Welcome to the May 2025 issue of Ground Improvement (Vol 178, Issue 2). Ground Improvement has seen significant expansion and application in ground engineering projects globally over the last 20–25 years. This is reflected in the recent second-generation Eurocode 7 Geotechnical design codes. Whilst a number of geotechnical processes were covered in the first-generation Eurocode 7 (BSI, 2004), ground improvement was only allocated a 1 page sub-section within a section entitled ‘Fill, dewatering, ground improvement and reinforcement.’ This compared with pile foundations which was allocated 18 pages of the code. During preparation of the second-generation Eurocode 7, it was recognised that ground improvement had advanced since 2004 and hence it was considered necessary to significantly improve ground improvement coverage. This is discussed further by Essler and Serridge (2025).
This issue features seven articles comprising six general papers and one briefing paper. Their content highlights recent developments and advancements in ground improvement, as well as the diverse range of ground improvement techniques and their global reach. The first three papers capture recent ground improvement research from India. In the first paper, Madhira and Kota (2025) investigate the response of geosynthetic-reinforced beds to loading. Whilst reinforced foundations beds (RFB) are highlighted as having been found to be effective in improving the response of foundations and pavements in the context of relatively soft subgrades, the authors note that an approach for estimating the degree of improvement with RFB is lacking, particularly with regard to modulus of deformation or stiffness. The authors present what they describe as a new and simple method for the estimation of modulus of deformation of RFB, based on measured stresses at the reinforcement-soil interface or below. The versatility of the method in estimating the modular ratio of the RFB is illustrated by analysis of test results from the existing literature. The authors consider the approach will help practitioners to estimate the foundation settlements by treating RFB as a two-layer system and utilising the corresponding elastic solutions.
In the second paper Bishnoi et al. (2025) address the concept of incorporation of a geofoam compressible inclusion, between a retaining structure and backfill, to significantly reduce lateral pressure. The authors highlight the importance of field scale investigation to build on the previous largely laboratory and numerical based studies. Parametric tests are undertaken on an instrumented 6 metre high concrete cantilever wall, in the field, to measure earth pressure, wall deflection and geofoam (expanded polystyrene (EPS)) compression during backfilling. Three combinations of geofoam density and thickness are used and the results compared with a control test without any geofoam inclusion. A developed numerical model is then validated with the field scale test results to determine pressure variation for the different combination cases. The compressive strains generated in EPS, irrespective of density and thickness is found to exceed the design strains of previous studies, with the majority of strains found to be due to compaction, which the authors highlight is not considered in earlier studies. Further research is indicated as being required to re-evaluate the design compressive strain limit in EPS by consideration of compaction efforts that are realised in the field, also the effect of traffic loading on EPS response.
AR et al. (2025) investigate the effects of sulfate content on long term strength reduction of lime-stabilised marine clay in the third paper. For the purposes of the research, 6% lime and 4% sulfate is mixed with Cochin Clay, with unconfined compressive strength (UCS) of the clay found to increase for the first 3 months, followed by a gradual decline leading to a 36% reduction in strength after 2 years from the peak strength observed at 3 months. To assess its effect in counteracting the negative impact of the sulfate content on stabilisation strength, the addition of barium hydroxide is then investigated. Both a pure laboratory grade product and a commercial product are investigated. Whilst both products contribute to a consistent increase in shear strength of the stabilised clay, twice the pre-determined dosage of the commercial product is required, to exceed the performance of the pure laboratory grade product. However, the significant cost difference between the two products is highlighted by the authors as making the commercial product economically more viable despite the high dosage requirement. Scanning electron microscope (SEM) results show consistency with the strength behaviour, further validated by x-ray diffraction (XRD) analysis.
Continuing the soil stabilisation theme, the fourth paper from China, by Chen et al. (2025), investigates the modification of red clay properties by incorporation of a calcium carbonate admixture. The clay, from Guilin, Guangxi, is characterised by high natural moisture content, liquid limit and plasticity. The effects of different forms and content of calcium carbonate, incorporated as an admixture, termed heavy calcium carbonate (HCC), (essentially crushed carbonate rock), and light calcium carbonate (LCC), (the precipitate produced from the chemical reaction between hydrated lime and CO2), respectively are investigated through, unconfined compressive strength (UCS) testing (including failure mode modification), scanning electron microscope (SEM) and low-field nuclear magnetic resonance (NMR) analysis, together with bulk density measurements. The introduction of calcium carbonate is shown to lead to an increase in micropores, disrupting the original soil structure. In terms of the overall improvement effects, a 5% concentration of HCC is determined to be optimal and increases the maximum dry density.
In the fifth paper Dias et al. (2025) present the results of research from Thailand, investigating the behaviour of a lattice frame reinforced (LFR) system under (coastal) rock embankments and which are employed as settlement reducing ground improvement. The system comprises two components, a mortar injected polyester tube lattice frame (LFR mortar tube) and an underlying polyester sheet (LFR sheet). Two experimental embankments employing the system are constructed for the purposes of the study with soil settlement under the embankments monitored for a period of 30 months. The paper then aims to explain the mechanisms of the LFR system, by applying finite element simulations and the field measurements, and with tension-stiffening effects incorporated for modelling the behaviour of the LFR mortar tube. The analysis and monitoring show that the LFR system could effectively reduce the long-term soil settlement caused by the embankment(s). The FE analysis shows that the mortar tubes behaved as tensile members and the grid spacing of the LFR mortar tube had a significant effect on settlement reduction. The gathered field measurements can be satisfactorily simulated using FE analysis by considering the tension-stiffening behaviour.
In the sixth paper, also from Thailand, and continuing the ground consolidation theme, Koslanant et al. (2025) propose two novel curve fitting observational methods for prediction of radial consolidation settlement (and ultimate settlement), employing computational analysis with interative optimisation algorithms and numerical integration for what are described as methods 1 and 2 respectively, to fit the Barron’s radial consolidation curve using the least square analysis concept. Verification of the accuracy of both proposed methods is established using test results from the constant rate of strain consolidometer (with radial drainage) (CRS-R) and field monitoring data (from a prefabricated vertical (band) drain project). The results show that the Method 1 approach provides the highest accuracy when compared to the Asoka method and proposed method 2. All predicted curves plotted using the proposed methods are shown to have an excellent fit with a coefficient of determination, R-squared >0.99. The proposed methods are considered by the authors as simple to apply.
Finally, the Briefing paper from the UK, by Essler and Serridge (2025), provide some insight into ground improvement coverage in the second generation Eurocode 7, covering geotechnical design in Europe and other countries outside Europe. The code consists of three main parts, with Ground Improvement covered in Part 3 (Geotechnical Structures), Clause 12. Two forms of ground improvement are defined — discrete ground improvement and diffused ground improvement. The authors note that the new EN 1997 Parts 1–3 provide a very detailed methodology for the design of ground improvement and consider this should lead to a more defined design environment where individual designers must comply with basic rules and therefore risk is formalised. It is also highlighted that the structure of Part 3 provides flexibility to permit new ground improvement techniques to be accommodated in the future. Publication of BS EN 1997-3 (Part 3) is expected during the first half of 2025.
I trust you will find these papers interesting and informative. Written discussion on the papers is encouraged to further enhance their research contribution. Details on how you can contribute are provided on the journal website https://icevirtuallibrary.com.toc/jgrim/current. The journal would also encourage submission of papers documenting case histories of ground improvement application from practitioners.
Finally I would like to thank the authors, reviewers, editorial panel members and Emerald Publishing staff, who have contributed to the May 2025 issue of the Ground Improvement journal.
