A complete picture of the deformation characteristics (distribution and evolution) of the geotechnical infrastructures serves as superior information for understanding their potential instability mechanism. How to monitor more completely and accurately the deformation of these infrastructures (either artificial or natural) in the field expediently and roundly remains a scientific topic. The conventional deformation monitoring methods are mostly carried out at a limited number of discrete points and cannot acquire the deformation data of the whole structure. In this paper, a new monitoring methodology of dam deformation and associated results interpretation is presented by taking the advantages of the terrestrial laser scanning (TLS), which, in contrast with most of the conventional methods, is capable of capturing the geometric information at a huge amount of points over an object in a relatively fast manner. By employing the non-uniform rational B-splines (NURBS) technology, the high spatial resolution models of the monitored geotechnical objects can be created with sufficient accuracy based on these point cloud data obtained from application of the TLS. Finally, the characteristics of deformation, to which the geotechnical infrastructures have been subjected, are interpreted more completely according to the models created based on a series of consecutive monitoring exercises at different times. The present methodology is applied to the Changheba earth-rock dam, which allows the visualization of deformation over the entire dam during different periods. Results from analysis of the surface deformation distribution show that the surface deformations in the middle are generally larger than those on both sides near the bank, and the deformations increase with the increase of the elevations. The results from the present application highlight that the adhibition of the TLS and NURBS technology permits a better understanding of deformation behavior of geotechnical objects of large size in the field.

Debris avalanches generally have massive mobility and extensive deposited area, which have strong relation to the granular effect. The granular effect is an outcome from the interaction (based on frictional mechanism) among particles. Discrepancy of grain composition, for instance the difference of particle size and their proportion of particles, is a key factor to influence granular effect. A series of laboratory tests have been conducted to research the granular effects on depositional processes of debris avalanches containing fine- and coarse-grained particles. The velocity of debris front, the morphology characteristics and runout distance of the debris avalanche are considered in detail, and the mass parameter and the size parameter are introduced in analysis for the research of granular effect. The experimental results indicate that the granular effects can decrease the dissipation of momentum and increase the accumulation region, leading to further runout distance and more extensive deposited areas. Further, the velocity, the range of depositions of debris avalanches are larger than that in other conditions when the proportion of fine-grained particles is 30%, especially the materials consist of heterogeneous granular. It means there have a critical mass parameter in experiments which lead to the high efficiency of granular effects, and the granular effect is weakening in homogeneous granular composition.

To get a better understanding of failure mechanism of slopes in soils that exhibit expansive characteristics subjected to any type of inundations, particularly, when the soils switch from unsaturated to saturated states, the field study may severe as a rather effective method for providing the most representative information. However, field investigation is usually time-consuming and expensive. While, numerical simulation provides a faster way for producing quantitative interpretation of several complicated mechanisms. In this paper, a field experiment is studied numerically, which involves simulation of water flow within the slope profile by finite element method, followed by quantification of the stability of potential failure mass by the classic slices Method. Special emphasis is placed on the effects of cracks on the flow behavior in the shallow layer, which is one of the most essential characteristics in expansive soils. The Bimodal Soil Water Characteristic curve, together with the Bimodal permeability functions, is found to be more effective in reproducing the change of flow regime (pore water pressure and water content) from the finite element water flow analyses, in comparison to the Unimodal functional properties. The stability analyses illustrate that the shear behavior of soils within the shallow layer should be better described by strength parameters measured under lower confining pressure close to the field conditions. This implies the actual mobilized shear strength of expansive soils in shallow layer should be better modeled with a non-linear strength model that is able to accommodate the low stress conditions.

The construction of large earth/rock fill dams, albeit its remarkable progress, still relies largely on past experiences. Therefore, a comprehensive yet dependable monitoring program is particularly beneficial for guiding the practice. However, conventional measurements can only produce limited discrete data. This paper exploits the potential of the terrestrial laser scanning (TLS) for an accurate inventory of as-built states of a concrete-faced rockfill dam under construction and for a full-field analysis of the 3D deformation pattern over its upstream face. For the former, a well-designed 3D geodetic system, with a particular consideration of the topography, promises a regulated acquisition of high-quality and blind-zone-free point cloud at field and also eases the cumbersome data registration process while maintaining its precision in house. For the latter, a problem-tailored processing pipeline is proposed for deformation extraction. Its core idea is to achieve a highly precise alignment of the point clouds with Iterative Closed Point algorithms from different epochs in datum areas that displays a featured, undeformed geometry at stable positions across epochs. Then, the alignment transformation matrix is applied to the point clouds of respective upstream face for each epoch, followed by pairwise comparisons of multiple adjusted point clouds for deformation evaluation. A processing pipeline is used to exploit the peal scene data redundancy of the GLQ dam acquired at six different epochs. Statistical analysis shows that satisfactory accuracy for deformation detection can be repeatably achieved, regardless of the scanner’s positioning uncertainties. The obtained 3D deformation patterns are characterised by three different zones: practically undeformed, outward and inward deformed zones. Their evolutions comply well with real construction stages and unique 3D valley topography. Abundant deformation results highlight the potential of TLS combined with the proposed data processing pipeline for cost-efficient monitoring of huge infrastructures compared to conventional labor-intense measurements.

With recent advances in calculation methods, the external factors that affect slope stability, such as water content fluctuations and self-configuration, can be more easily assessed. In this study, a three-dimensional finite element strength reduction method was used to analyze the stability of three-dimensional slopes under fluctuating water conditions. Based on soil parameter variations in engineering practice, the calculation models were established using heterogeneous layers, including a cover layer with inferior properties. An analysis of seepage, deformation and slope stability was carried out with 27 different models, including three different slope gradients and nine different corner angles under five different hydraulic conditions. The failure mechanism has been shown to be closely related to the change in matric suction of unsaturated soils and the geometric slope configuration. Finally, the effect of geometry (surface shape, turning corner and slope gradient) and water (fluctuations) on slope stability are discussed in detail. Emphasis is given to comparing safety factors obtained considering or ignoring matric suction.