HESYS

ENGINEERING EXPLAINED

From assumptions
to understanding.

Explore the engineering behind HESYS: the information you put in, the methods behind the assessment, and the results you can review.

01 / GROUND MOVEMENT

HESYS Settlement

Current development scope

Estimate the ground movement associated with a tunnel or trenchless installation, then examine how the result changes with the alignment, ground conditions and your assumptions.

What goes in

Alignment and cover, excavation diameter, assumed volume loss and settlement trough width. For the 2D finite element model, define ground layers, elastic stiffness, Mohr-Coulomb strength and dilation where selected, lining, mesh and construction stages.

How it works

The empirical approach represents the transverse settlement trough with a Gaussian curve. Volume loss sets its area; the width parameter distributes that movement across the ground. The separate 2D finite element model solves a dry plane-strain ground slice using elastic or Mohr-Coulomb soil.

What comes out

Settlement contours, vertical and horizontal movement, point probes and section plots. The current trial includes Excel, DXF, GeoJSON/KML and report-figure exports, plus a portable HESYS project file.

A closer look at the settlement calculation

For a simple Gaussian surface trough:

s(y) = smax exp[−y² / (2i²)]

y is the horizontal offset from the tunnel centreline, i is the trough width parameter and smax is the peak settlement. In the user-defined surface-width approach, i = Kz0, where z0 is depth to the tunnel axis and K is selected for the assessment.

smax = [VL × (πD² / 4)] / [√(2π) × i]

Use VL as a fraction (1% = 0.01), with D and i in metres to obtain settlement in metres. For the same volume loss, a wider trough has a lower peak. The model also provides cohesive-ground and clay subsurface width options; their applicability depends on the ground and assessment level.

Theory background: Mair & Taylor, Bored tunnelling in the urban environment (ISSMGE).

Understand the assessment boundary

Volume loss is an engineering input, not a prediction of the construction process. The FE trial supports dry elastic and Mohr-Coulomb plane strain, including plastic yielding. It does not model Hardening Soil, groundwater response or consolidation and is not independently design validated. Ground movement alone does not establish damage to a building or utility. Review parameter sensitivity, mesh and boundary effects, and project evidence before drawing a design conclusion.

See Settlement inputs, outputs and product images →

02 / SITE DELIVERY

HESYS Inspect

Document pilot / planned field workflow

Bring inspection evidence and project documents together so the engineering team can see what was checked, which requirements apply and what still needs attention.

What goes in

Inspection requirements, inspection and test plans (ITPs), controlled drawings and documents, site observations and supporting evidence. Residential engineering is included in the product scope.

How it works

An ITP connects a work activity to its acceptance criteria and required checks. Hold and witness points identify when inspection or review is needed. Document control helps the team work against the intended revision.

Intended outputs

Traceable inspection records, ITP evidence, document histories and a clear view of open actions. These are planned product outcomes; the release specification and available exports will be confirmed before launch.

Evidence supports a decision

A completed checklist does not automatically establish compliance. Acceptance criteria, competence, site judgement and the responsible engineer’s review remain essential.

Explore the Inspect document pilot →

03 / DIRECTIONAL DRILLING

HESYS HDD

Coming soon

Planned design tools for hydrofracture assessment, pullback forces and drilling torque.

Design information

Bore geometry, cover, ground and groundwater conditions, pipe properties, drilling-fluid assumptions and installation conditions.

Engineering approach

Assess drilling-fluid pressure against the ground’s resistance to fluid escape. Examine pullback demand from friction, buoyancy and bends, alongside torque demand associated with the drilling operation.

Intended outputs

Pressure, pullback and torque profiles, critical locations and comparisons between design assumptions. Calculation methods, material coverage and checks will be defined in the release specification.

Further reading: Plastics Pipe Institute Handbook, Chapter 12: Horizontal Directional Drilling provides background on PE pipe installation loads. Its material-specific guidance is not a statement of HESYS compliance.

Pressure is only part of the picture

An assessment of hydrofracture cannot rule out all inadvertent returns. Fissures, permeable layers and existing pathways can allow drilling fluid to escape; site investigation and construction monitoring inform the assessment.

04 / DIRECT PIPE

HESYS DP

Coming soon

A planned tool for understanding the thrust required to install a Direct Pipe pipeline.

Design information

Installation alignment, pipe dimensions, ground conditions and assumptions for ground contact and friction.

Engineering approach

Build up installation resistance along the route, considering the excavation face, pipe–ground interaction and alignment. Examine how changing friction assumptions affects the thrust demand.

Intended outputs

Thrust demand through the installation, governing stages and a record of assumptions for comparison with project-specific pipe and equipment limits.

Process background: Herrenknecht — Direct Pipe. HESYS DP is being developed independently by Howl Engineering.

05 / PIPE JACKING

HESYS PJ

Coming soon

Planned assessment of jacking thrust and the influence of lubrication on installation resistance.

Design information

Drive length and geometry, pipe dimensions, ground conditions, face resistance and the proposed lubrication assumptions.

Engineering approach

Jacking load combines face resistance with friction along the pipe string. Lubrication can reduce that friction, but its effectiveness depends on ground conditions and how it is applied and maintained.

Intended outputs

Jacking-force profiles, comparisons of lubrication scenarios and governing thrust demand for engineering review against pipe, joint and jacking-system capacities.

Theory background: Pipe Jacking Association — About pipe jacking.

BUILT ON ENGINEERING JUDGEMENT

Talk through
your application.

Tell us about your project, the question you need to answer and the outputs your team needs.

Ask an Engineer →