going to start simple talking about single acting cylinder. This basically means that you can pump it out but you can’t pump it back in, strictly speaking.

Once again welcome back to the drawing board. In the last couple of videos we talked about the design of equipment and the resistances of that equipment. We looked at the props and we looked at the wailers. Now we will have a look a bit at the other side, where the forces come from. 

Welcome back to the drawing board and today are we talking about the design of walers as well as the combined effects that act upon them.  When I say combined effects I’m talking about axial force, bending moment and shear forces all acting on the waler at the same time. I won’t be talking about torsion because you don't usually see torsional effects on the kind of walers that we do. 

Welcome to the very first “Back to the Drawing Board” with Steve Lloyd at Groundforce Shorco technical offices in Leeds. Today Steve will be explaining how we design our hydraulic props and the kind of actions and effects that act upon it.

It’s been a while since we’ve had a real nuts and bolts engineering entry in the blog and thanks to Mr. Garford-Tull for providing some comments to previous blog entries. I’ve been inspired to write a technical entry about a few of the more complex issues surrounding thermal effects.

Well summer has been and gone and judging from the persistent fog hanging around for the last couple of days, we must be well in to Autumn. Two of my colleagues are over in Sydney this week providing technical training for our Australian partner Coates Rental; I am hoping that they have not thrown away the return portion of their ticket!

 Following on from an earlier entry about the humble road plate, I thought I’d make a showcase of the often abused, manhole shutter. It may seem like a simple, primitive piece of equipment but even these simple tools have a raft of technical data and calculations to back them.

Considering that the shutter is, for the most part, just a 2mm thick sheet of steel, they are deceptively strong. This is primarily down to the way in which they carry the load from the fresh concrete within. 

For what now seems like an age, we have been operating a load monitoring service with pre-calibrated electronic swivel pins to measure the force acting within a hydraulic prop. An important part of this system is the test rig that we use to calibrate the load cells.

Returning this month to a more technical theme I have unashamedly plagiarised one of my colleague’s recent technical notes concerning the long serving (and suffering) trench crossing plate. These are one of the less glamorous pieces of kit in our hire fleet generally cut out of old ¾” thick boiler plate in 8’ x 4’ (apologies for the imperial units) size. To comply with current safety regulations they are generally coated with some sort of non-slip or anti-skid coating with a lifting hole burnt into each corner; and that is just about as sophisticated as they get.

Once again I have managed to embarrass myself in that this is the first time I have posted in 2015. January and February have vanished already and here we are getting on for a quarter of the way through the year already. Anyway let me bring you up to speed with what has been going on in the technical department over the last couple of months.

It’s difficult to believe that the end of another year is fast approaching. I thought that this was an ageist thing but talking with the guys in the office, everyone seems to feels the same. As usual the festive season gives us chance to reflect on the year departing and look forward at the same time. 2014 has been another good if challenging year for both Groundforce and the technical team, highlights include, in no particular order.

Firstly, rather sheepish apologies for not posting a blog since September. Today’s 11/11 date seems an appropriate day for me to commit pen to paper again so to speak, as apart from the more obvious and poignant anniversary remembered on this day, it is also the date I started out in the shoring industry, way back in 1985. 

After a bit of a summer break its time to put pen to paper again on the technical aspects of shoring equipment. The last two blogs have focused on trench box design, so to complete the picture; I will go through the basic design principals of the increasingly popular rolling strut box and slide rail products that we supply.

Struts or spindles as they are sometimes known perform the understated but essential task of transmitting the forces exerted by the ground between opposing box plates.

One of the many projects we are desperately trying to complete at present is the launch of our new technical file. Whilst drafting out some guidelines relating to the design of trench boxes, it struck me that this would make an ideal technical yet easy going blog submission.

More and more engineers are turning these days towards computer numeric modelling and FEA. I have to admit that I am a bit ambivalent about it all. On the one hand, these are powerful tools capable of modelling complex scenarios and achieve incredibly accurate results in rapid timescale.

Prior to the adoption of Eurocodes in the UK, all the load capacity verifications and charts for our standard CHS struts were determined from BS 5950; EC3 although on the face of it, being a limit state code, is a natural progression from BS5950 however numerous detail changes exist within the document. 

For many years, Groundforce has been supporting young engineers by providing employment, training and education in many forms. Over the last five years in particular, we have sponsored a steady stream of budding engineers through university on a part time basis.

Following on from last month’s blog regarding preparations for the annual Ground Engineering Basement Conference; now this has been and gone and the dust settled, perhaps it is time to reflect on the event and to assess whether it has all been worthwhile.

After the summer’s “blog holiday” I am pleased put pen to paper again so to speak and report on our preparation for our headline marketing event; that is Ground Engineering’s Sixth Annual Basements and Underground Structures Conference; which is incredibly and rather worryingly less than a week away. 

In April’s technical blog I touched upon some of the basic principles of BIM and then started to look at what this could mean for our industry in general. 

When groundwater is likely to be encountered within and below an excavation, this generally means bad news for the designer at least due to a number of undesirable effects, including increased loads on supports, flow of material, boiling (see photo opposite) or heave of the formation etc.

This month I thought I would add a small introductory piece of the very topical subject of Building Information Modelling otherwise known as BIM. Grateful thanks to my colleague Dan Cuthbert for penning this blog.

British standards may come and go as do the latest industry trends and buzz words but how much has really changed in shoring in recent years? 

Apologies once again for not posting for a while; the best laid plans and all that. At least it’s good to be busy, or so they say! 2013 has already seen quite a few changes to the Groundforce Technical Department. A makeover of our main office, which has been looking a bit tired of late, has just been completed. 

An unusually treacherous journey into work this morning reminds me that yet another year has flown by and the well earned and looked-forward to Christmas break is fast approaching.

Apologies for not posting for a while, poor excuse I know but the months just seem to fly by. For something a bit different from my usual offering, I have asked one of my technical colleagues Helen Aird to put something together along the lines of “a day in the life of a Technical Sales Engineer”. 

After the brain ache sessions of the last two months blogging on thermal effects in struts, I thought it better to provide perhaps a gentler themed blog commensurate with the holiday season being in full swing. 

Last month we looked at the basic theory behind calculating thermally induced load effects in steel props. This month we’re going to attempt to bring this more into Groundforce’s arena by applying these theories to one of our modular hydraulically operated props.

Continuing last month’s technical theme, this month’s blog discusses another old chestnut; the effect of ambient temperature change (thermal effects) on hydraulic struts. 

Why do we so often apply the 45° rule of thumb for the influence that surcharges have on the design of excavation support?

Apologies for not posting for a while but an exceptionally busy end of year placed great demands on the technical team. It’s nice to be busy or so they say!

With a welcomed boost in activity over recent weeks, I thought this month we would give you a whistle-stop update into what is going on within Groundforce`s European adventure, an overview of some of the projects we are working on at the minute and even show you some pictures of our equipment in the ground.

For those of you who have been on tenterhooks since the basic principals of hydraulic struts entry back in March, your wait is finally over as in this edition I intend to take it one step further and delve into more advanced workings of hydraulic struts.

Firstly apologies for not submitting a blog entry for a while, must be a sign of my age but the months seem to fly by particularly when you have to compile a monthly departmental report! 

I know last month’s entry promised you more on the principals of hydraulic struts, however there has been so much going on in the technical camp since my last transmission that I thought it might be preferable to hear about that instead……. so you’re just going to have to wait a little longer before we get back on with the joys of pre-stress!

I thought that this month I would take the opportunity to go back to basics and give a brief insight into how Groundforce propriety equipment operates and to try and explain what is actually going on within the struts when you get to work on the hand pump, or when you simply flick the lever on the labour saving motorised pump.

After a well deserved festive week off, followed by the usual slow first week back, construction sites are starting to make noises again and 2011 is underway, and at pace!

As the end of year fast approaches and the wind-down begins in earnest (hope the MD does not read this!), there is a definite change in the mood of the camp here in the technical department; the telephones ring less often, the number of new projects starts to dwindle, staff rush to use up their remaining holiday entitlement and the seemingly never ending supply of sweets and cake from kind suppliers becomes available.

Value engineering (VE) is a current buzz phrases within the industry. It is a systematic process which either identifies and eliminates unnecessary costs or increases utilisation.

The latest development in proprietary support systems is the ability to equip struts with integrated wireless load monitoring capability. 

The initials “SWL” are one of the most easily recognised and understood acronyms in the construction industry; you know that something marked “SWL 5 Tonnes” can safely support a maximum load of 5 tonnes in real terms.