Reinforced soil wall JM2, väg 607 Hassellund: check of the calculation sheet

The design sheet for the geogrid-reinforced wall applies load factors but uses characteristic instead of design shear strength, contrary to Design Approach 3 under SS-EN 1997-1 with the Swedish national choices in TSFS 2018:57. Recalculated with design values, sliding and bearing capacity on the clay under the wall are not satisfied.

Beräkning_jordarmerad_mur_JM2_rev_B.xlsxWall JM2, km 2+340 to 2+410, retained height 4.5 mDesign approach 3, safety class 3Prepared 2026-11-05

Summary

External stability · GEO

Sliding and bearing capacity fail with design shear strength

The sheet uses cu,k = 55 kPa for the clay where the design value is 55 ÷ 1.5 = 36.7 kPa. The partial factors are entered in Indata!D30–D31, but no formula refers to them. With design values, utilisation rises from 0.60 to 1.33 for sliding and from 0.60 to 1.54 for bearing capacity (sheets Glidning and Bärförmåga).

The recalculation keeps the sheet's traffic load of 20 kPa, while TK Geo 13 gives 15 kPa for design with partial factors. The utilisation ratios must be verified by a geotechnical engineer before they are used.

Internal stability · reinforcement

The geogrid checks still pass, the top layer with little margin

The same error applies to the reinforced fill: φ′k = 38° instead of φ′d = 31.0°, which raises the earth pressure coefficient Ka from 0.238 to 0.320. Pull-out of the top layer goes from 0.39 to 0.86, and rupture of the lowest layer from 0.38 to 0.51.

The tie-back wedge method and the interaction coefficient 0.8 are the sheet's choices and should be reviewed by a geotechnical engineer.

Required change

Reinforcement length 3.6 m needs to be 4.5 m

With design values, all checks pass from L = 4.5 m (L/H = 1.0). Sliding passes from 4.2 m, and bearing capacity governs. An alternative is ground improvement under the wall, which changes cu and must be verified separately.

Return the sheet to the designer for correction before the construction documents are issued.

The 4.5 m follows from the same recalculation and must be verified by a geotechnical engineer.

Recalculation of the sheet

Switch between the sheet as submitted (characteristic shear strength) and the corrected calculation (design values, set M2 per TSFS 2018:57). Change the reinforcement length or the clay strength to see what is needed. Select a check to see the formula in the sheet and the correction.

Shear strength in the calculation
3.6 m
55 kPa
0Checks that fail
0Highest utilisation
0Shortest L where all checks pass
0Strength used: cu clay · φ′ reinforced fill

Section through the wall

Geogrid layers coloured by their highest utilisation. Hover or select a layer for its values.

Geogrid, utilisation ≤ 0.80 0.80–1.00 > 1.00 Active wedge Contact pressure qEd on B′

Checks

Utilisation Ed ÷ Rd, required ≤ 1.00. The thin mark shows the value in the other mode.

    Sources and method

    Sources

    • Beräkning_jordarmerad_mur_JM2_rev_B.xlsxDesign sheet under review: Indata, Jordtryck, Glidning, Bärförmåga, Excentricitet, Armering6 sheets
    • PM Geoteknik väg 607 Hassellund.pdfGeotechnical memo: characteristic values cu,k 55 kPa (clay, adjusted for liquid limit), φ′k for fills, p. 11–1224 pages
    • JM2_sektion_km_2+340-2+410.pdfSection drawing: retained height 4.5 m, L 3.6 m, 9 geogrid layers at 0.5 m, embedment 0.5 m1 sheet, A1
    • Produktblad_geonät_PET_80-30.pdfGeogrid data sheet: long-term design strength TD 35 kN/m after reduction factors, interaction coefficient 0.84 pages
    • TRVINFRA-00230 Geokonstruktion, dimensionering och utformningTrafikverket's requirements for geotechnical structures (replaces TK Geo 13), including traffic loads for geotechnical structures along roadsRequirement document
    • TSFS 2018:57, chapter 38 (Swedish national choices for SS-EN 1997-1)Design Approach 3 for retaining structures, partial factors set M2: γφ′ 1.3 on tan φ′, γcu 1.5Regulation

    Method

    1. All formulas in the sheet were traced back to their input cells. The partial factors γM in Indata!D30 (tan φ′, 1.3) and Indata!D31 (cu, 1.5) have no dependent cells.
    2. The sheet was rebuilt with its own inputs. With characteristic strength, all five utilisation ratios match the sheet's summary to two decimals, which confirms the model.
    3. The calculation was repeated with design values, Xd = Xk ÷ γM: tan φ′d = tan φ′k ÷ 1.3 and cu,d = cu,k ÷ 1.5. Load factors as in the sheet: soil 1.0, traffic 1.3, γd = 1.0 (set C).
    4. Earth pressure: Rankine on the vertical back of the reinforced block. Sliding: undrained, Rd = B′ · cu,d, traffic on the block not included. Bearing capacity: undrained, (π + 2) · cu,d · ic + q, with B′ = L − 2e (SS-EN 1997-1, annex D).
    5. Internal stability by the tie-back wedge method as in the sheet: rupture against TD, pull-out over the length behind the active wedge with interaction coefficient 0.8. The sheet treats the eccentricity check (e ≤ L/6) as a serviceability check with characteristic values. This is common practice rather than a limit set in SS-EN 1997-1, and the check was not recalculated.
    6. The reinforcement length was increased in steps of 0.1 m until all checks passed with design values.

    Assumptions and limits

    • The review covers the sheet's own checks. Overall stability (separate calculation), drained long-term conditions and settlement of the clay are not part of it.
    • The partial factors entered in the sheet match set M2 in TSFS 2018:57. Also confirm which edition of TRVINFRA-00230 applies to the contract.
    • The traffic load of 20 kPa with load factor 1.3 is the sheet's value and has been kept. TK Geo 13 gives 15 kPa for design with partial factors (short slip surfaces) and 20 kPa for design with characteristic values. The value should be checked against the current TRVINFRA-00230; a larger surcharge is not automatically conservative in every check.
    • The reinforcement length that is needed is an indication for the designer, not a new design. Ground improvement or a different foundation is an equal alternative.
    • The whole check is to be verified by a geotechnical engineer before it is used. That covers the sliding and bearing formulas (SS-EN 1997-1, annex D) and the utilisation ratios, the internal stability method with TD 35 kN/m and interaction coefficient 0.8, the load factors and γd = 1.0 in set C against TSFS 2018:57 chapter 4, and whether 15 kPa rather than 20 kPa applies to this wall. The text of the current TRVINFRA-00230 was not available for this review.