Natural heterogeneity of soil hydraulic properties is significant for the design and construction of geotechnical structures, and should be adequately characterized. Accurate measurements of hydraulic properties remain a difficult job and do not always work well for further design and analysis. Field hydraulic monitoring data reflects the overall slope performance and provide a more representative estimation of in-situ soil hydraulic properties for back analysis. The objective of this study is to explore the conditions under which monitoring data can provide reliable estimates of hydraulic parameters. Different distributions of soil heterogeneity generate a total number of 500 sets of synesthetic monitoring data. Bayesian inversion with the integration of Karhunen-Loève (K-L) and polynomial chaos expansion (PCE) is chosen to estimate the spatially varied saturated coefficient of permeability k_s. The results show that the method is accurate and reliable, with less than 3% percentage error and 0.08 coefficient of variation (COV) around the monitoring points. There are two characteristics of the best-estimated fields. First, the ranges of k_s for best-estimated fields are much narrower than the worst estimated fields. Second, when the larger k_s values are distributed in the unsaturated zone of slope crest, it will lead to the best estimation. It is suggested that monitoring data can provide a reliable estimation of heterogeneous k_s when the ratio of ground surface flux to k_s in the unsaturated zone of slope crest is less than 1/150. Small values of k_s in the slope crest result in the response of pressure head far from the responses of homogenous k_s in the unsaturated zone. This complex response of the pressure head further causes the ill identification of k_s by Bayesian estimation.

Cement-stabilization of weak and soft soils is an efficient way for ground improvement. Traditional Portland cement remains the most popular cementitious material in practice, and thus, a proper dosage design of cement-stabilized soil is of practical interest to meet the sustainable engineering requirements and to remedy environmental concerns. Based on the unconfined compression test of cement-stabilized Qiantang River silty clay, the effects of cement content, mixing moisture content, mixing-water-to-cement ratio, and curing time on the unconfined compressive strength were investigated. The results show that the mixing-water-to-cement ratio can comprehensively characterize the effects of cement content and water content on the unconfined compressive strength of the cement-stabilized clay. A prediction method for the unconfined compressive strength of cement-stabilized Qiantang River silty clay has been proposed with considerations for mixing-water-to-cement ratio and curing time. By comparing the experimental data of the present study with the existing literature data, it is found that there is a unified relationship between the unconfined compressive strength and the mixing-water-to-cement ratio of cement-stabilized Qiantang River silty clay, kaolin, Singapore marine clay, and Bangkok clay under the same curing time. The prediction method recommended by the standard may overestimate the unconfined compressive strength of cement-stabilized Qiantang River silty clay cured for 90 days.