The importance of applying unsaturated soil mechanics to geotechnical engineering design has been well understood However, the consumption of time and the necessity for a specific laboratory testing apparatus when measuring unsaturated soil properties have limited the application of unsaturated soil mechanics theories in practice Although methods for predicting unsaturated soil properties have been developed, the verification of these methods for a wide range of soil types is required in order to increase the confidence of practicing engineers in using these methods In this study, a new permeameter was developed to measure the hydraulic conductivity of unsaturated soils using the steady-state method and directly measured suction (negative pore-water pressure) values The apparatus is instrumented with two tensiometers for the direct measurement of suction during the tests The apparatus can be used to obtain the hydraulic conductivity function of sandy soil over a low suction range (0-10 kPa) Firstly, the repeatability of the unsaturated hydraulic conductivity measurement, using the new permeameter, was verified by conducting tests on two identical sandy soil specimens and obtaining similar results The hydraulic conductivity functions of the two sandy soils were then measured during the drying and wetting processes of the soils A significant hysteresis was observed when the hydraulic conductivity was plotted against the suction However, the hysteresis effects were not apparent when the conductivity was plotted against the volumetric water content Furthermore, the measured unsaturated hydraulic conductivity functions were compared with predictions using three different predictive methods that are widely incorporated into numerical software The results suggest that these predictive methods are capable of capturing the measured behavior with reasonable agreement

Laboratory measurement of hydraulic conductivity functions of two unsaturated sandy soils during drying and wetting processes

A review on fractal footprint of cement-based materials

The paper presents the results of the analysis of the thermal cracking patterns and fracture zone of microsilica-modified cement matrix made of the low-alkali cement. The material was subjected to a two-stage thermal load. To identify cracks an original, the image double-segmentation procedure, using machine learning algorithms was developed. To characterize the cracks structure, the fractal geometry was applied, measuring the fractal dimension of the cracking patterns. Moreover, the total crack area and the crack density were analyzed. In the case of the fracture line analysis the fractal dimension was examined in two variants. The applied parameters allowed to describe the complexity degree of the surface cracks structure. The process of development of thermal cracks caused by repeated thermal loading was also characterized. The obtained results showed strong correlation between the tensile strength, fractal dimension of the cracking pattern and crack density. Knowledge in this area allows to estimate mechanical properties of the cement matrix on the basis of measurement and evaluation of morphology of the thermal cracking patterns.

Fractal characterization of thermal cracking patterns and fracture zone in low-alkali cement matrix modified with microsilica

A DEM approach to study desiccation processes in slurry soils

Mechanical response of hydronic asphalt pavement under temperature–vehicle coupled load: A finite element simulation and accelerated pavement testing study

Load reduction on high-filled cut-and-cover tunnel using discrete element method

Alternative Hydronic Pavement Heating System using Deep Direct Use of Geothermal Hot Water

High-filled cut-and-cover tunnels (HFCCTs) can be used to reclaim usable land due to the unique landforms in western China. The load reduction methods used to reduce the earth pressure on ...

Coupled Effect of Expanded Polystyrene and Geogrid on Load Reduction for High-Filled Cut-and-Cover Tunnels Using the Discrete-Element Method

High-filled cut-and-cover tunnels (HFCCTs) are common in northwestern China because their construction allows usable land over the CCT to be reclaimed. However, due to the unique landforms...

Coupled Effect of Cross-Sectional Shape and Load Reduction on High-Filled Cut-and-Cover Tunnels Considering Soil–Structure Interaction

The high-filled cut-and-cover tunnel (HFCCT) is a solution to reclaim more useable lands due to the unique landforms of Loess Plateau in northwestern China. Because of the ultrahigh backfill, the estimation of vertical earth pressure will significantly affect the design and safety of the cut-and-cover tunnel (CCT). The current methods for estimating the vertical earth pressure are either to overestimate or underestimate the vertical earth pressure on the top of HFCCT. To more precisely estimate the vertical earth pressure distribution, the vertical earth pressure based on the soil column pressure, γh (h: the height of backfill above the CCT), needs to be properly modified. Considering different influential factors, four corresponding coefficients are proposed: : cross-sectional shape of CCT effect, : stiffness of backfill effect, : width of CCT effect, and : coupling effect of slope angle, θ, and the ratio of B/D. It is found that has little influence; the and reduce and amplifies the γh. The corresponding general forms for these coefficients are determined based on finite element analysis results. A general equation for estimating vertical earth pressure for the HFCCT including these four coefficients is proposed. Meanwhile, this general form is verified by the numerical analysis results and experimental results for different cases. Therefore, this proposed equation is applicable to estimate the vertical earth pressure for existing or newly designed HFCCT. Furthermore, this proposed method can significantly reduce the computational work in engineering analysis.

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Sheng Li

Papers

Load reduction on high-filled cut-and-cover tunnel using discrete element method

Alternative Hydronic Pavement Heating System using Deep Direct Use of Geothermal Hot Water

Coupled Effect of Expanded Polystyrene and Geogrid on Load Reduction for High-Filled Cut-and-Cover Tunnels Using the Discrete-Element Method

Coupled Effect of Cross-Sectional Shape and Load Reduction on High-Filled Cut-and-Cover Tunnels Considering Soil–Structure Interaction

Modification of Vertical Earth Pressure Formulas for High Fill Cut-and-Cover Tunnels Using Experimental and Numerical Methods