Loess exhibits high sensitivity to water, rendering it susceptible to strength loss and structural destruction under hydraulic effects of rainfall, irrigation and groundwater. As an emerging soil improvement technology, microbial induced carbonate precipitation (MICP) stands out for its cost-effectiveness, efficiency, and environmental sustainability. In this study, hydroxypropyl methylcellulose (HPMC) was innovatively introduced into the MICP process to improve the strength and water stability of loess, and a set of unconfined compressive strength (UCS), direct shear, laser particle size analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were conducted. The results show that HPMC-modified MICP is able to generate a novel structural matrix combining organic and inorganic elements, significantly enhancing the strength, stiffness, and ductility of loess. HPMC protects loess from water erosion by forming viscous membranes on the surfaces of soil particles and calcium carbonate crystals. Increasing HPMC content can augment membrane viscosity, which is conducive to stabilizing the loess structure, but it has the negative effect of reducing inter-particle friction through increasing membrane thickness. As the HPMC content increased to 0.6%, the strength loss of loess under high water content decreased. These findings are expected to provide critical support for the engineering application of HPMC-modified MICP in loess improvement.

Hydroxypropyl methylcellulose (HPMC) incorporated bio-composite films (unplasticized and plasticized) were prepared from pregelatinized maize starch/polyvinyl alcohol (PMS/PVA) blends by solution casting method. 10% boric acid (BA) was used as crosslinker. The physico-mechanical properties (tensile strength (TS), elongation at break (%EB), water solubility and moisture uptake) of the bio-composite films were studied. The thermo-chemical stability of the biofilms was studied by FT-IR, TGA and DSC analysis. TS, %EB, water solubility and moisture absorbency of 10% HPMC containing unplasticized films were found 38.1 MPa, 8.5%, 61% and 32.3%, respectively, however, the films were hard and brittle. On the contrary, TS, %EB, water solubility and moisture absorbency of 10% HPMC plasticized films were found 19.2 MPa, 28.5%, 62.2% and 57.3%. The biofilms exhibited relatively low water solubility and moisture uptake compared to higher HPMC containing composite. The thermo-chemical analysis revealed that the HPMC incorporated plasticized film was more thermally stable compared to pure PMS, PVA, HPMC and other bio composite films due to strong hydrogen bonding interaction with BA. The biodegradability of HPMC incorporated plasticized films was confirmed by soil burial test (anaerobic condition, RH 98%, 3 months). Therefore, the plasticized biofilm would be considered an alternative approach for biocompatible packaging material.

In geotechnical centrifuge modelling the use of a pore fluid having viscosity greater than distilled water is a well-established method to satisfy the scaling laws required to model by a single prototype both diffusion and dynamic phenomena. However, the use of a pore fluid different from distilled water might influence the physical and hydro-mechanical properties of this soil. To analyse these possible effects, the paper presents results of a quite comprehensive experimental study carried out on Pontida sandy clayey silt compacted using two different pore fluids, namely hydroxypropyl methylcellulose (HPMC) and distilled water, recently used for centrifuge modelling in Seriate (Italy). Comparing the optimum Proctor standard of both mixtures, it was found that for the soil tested the use of HPMC has little effect on strength and small strain behaviour but affects the Atterberg limits, the Proctor compaction curve, the soil compressibility, the soil-liquid retention curve and the hydraulic behaviour both in the saturated and in the unsaturated soil range. Beside discussing the above, the aim of the paper is also to present a possible laboratory testing strategy to detect the soil properties relevant to numerical simulation of the observed behaviour of model soil structures used in geotechnical centrifuge testing.