Landslide investigations in the northwest section

Authors: Zhaoguang Hu Wei Shan

Publish Date: 2015/10/03

Volume: 75, Issue: 2, Pages: 591-603

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Abstract

In the northwest section of the lesser Khingan range located in the highlatitude permafrost region of northeast China landslides are a frequent occurrence due to permafrost melting and atmospheric precipitation Highdensity resistivity HDR and groundpenetrating radar GPR methods are based on soil resistivity values and characteristics of radar wave reflection respectively The combination of these methods together with geological drilling can be used to determine the stratigraphic distribution of this region which will allow precise determination of the exact location of the sliding surface of the landslide Field test results show that the resistivity values and radar reflectivity characteristics of the soil in the landslide mass largely differ from those of the soil outside the mass The apparent resistivity values exhibit abrupt layering at the position of the sliding surface with a sudden decrease in apparent resistivity In addition the radar wave shows strong reflection at the position of the sliding surface where the amplitude of the radar wave exhibits a sudden increase Drilling results indicate that the soil has high water content at the location of the sliding surface of the landslide mass in the study area which is entirely consistent with the GPR and HDR results Thus in practice sudden changes in apparent resistivity values and abnormal radar wave reflection can be used as a basis for determining the location of sliding surfaces of landslide masses in this regionIn recent decades geophysical investigations for assessing stratigraphic distribution have become a common tool in geological research In situ geophysical techniques are able to measure physical parameters directly or indirectly linked with the lithological hydrological and geotechnical characteristics of the terrains related to the movement McCann and Forster 1990 Hack 2000 Benedetto et al 2013 These techniques less invasive than direct groundbased techniques ie drilling inclinometer laboratory tests provide information integrated on a greater volume of the soil thus overcoming the pointscale feature of classical geotechnical measurements Among the in situ geophysical techniques the highdensity resistivity HDR and groundpenetrating radar GPR methods have been increasingly applied for landslide investigation McCann and Forster 1990 Malehmir et al 2013 Timothy et al 2014HDR is based on the measure of electrical resistivity and can provide 2D and 3D images of its distribution in the subsoil It is one of the standard methods of geophysical prospecting for investigating shallow geological problems Cardarelli et al 2003 Yamakawa et al 2010 Donohue et al 2011 Sauvin et al 2014 Current applications of HDR focus on landslide recognition and permafrost detection while investigations on debris thickness in arctic and alpine environments are comparatively sparse Carpentier et al 2012 Donohue et al 2011 Perrone et al 2014 GPR is based on the measure of reflection of radar waves in the subsoil and is largely focused on the fields of natural resource exploration hydrogeology engineering and archaeological investigation Sass 2007 Sass et al 2008 Schrott and Sass 2008 Zajc et al 2014HDR and GPR are useful for determining characteristics such as the landslide main body geometry and surface of rupture and have been used in landslide investigations since the late 1970s Hack 2000 Havenith et al 2000 Bichler et al 2004 Drahor et al 2006 Rhim and Chul 2011 However the applicability of the various geophysical methods including regional limitations and reliability in estimating stratum thickness and sliding surface location of landslides in highlatitude permafrost regions in northeast China has not been addressed in detail Applications of geophysical prospecting on landslides in cold regions of the lesser Khingan range of China have been rareUsing landslide K178 + 530 as an example in this paper we present a combination of traditional methods drilling and mapping and geophysical techniques HDR and GPR applied to the landslide in the lesser Khingan range of northeast China in order to investigate the thickness and internal structure of the landslides that occur frequently as a result of melting permafrost and atmospheric precipitation in an effort to ascertain the applicability of HDR and GPR on this regional type of landslideThe geological structure of the study area belongs to the Khingan–Haixi fold belt From the bottom up the stratigraphy comprises Cretaceous mudstone Tertiary pebbly sandstone silty mudstone and powdery sandstone From the late Tertiary to the early Quaternary the lesser Khingan range experienced block uplift Due to longterm erosion and leveling loose sediments on the summit and slope of the hills have gradually thinned and the current residual layer is generally only 1–2 m thick The loose deposits accumulate mainly in the basin and valley areas between mountains with a thickness of about 10 m The soil is mainly composed of clayey silt mild clay and gravelly sand and the surface is covered with a relatively thick layer of grass peat and turf The surface vegetation is grassland and woodland and there are inverted trees in the woodlands

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