How much land-based greenhouse gas mitigation can be achieved without compromising food security and environmental goals?

Feeding 9-10billion people by 2050 and preventing dangerous climate change are two of the greatest challenges facing humanity. Both challenges must be met while reducing the impact of land management on ecosystem services that deliver vital goods and services, and support human health and well-being. Few studies to date have considered the interactions between these challenges. In this study we briefly outline the challenges, review the supply- and demand-side climate mitigation potential available in the Agriculture, Forestry and Other Land Use AFOLU sector and options for delivering food security. We briefly outline some of the synergies and trade-offs afforded by mitigation practices, before presenting an assessment of the mitigation potential possible in the AFOLU sector under possible future scenarios in which demand-side measures codeliver to aid food security. We conclude that while supply-side mitigation measures, such as changes in land management, might either enhance or negatively impact food security, demand-side mitigation measures, such as reduced waste or demand for livestock products, should benefit both food security and greenhouse gas (GHG) mitigation. Demand-side measures offer a greater potential (1.5-15.6Gt CO2-eq. yr(-1)) in meeting both challenges than do supply-side measures (1.5-4.3Gt CO2-eq. yr(-1) at carbon prices between 20 and 100US$ tCO(2)-eq. yr(-1)), but given the enormity of challenges, all options need to be considered. Supply-side measures should be implemented immediately, focussing on those that allow the production of more agricultural product per unit of input. For demand-side measures, given the difficulties in their implementation and lag in their effectiveness, policy should be introduced quickly, and should aim to codeliver to other policy agenda, such as improving environmental quality or improving dietary health. These problems facing humanity in the 21st Century are extremely challenging, and policy that addresses multiple objectives is required now more than ever.

Vertical uplift resistance of two closely spaced horizontal strip anchors embedded in cohesive-frictional weightless medium

The vertical uplift resistance of two closely spaced horizontal strip plate anchors has been investigated by using lower and upper bound theorems of the limit analysis in combination with finite elements and linear optimization. The interference effect on uplift resistance of the two anchors is evaluated in terms of a nondimensional efficiency factor (eta(c)). The variation of eta(c) with changes in the clear spacing (S) between the two anchors has been established for different combinations of embedment ratio (H/B) and angle of internal friction of the soil (phi). An interference of the anchors leads to a continuous reduction in uplift resistance with a decrease in spacing between the anchors. The uplift resistance becomes a minimum when the two anchors are placed next to each other without any gap. The critical spacing (S-cr) between the two anchors required to eliminate the interference effect increases with an increase in the values of both H/B and phi. The value of S-cr was found to lie approximately in the range 0.65B-1.5B with H/B = 1 and 11B-14B with H/B = 7 for phi varying from 0 degrees to 30 degrees.

Target reliability-based optimisation for internal seismic stability of reinforced soil structures

In this paper, an approach for target component and system reliability-based design optimisation (RBDO) to evaluate safety for the internal seismic stability of geosynthetic-reinforced soil (GRS) structures is presented. Three modes of failure are considered: tension failure of the bottom-most layer of reinforcement, pullout failure of the topmost layer of reinforcement, and total pullout failure of all reinforcement layers. The analysis is performed by treating backfill properties, geometric and strength properties of reinforcement as random variables. The optimum number of reinforcement layers and optimum pullout length needed to maintain stability against tension failure, pullout failure and total pullout failure for different coefficients of variation of friction angle of the backfill, design strength of the reinforcement and horizontal seismic acceleration coefficients by targeting various system reliability indices are proposed. The results provide guidelines for the total length of reinforcement required, considering the variability of backfill as well as seismic coefficients. One illustrative example is presented to explain the evaluation of reliability for internal stability of reinforced soil structures using the proposed approach. In the second illustration (the stability of five walls), the Kushiro wall subjected to the Kushiro-Oki earthquake, the Seiken wall subjected to the Chiba-ken Toho-Oki earthquake, the Ta Kung wall subjected to the Ji-Ji earthquake, and the Gould and Valencia walls subjected to Northridge earthquake are re-examined.

Analytical model for stress-strain response of plastic waste mixed soil

Recycling plastic water bottles has become one of the major challenges world wide. The present study provides an approach for the use of plastic waste as reinforcement material in soil, which can be used for ground improvement, subbases, and subgrade preparation in road construction. The experimental results are presented in the form of stress-strain-pore water pressure response and compression paths. On the basis of experimental test results, it is observed that the strength of soil is improved and compressibility reduced significantly with the addition of a small percentage of plastic waste to the soil. In this paper, an analytical model is proposed to evaluate the response of plastic waste mixed soil. It is noted that the model captures the stress-strain and pore water pressure response of all percentages of plastic waste adequately. The paper also provides a comparative study of failure stress obtained from different published models and the proposed model, which are compared with experimental results. The improvement in strength attributable to the inclusion of plastic waste can be advantageously used in ground improvement projects.