Temperature effects on carbon storage are controlled by soil stabilisation capacities

Physical and chemical stabilisation mechanisms are now known to play a critical role in controlling carbon (C) storage in mineral soils, leading to suggestions that climate warming-induced C losses may be lower than previously predicted. By analysing > 9,000 soil profiles, here we show that, overall, C storage declines strongly with mean annual temperature. However, the reduction in C storage with temperature was more than three times greater in coarse-textured soils, with limited capacities for stabilising organic matter, than in fine-textured soils with greater stabilisation capacities. This pattern was observed independently in cool and warm regions, and after accounting for potentially confounding factors (plant productivity, precipitation, aridity, cation exchange capacity, and pH). The results could not, however, be represented by an established Earth system model (ESM). We conclude that warming will promote substantial soil C losses, but ESMs may not be predicting these losses accurately or which stocks are most vulnerable.

Numerical Analysis of Soil Reinforcement using Geocell infilled with Quarry Dust Powder

Massive urbanisation and infrastructural development caused by the growing population have taken place during the last decades. This means that in a rapidly expanding world economy we are running out of land. This problem has led to the use of ground improvement techniques to enhance the usability of land masses that were once not considered suitable for the development of infrastructure. Geocell is an innovative soil stabilisation product for civil engineering and development of infrastructures. They are cell containment systems which have been produced as an easy and durable material to stabilise and protect the compaction of the soil. The environmental concern regarding the disposability of quarry dust powder (QDP), produced from production units of M-sand (Manufactured sand), is of concern to the environment. The statement that is “waste of one industry should become the raw material for another” and that drawback can be addressed effectively by using it to improve the geotechnical characteristics of the weak soil. The purpose of this study is to find the optimal geocell-layer geometry and optimum combination of QDP infills to produce less settlement at a particular load using PLAXIS 2D software. The characteristics that have been varied are quarry dust powder in infill, geocell material and frequency of loading. These parameters were used for simulations to study the response of load vs settlements and the FOS of the slope. The FOS on the slope on the terrain was found to be 4.5, a steady slope. An optimised reinforcing mattress was ultimately found out.

Experimental Study on Stabilisation of Clayey Soil Using Cement and Bagasse Ash

In order for the foundation of building to be strong, the soil around it plays a critical role. So, researcher or engineer should have thorough knowledge about the factors affecting behaviour of soil which can be altered by the process of soil stabilisation. This study aims to investigate the applicability of SCBA (Sugarcane Bagasse Ash) to stabilize the clayey soil. Sugar factories produce waste after extraction of sugarcane gets brunt and the ash, hence produced is known as bagasse ash. Soil is treated with partial replacement of cement (3%, 6%, 9% and 12%) and with bagasse ash (2%, 4%, 6%and 8%). A total of 45 specimens were prepared in this study. Later those test specimens were evaluated for compaction properties. The results found after thorough study was that there was increase in the compaction properties with percentage increase in Sugarcane Bagasse Ash up to certain limit.

Feasibility of Using Nanosilanes in a New Hybrid Stabilised Soil Solution in Rural and Low-Volume Roads

The application of new materials for soil stabilisation is a growing field of study in recent years. In this work, the effect of two types of silica-based nanomaterials combined with binders (quicklime and cement) are studied to stabilise soils and form structural layers for rural and low volume roads. The physical and chemical properties of the materials have been determined, as well as the mechanical behaviour of the stabilised soil. Three hybrid stabilised soil sections have been designed using a multilayer elastic model, executed at full scale and measuring the evolution of their properties in the medium to short term. The results show that the application of silica-based nanomaterials and two types of binders on the tread layers provide high structural stability and good behaviour of the sections.

Performance of soils enhanced with eco-friendly biopolymers in unconfined compression strength tests and fatigue loading tests

Recently, biopolymers have emerged in soil stabilisation. The efficiency of biopolymers in groundimprovement is mainly dependent on biopolymer types, soil types, biopolymer contents, curing periods,thermal treatment and mixing methods. However, the effect of the initial moisture content during samplepreparation stages, on the mechanical behaviours of biopolymer-treated soils, has not been fullyunderstood. The first part of this study probed the role of initial moisture content, in treating Shanghaiclay with the xanthan gum by performing standard proctor compaction tests, Atterberg limit tests,unconfined compression strength (UCS) tests and microstructural analysis, while the second part contributedto capture the fatigue behaviours of the samples treated with an ideal moisture content by performingconstant-amplitude and stepping-amplitude fatigue loading tests. Our results showed that theimprovement appeared to occur from an average optimum moisture content for the treated soils (treatedoptimum), which was 3% wet of the untreated optimum. As the initial moisture content increased, theUCS values were elevated. However, there existed an ideal initial moisture content leading to the maximumstrengthening efficiency. For xanthan gum content (i.e., the mass of xanthan gum with respect tothe mass of dry soil) ranging from 1.0% to 5.0%, this ideal value was between 1.1 and 1.2 times the treatedoptimum. Our results also indicated that xanthan gum, as a biopolymer soil strengthener, was efficient inincreasing either fatigue life or bearing capacity, under repeated loading for xanthan gum-soil matrices,when compared to untreated soils. While the untreated soils failed at the stress level of only half the UCS,the xanthan gum-treated soils with a 3.0% xanthan gum content sustained at the end of the tests. Thesedata imply the potential use of xanthan gum in soil stabilisation, under repeated loads.

Engineering Properties of Sandy soil Improvement with Bacillus Simplex

Purpose: Stabilization of weak soil can be achieved through different methods, some of which include: jet column, cement stabilization and fly ash stabilization. Unfortunately, the use of the aforementioned methods of soil improvement affects the environment negatively thereby leading to environmental degradation. With the aforesaid impediment in mind, the need for devising methods of weak soil improvement becomes pertinent. Methods: Bacillus sp. - a non-pathogenic organism found abundantly in soil - was investigated in this study as a potential agent of soil improvement. The usability of Bacillus sp. in soil improvement was investigated with direct shear tests and permeability tests under optimum conditions in this study.Result: Time-dependent study on the effect of the ureolytic bacteria Bacillus simplex induced calcium carbonate precipitation shows reduction in permeability and increase in the strength of the soil under study. On exhaustion of the available nutrients in the soil however, the strength of the soil is not negatively impacted.Conclusion: Microbially induced calcium precipitation by Bacillus sp. is effective in soil improvement as such it may serve as substitute for conventional soil stabilisation techniques. The ability of the bacteria to precipitate calcium carbonate in the soil leads to reduction in the permeability and increase in the shear strength of the soil.