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Soil Load & Traffic Calculators

Professional soil bearing capacity, pavement design, root protection, and traffic loading tools for landscape architects. Calculate subgrade strength, permeable pavement load capacity, wheel load stress distribution, vehicular access over planted areas, and root protection zones for trees under paving.

Soil Properties
Auto from soil, editable
Applied Load
Ultimate Bearing Capacity (qu)
–
kPa
Net Bearing Capacity
–
kPa
Allowable Bearing Capacity
–
kPa
Applied Pressure
–
kPa
Factor of Safety Achieved
–
ratio
Minimum Foundation Area Required
–
m²
Settlement Estimate
–
qualitative
Safety & Compliance Status
Terzaghi bearing capacity equation (strip footing): qu = c×Nc + γ×Df×Nq + 0.5×γ×B×Nγ. For square/circular foundations, shape factors apply. Bearing capacity factors Nc, Nq, Nγ are functions of φ. Settlement is highly site-specific; this tool provides a qualitative indicator only — detailed settlement analysis requires geotechnical investigation per BS EN 1997-1.
Traffic & Design Life
Subgrade & Materials
Total Pavement Depth
–
mm
Design ESAL
–
loads
Structural Number SN
–
AASHTO
Surface Course Thickness
–
mm
Base Course Thickness
–
mm
Required Sub-base Thickness
–
mm
Layer Build-up
LayerMaterialThickness (mm)Notes
AASHTO 93: SN = Σ(aᵢ×Dᵢ) where aᵢ=layer coefficient, Dᵢ=thickness. CBR to MR (resilient modulus): MR (psi) ≈ CBR×1500. UK HA 104 bases sub-base depth on CBR and traffic load class. This tool provides indicative thicknesses — consult HA 104/HD 26 for adoptable highway design.
Wheel Load Parameters
Vertical Stress at Depth
–
kPa (Boussinesq)
Contact Area per Tyre
–
m²
Contact Radius
–
m
Lateral Stress at Depth
–
kPa
Root Impact Warning
Stress Isobar Profile
Depth (m)Vertical Stress (kPa)Lateral Stress (kPa)Root Risk
Boussinesq (1885): vertical stress σz = q × (1 – (z/√(r²+z²))³) for circular load of radius r and intensity q at depth z. For wheel loads, r = √(P/(π×q)). Root impact zone: stresses >100kPa within the RPA may cause soil compaction and root damage — use load-spreading platforms.
Paving System
Clogging factor — typically 0.5 for long-term design
Sub-base Storage Volume
–
m³
Effective Infiltration Rate
–
mm/hr
Time to Fill Sub-base
–
hrs
Drainage Drawdown Time
–
hrs
Annual Runoff Reduction
–
m³/yr
Surface Capacity vs Storm
SuDS Source Control
Tree Data
From tree survey
Proposed Works
Critical Root Zone (CRZ = 1.5×RPA)
–
m radius
RPA Radius (BS 5837)
–
m
RPA Area
–
m²
CRZ Area
–
m²
Max Allowable Load within RPZ
–
kPa
Recommended Platform Spec
–
description
Works within RPA Assessment
BS 5837:2012: RPA radius = 12 × stem diameter at 1.5m height. Method statement required for any works within RPA. CRZ = 1.5×RPA recommended as outer protection zone. Load-spreading platforms must distribute load to <20kN/m² at soil surface (typical 18mm steel plate + timber). All works within RPA should be supervised by a BS 5837 arborist.
Vehicle Requirements
Turning Bay Required
–
m×m approx
Min Turning Radius
–
m
Required Access Width
–
m
Gradient Acceptable
Gate Width Adequate
Fire Access Compliance
Swept Path AnalysisUse tracking software for complex sites
BS 5588 / Approved Document B (Fire): Fire appliance access routes ≥3.7m wide, ≤8% gradient, capable of supporting 17.7t. Turning circles based on manufacturer data — for complex sites use AutoTURN or MX Road software for accurate swept path analysis.

CalcType: Professional Soil Load & Traffic Design Solutions — This comprehensive soil load and traffic calculator suite is engineered to support evidence-based geotechnical design, pavement engineering, root protection, and vehicular access planning for landscape architects, civil engineers, and project teams. The Bearing Capacity module applies Terzaghi’s (1943) general bearing capacity equation with shape factors for strip, square, and rectangular foundations, aligned with BS 8004:2015 and Eurocode 7 (EN 1997-1). The Pavement Design module applies UK Highways England HD 26/06 / DMRB thickness design methodology using CBR-based subgrade strength and cumulative Equivalent Standard Axles (ESA), with reference to HA 74/07 for light traffic routes. The Wheel Load & Stress module calculates tyre contact area and vertical stress distribution using Boussinesq (1885) elastic theory for homogeneous semi-infinite media, as applied in pavement and foundation engineering practice. The Permeable Paving module follows CIRIA C753 (SuDS Manual) and BRE 365 guidance for infiltration-based permeable pavement design, including stormwater storage reservoir sizing. The Root Protection module applies BS 5837:2012 (Trees in Relation to Design, Demolition and Construction) for Root Protection Area (RPA) and Structural Root Zone (SRZ) calculation, with construction encroachment assessment. The Vehicle Access Zones module evaluates route width, headroom, gradient, and turning circle requirements against Approved Document B (Building Regulations 2010), BS 9999:2017, Manual for Streets 2 (MfS2), and local highway authority standards. Technical Disclaimer: All geotechnical calculations, pavement thicknesses, stress distributions, permeable paving designs, root protection assessments, and vehicular access dimensions provided by this calculator are intended for preliminary design and feasibility assessment only. They do not constitute a formal Geotechnical Design Report (GDR), Pavement Design Report, Arboricultural Impact Assessment (AIA), or Transport Statement for planning or regulatory submission. All final structural, geotechnical, and highway designs must be verified by a qualified geotechnical engineer (CEng / FGS), chartered civil engineer (CEng MICE), or registered arboriculturalist (RCA) as appropriate. CalcType assumes no liability for structural failure, pavement failure, tree damage, or planning non-compliance arising from the use of these estimation tools.