Geotechnical Characteristics of Mass Movements in Manaus – AM

For decades, the urban area of ​​Manaus has been expanding inappropriately, and horizontally, clearing forests and occupying unfit areas for housing. Administrative zones, like the East Zone, did not have the same evolution in their urban infrastructure as this expansion happened. Thus, mass movements arise, mainly due to anthropic factors associated with the presence of geological, topographic and environmental conditions. For the Municipality of Manaus, there is the landslide risk analysis addressed in 2012 by the Geological Survey of Brazil (CPRM) in conjunction with the Municipal Civil Defense. Currently, this risk diagnosis is made through field visits, surface investigation and completion of descriptive form in order to store information of the area under study. This methodology, described by the Ministry of Cities, is widely applied in several Brazilian municipalities with satisfactory results. In this context, the aforementioned procedure was used in the present work, and aiming to reduce subjectivity, the Hierarchical Analysis Process (AHP) was added. In the present study it was observed that this system, besides not modifying the basic approach of the Ministry of Cities method, incorporated a quantitative examination that verified the contribution (in the form of weights) of each danger indicator, besides hierarchizing the slopes with problem. Thus, it was found that the AHP method compared to that applied by the Ministry of the City were similar in the evaluation of the slopes of Jorge Teixeira neighborhood, located in the east zone of Manaus, the region object of the present study, chosen because it was more susceptible to landslide events (CPRM, 2012), aggravated by anthropogenic conditions. It is also verified that the slope stability, employing Bishop's method with the aid of Slope / W software for the slope (S01) in Jorge Teixeira neighborhood, registered results compatible with that found by the AHP method.

Study on the Effects of the Rainwater Seepage on Slope Stability

The work condition of the highway, which is usually built in mountainous regions, is complex relative to the ordinary road. Slope instability accident caused by the seepage of rainwater usually occurred in the rainy season. The mechanism for seepage failure of slope was investigated by used the Mohr-Coulomb criterion and the principle of effective stress. The effect of rain intensity on slope stability was equivalently instead by the effect of moisture content on slope stability. The influence of moisture content on the safety factor of slope stability was further calculated according to the Bishop’s method. The degeneration of safety factor follow to the moisture content was presented in the percentage.

Equivalent Proof and Applicability Evaluation of Two Types of Simplified Bishop’s Methods

In order to consider the influence of water pressure on cohesive soil slope with groundwater, the local and global water pressure methods are proposed. The equivalence and applicability of the two methods based on the simplified Bishop’s method are analyzed. The local water pressure method considers the water pressures on boundaries as components and the global water pressure method considers the water pressures as a resultant force. The physical analysis and numerical verification showed these two methods are completely equivalent. While the global water pressure method is more convenient in hydrostatic condition, the local water pressure method is prior in seepage condition. It is also pointed out that there are significant defects in some regular expressions of simplified Bishop’s method. Because they neglect the moment generated by water pressure on the top boundary of slope or wrongly evaluate of the hydrodynamic failure states with hydrostatic stress parameters.

Analysis on Qinyu Landslide and Treatment Measures in G212 Highway

G212 highway is a primary route from Gansu to Sichuan province. Landslides and debris flows along G212 highway often occurred in Longnan region of Gansu province. According to finite element method of saturated-unsaturated seepage, variation of pore water pressure of saturated-unsaturated slope under transient seepage field was simulated in the cases of rainfall and groundwater and safe factor of the slope stability was obtained, based on Fredlund’s strength theory of unsaturated soil and Bishop’s method. As an example of the Qinyu west landslide, the drainage, guarding face wall and frame structure with pre-stress anchor rod were very effective and feasible for the landslide treatment measures.

Application de la méthode de Bishop simplifiée aux remblais renforcés par les géosynthétiques

A new approach to stability analysis and design of geosynthetic reinforced slopes based on Bishop's method is presented. The effect of sheet inclination across the slip surface on the safety factor or on tensile strength of the sheet is materialized by the introduction, in the computation, of a factor varying from 0 to 1. The reason for this move is to take the flexibility of the sheet into account. Two tables of procedure were made up in case of analysis and design. Some examples are presented by way of illustrations. Key words : slope, safety, slip surface, slice, geosynthetics.

Influence de surcharges concentrées sur la stabilité des talus

Concentrated loads, in particular when horizontal, are not properly taken into account in the simple methods of slope stability analysis such as Bishop's method. It is therefore proposed to replace in Bishop's equations any surcharge by a statically equivalent stress distribution on the failure surface. For reasons of simplicity, this distribution is taken according to Flamant, slightly modified to fit stress distributions obtained from finite element studies. An application is presented in the form of the optimization of a slope stabilization by tie-backs. [Journal translation]