RJM GROUND SOLUTIONS LIMITED

value driven geotechnics by design

PLAXIS 2D Version 9.0 purchased

In order to be able to provide the very latest in sophisticated finite element analysis (FEA) to our clients we have recently invested in a licence for PLAXIS 2D version 9.0.  PLAXIS is widely regarded in the geotechnical industry as the state of the art software for numerical modelling of soil behaviour and soil structure interaction. 

PLAXIS has the ability to use a wide range of constitutive models from the simple Mohr Coulomb model for routine analysis to a range of sophisticated models including a soft soil creep model which allows the time-dependent and logarithmic compression behavior of normally consolidated soft soils to be simulated.  In addition PLAXIS allows steady state seepage analysis of ground water flow to be determined and for special applications we are able carry out transient modelling of ground water flow using the PLAXFLOW extension to PLAXIS.

As part of our investment in our advanced numerical modelling capability we are working with WILDE FEA, the UK distributor of PLAXIS, to become one of their associate partners allowing our experience using PLAXIS to be shared with other users and encouraging the wider use of FEA in geotechnical design.

Whilst an extremely powerful tool capable of sophisticated analysis, simple models can be set up as quickly as with any other geotechnical software.  This allows us with a single computer model to determine safe bearing pressures, stable slope angles, ground settlement, and the stresses imposed upon structures.  The consequence for our clients is reduced design costs, less conservatism in design and ultimately a more economical product. 

Chalk Mine Stabilisation Presentations

Chris and John in conjunction with Andrew O'Donovan of Ritchies have been undertaking a series of presentations describing the holistic approach to chalk mine stabilisation applied at Briars Lane in Hatfield.  Presentations have been given to four regional groups of the ICE and Geological Society.  In addition a presentation was given to a joint meeting of over 100 members of the IMMM and BTS at the ICE headquarters in George Street.  All presentations were very well received and provided an opportunity for the important lessons learnt in this novel scheme to be shared with a wider audience.

A paper describing in more detail the methodologies and approaches used at Briars Lane is due for publication shortly in Ground Engineering.  Watch this space for more details.

RJM is providing geotechnical support for the stabilisation of a failing railway embankment.  Having completed a desk study of the site an initial phase of ground investigation was specified and supervised.  Careful examination of soil samples during this investigation identified a significant thickness of soliflucted material.  As a result a deep stabilisation solution was required and subsequently a second phase of investigation comprising rotary boreholes was carried out.  Due to access difficulties Ritchies' Sherpa slope climbing rig was used in conjunction with a rotary head - the first time that this arrangement had been used in the UK.

Devil's Bridge, Chapeltown

RJM is providing geotechnical support for the design of a new dam to attenuate storm flows entering a business park to the north of Sheffield.  Following a detailed desk study it was identified that the site had a considerable legacy of coal and ironstone mining beneath it which posed a significant risk to construction.  A multi purpose ground investigation was specified to address the mining risk, determine the stratigraphy and obtain soil and rock design design parameters.  In addition in situ packer (lugeon) testing was carried out to determine the soil and rock permeabilities.  This scheme is now moving towards detailed design in which RJM will be carrying out detailed seepage and stability analyses of the dam using finite element analysis software to determine the depth of cut off and dam cross section required.

RJM has provided geotechnical support in the investigation and design of remedial slope stabilisation measures for a railway rock cutting at the eastern entrance to Blea Moor tunnel.  Due to access difficulties investigation was limited to examination of rock exposures and hand dug pitting.  The stabilisation solution involved a combination of crest drainage, face netting, spot bolting and scaling.  RJM provided site supervision to control the extent of the scaling and bolting works and supervise the testing of and installation of the mesh and associated support system.

Broken Brae, Richmond

RJM has been working closely with developers to secure planning permission for a new ecological holiday park located on the northern banks of the River Swale.  The proposed development is sited below the 100 year flood level of the adjacent river and RJM were asked to assess the condition of the existing flood defences and provide advice on any remedial measures necessary.  Following an initial walk over survey an intrusive ground investigation was carried  using the services of our partner company Drift Ground Investigation.  The results of this study were then used to advise on the remedial measures necessary for the flood defences to provide adequate protection against the design flood event.  In addition the results of the investigation were used to provide foundation advice for the proposed lodges and the substantial earthworks operations proposed.

Close liaison was maintained with the Environment Agency throughout the scheme in order to ensure the information required for their approval was obtained.

Briars Lane, Hatfield

RJM have been working closely with both the client and contractor Ritchies on a £2.65M chalk mine infilling scheme in Hatfield.  The site was mined up until the early part of last century and surface subsidence has subsequently caused numerous problems to structures across the site including surface collapse adjacent to a single storey bungalow during the late 1990's.  The scheme is the first time that stabilisation of partially collapsed chalk mines has been undertaken in the UK and has presented a number of challenges.  RJM have been engaged as technical specialists to ensure an effective treatment methodology is developed.  The relatively straightforward process of bulk infilling open voids has been carried out using foamed concrete.

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Last modified: 03-08-09