Real-Time Monitoring of Climactic and Geotechnical Variables during Landslides on the Slopes of Serra do Mar and Serra da Mantiqueira (São Paulo State, Brazil)

Abstract

The municipalities of Ubatuba, Campos do Jordão, and São José dos Campos are located in the region of São Paulo State (Brazil). These municipalities are recognized nationally for having an elevated number of recorded landslides on slopes and embankments. In addition, these municipalities contain multiple areas that are at risk for landslides. Various soil landslides occurred in these municipalities in January 2013, when real-time climactic and geotechnical variables were monitored by automatic rain gauges, humidity sensors and soil temperature and suction devices. The resulting data were used to understand the functions of each variable in the occurrence of landslides. Analyses of rainfall, humidity and soil temperature were used with field investigations to formulate a hypothesis regarding the predominant rupture mechanism and the role of each monitored variable in the deflagration of the soil landslides that occurred in the three studied municipalities. The geotechnical variable data revealed that both temperature and soil moisture contents played fundamental roles in the deflagration of shallow planar landslides in urban areas. The hourly rain intensity and/or rainfall accumulation for 24 and/or 72 h were responsible for the deflagration of the landslides that occurred in the studied areas, along with the existing anthropic constraints in the risk areas. Significant variations did not occur in the soil suction data during the landslides, principally due to the unsatisfactory sensor precision when reading field suction between −10 and −100 kPA (±25%).

The use of surface wave methods in terrain suceptible to shallow land slides in the city of Campos do Jordão, Brazil

“…As a result, the steep terrain is improperly occupied, where cuts and landfills are often carried out by the residents themselves, often resulting in precarious and dangerous slope stability issues (Ahrendt, 2005). (Ahrendt, 2005) and recently (bottom right) (Mendes et al, 2015) show the rapid development of the region. Note that north is pointing up in all images.…”

“…The site was chosen because it sits on a relatively stable slope for the safety of personnel, and because it shares many geological characteristics with nearby areas where landslides have previously occurred. Due to these characteristics, a geotechnical investigation was conducted at the site by Mendes et al (2015). The site is located less than 200 meters from an area known to have suffered from landslides during the region's infamous landslide event of the 1999-2000 winter.…”

“…Santo Antônio and nearby neighborhoods were devastated after widespread landslides destroyed many homes between December 1999 and January 2000 after heavy rainstorms hit the region. The disaster became the focus of many research efforts afterwards (Ahrendt, 2005;Mendes 2012;Mendes et al, 2015). These research efforts have resulted in some valuable information, however a detailed near surface velocity profile has yet to be available.…”

“…A near-surface geotechnical investigation was performed by Mendes et al (2015) within meters of the geophone array line used in this research. Mendes also divides the nearsurface into three layers; the topsoil (H1), mature residual soil that is relatively homogenous with no rock matrix structure (H2), and young residual soil or saprolites with a rock matrix structure composed of bedrock pieces that have not fully weathered into saprolite.…”

“…Geotechnical characterization in the form of sieve analysis, soil gran density, natural density, and Atterberg limits (liquid and plastic) were performed from three deformed samples that were collected on site (see Figure 3.12, Mendes et al, 2015). The results are shown in Table 3.1.…”