Volume change response and fabric evolution of granular MX80 bentonite along different hydro-mechanical stress paths

Despite the increasing understanding of bentonite behaviour, there is still missing evidence on how different hydro-mechanical loadings, including sequences of hydration and compression, affect the fabric and the volume change behaviour of the material. It is generally assumed that the interplay between the behaviour of clay assemblages and the overall fabric of the material is the reason of having final states that are dependent on the stress path followed. Here the results of an experimental campaign aiming to study these factors are reported and discussed. Free swelling and swelling pressure tests were performed, both followed by compression to a relatively high stress. The experimental program involved various samples that were dismantled at intermediate states in order to perform microstructural observations by means of mercury intrusion porosimetry and electronic scanning microscopy. It was observed that while the void ratio at a given stress level depends on the stress path, subsequent compression led to a unique virgin compression line. The data obtained at the microscale gave further insight for an interpretation of the volume change behaviour observed at the macroscale, showing that at high stress the material tends to recover the same fabric regardless of the path to saturation

Liquidity and the drivers of search, due diligence and transaction times for UK commercial real estate investments

Trading commercial real estate involves a process of exchange that is costly and which occurs over an extended and uncertain period of time. This has consequences for the performance and risk of real estate investments. Most research on transaction times has occurred for residential rather than commercial real estate. We study the time taken to transact commercial real estate assets in the UK using a sample of 578 transactions over the period 2004 to 2013. We measure average time to transact from a buyer and seller perspective, distinguishing the search and due diligence phases of the process, and we conduct econometric analysis to explain variation in due diligence times between assets. The median time for purchase of real estate from introduction to completion was 104 days and the median time for sale from marketing to completion was 135 days. There is considerable variation around these times and results suggest that some of this variation is related to market state, type and quality of asset, and type of participants involved in the transaction. Our findings shed light on the drivers of liquidity at an individual asset level and can inform models that quantify the impact of uncertain time on market on real estate investment risk

Bentonite mechanical evolution – experimental work for the support of model development and validation

The objectives of the Beacon experimental studies are to provide input data and parameters for development and validation of models and to reduce uncertainties about conditions and phenomena influencing bentonite homogenisation. Both the homogenisation of an initially inhomogeneous bentonite system and the persistence or development of inhomogeneities in the bentonite system under various mechanical and hydraulic conditions are investigated. Eight experiment teams perform tests involving different bentonite materials and different hydraulic and mechanical boundary conditions. The experiments performed within Beacon address the hydro-mechanical behaviour of macroscopically homogeneous bentonite materials, (the influence of initial granulometry and of hydro-mechanical paths on the final properties of bentonite, constant load and constant volume tests on the Czech Cerny vrch bentonite), the issue of swelling into a limited void (experiments performed in constant volume cells partially filled with bentonite, at different scales and with different emphases), binary mixtures or artificial inhomogeneities (experiments using bentonite block/pellet or pellet/powder mixtures, and the influence of the degree of saturation on the shearing behaviour at a bentonite – steel interface. This report is the first Beacon WP4 deliverable on experimental work and presents the status at Beacon mid-term

Didymodon fallax

Bryophyte