J. Earth Syst. Sci. (2020) 129:144 Ó Indian Academy of Sciences https://doi.org/10.1007/s12040-020-01403-2 (0123456789().,-volV)(0123456789().,-volV) Seismic liquefaction potential assessment of Andhra Pradesh Capital region USHA SAI BANDARU and VENKATA RAMA SUBBA RAO GODAVARTHI* Department of Civil Engineering, Velagapudi Ramakrishna Siddhartha Engineering College, Vijayawada, Andhra Pradesh, India. *Corresponding author. e-mail: [email protected] MS received 24 April 2018; revised 22 February 2020; accepted 16 March 2020 Seismic liquefaction hazard is an actuated ground failure which is responsible for significant damage to life and property. Andhra Pradesh state authorities are aiming to develop major infrastructural projects in the capital region. Liquefaction Potential Index (LPI) can predict the severity of liquefaction at a place. The present work aims at assessing liquefaction severity using LPI for different locations in the new capital region of Indian state, Andhra Pradesh. Further, current study presents a preliminary liquefaction severity map of the Andhra Pradesh state Capital region. This study reveals that the majority of the locations in this region may not be proned to liquefaction in the event of light earthquakes. Keywords. Liquefaction potential; SPT; magnitude of earthquake; LPI. 1. Introduction of ground, severity and frequency of the ground motion, kind of soil and thickness of soil deposit, In numerous major earthquakes, liquefaction and distribution of grain size, Bnes content, plasticity of related ground failures were widely observed. Liq- Bnes, degree of saturation, relative density, con- uefaction happens in saturated soils, that is, soil Bning pressure, permeability properties of soil where the space between various particles is fully layer, position and ground water table, etc. (Chung saturated with water. Liquefaction is a phe- and Rogers 2017). Liquefaction-actuated ground nomenon in which earthquake loading or other failure aAects the thickness of liqueBed and non- rapid loading which reduces the soil’s strength and liqueBed soil layers (Dixit et al. 2012). Measures to stiAness. The pressure exerted by the water on the mitigate the harms caused by liquefaction require thicknesses of the soil which aAects how tightly the exact assessment of liquefaction capability of soils. layers are packed together themselves. The water In general, factor of safety against liquefaction pressure is relatively significant in an earthquake (FSL) is used for evaluation of liquefaction sus- and water pressure increases during earthquake. As ceptibility. FSL is the fraction of cyclic resistance liquefaction happens, the soil strength reduces for ratio (CRR) to cyclic shear stress ratio. If the value the infrastructure to support foundation and of FSL is B1, the soil is susceptible to liquefaction bridges. Tilt or slide occurs when the liqueBed soil (L). If the value of FSL [1, the soil is not suscep- exerts high pressure. Increasing water pressure tible to liquefaction (NL). FSL has a limitation that may also cause landslides and lead dams to fall. it will not speak about the severity of liquefaction Soil liquefaction relies on the earthquake magni- potential. Liquefaction potential index (LPI) tude (Mw), conditions speciBc to site, acceleration was suggested by Iwasaki et al. (1978, 1982)to 144 Page 2 of 9 J. Earth Syst. Sci. (2020) 129:144 overcome the limitations of FSL. LPI estimates the of Krishna delta. Krishna River is the Capital severity of liquefaction to cause harm at surface region’s biggest perennial river which crosses the level of the site. region about a length of 135 km. 1.1 Study area – Andhra Pradesh Capital region 1.2 Geology and lithology The capital region with India map was presented in The soils in the capital region were primarily red Bgure 1. Andhra Pradesh Capital region covered gravel, alluvial, black cotton, loams of sand clay with plateau, mountains and Cat terrains. Coastline and loams of red. Iron oxide and limestone are the is 21 km away from the border of the capital region. major minerals found in this region. Minor miner- Kondapalli hill area extends in the Krishna district als are granite, rough rock, gravel, quartz bricks, between Vijayawada and Nandigama for a length of sand and highway metal. South of Vijayawada, the about 24 km. Other lesser hills are Mogalarajpuram, Krishna River constructed up its delta. So, with Jammalavoidurgam, and Indrakiladri (Vijayawada). great lithological structures, Tulluru had a good The southern belt is made up of rich soils in the region basement. North, northeast and south of Nuzvid Figure 1. Map showing the Andhra Pradesh Capital region. J. Earth Syst. Sci. (2020) 129:144 Page 3 of 9 144 are revealed Kamthi sandstone. Amaravathi was Deepankar (2017) have done seismic liquefaction the capital city of Andhra Pradesh and it lies in hazard analysis and mapping of existing important Guntur district. Amaravathi city was underlined buildings in Mumbai city. A comprehensive lique- by multiple geological structures from Archean to faction susceptibility assessment of Kolkata city Recent (Rambabu et al. 2015). was done by Nath et al. (2017). Liquefaction potential map for Kanpur city and Allahabad city were performed by Naik and Patra (2018). 1.3 Historical earthquakes Anbazhagan et al. (2019) studied the seismic site The historical earthquakes in this region are classiBcation of Himalayan region. Studies in rela- collected from Andhra Pradesh State Disaster tion to seismic microzonation of Chandigarh were Management Authority (APSDMA) and the same done by Kandpal et al. (2019). Liquefaction sus- was presented in table 1. According to seismic zone ceptibility of central Kerala has been studied by mapping code (IS: 1893-Part 1, 2016), capital Akhila et al. (2019). region will experience maximum earthquake of 6.5 magnitudes on the Richter scale. For instance, the 2. Methodology worst case scenario in the capital region may experience an earthquake of a magnitude up to 7.5. A simpliBed approach for liquefaction vulnerability assessment using standard penetration test (SPT) 1.4 Liquefaction studies in India value was explained by various investigators (Seed and Idriss 1971; Poulos et al. 1985; Seed et al. 1985; Seismic microzonation of Delhi region was done by Idriss and Boulanger 2006). SimpliBed approach Rao and Neelima (2007). Seismic microzonation for liquefaction vulnerability assessment starts of Bangalore city was performed by Anbazhagan with computation of CSR. For computing CSR, and Sitharam (2008). Assessment of liquefaction PGA is required. SPT value is utilized while eval- potential of Guwahati city was done by Binu and uating the CRR of in-situ soil. SPT was conducted Hazarika (2013). Liquefaction hazard mapping of according to the standard operating procedure laid Lucknow was examined by Abhishek et al. (2013). in IS: 2131 (1981). The SPT (instrument setup was Anbazhagan et al. (2014) presented seismic hazard shown in Bgure 2) is done in the boreholes of 150 map of Coimbatore city. Anbazhagan et al. (2015) mm diameter. In this test, a standard ‘split-spoon’ presented a seismic intensity map of South India sampler is driven through soil by applying repeti- for estimated potential earthquakes. Reshma and tive blows with a 63.5 kg weight of hammer falling Table 1. Historical earthquakes in and around the capital region from APSDMA (2017)(http://apsdma.ap.gov.in/view- earthquakes). Sl. no. Place Date Magnitude Sl. no. Place Date Magnitude 1 Ongole–Kanuparti 18.10.1800 4.3 19 Ongole 25.10.1976 3.5 2 Guntur 21.07.1859 4.3 20 Darsi–Ongole 25.05.1977 3.5 3 Guntur 02.08.1859 3.7 21 Chirala 2.11.1981 3.5 4 Guntur 09.08.1859 3.7 22 Ongole 18.08.1986 3.5 5 Ongole 12.10.1859 5.0 23 Ongole 19.08.1986 3.5 6 Krishna 24.07.1861 3.7 24 Ongole 03.12.1987 4.0 7 Krishna 13.01.1862 3.7 25 Ongole 03.12.1987 4.0 8 Vinukonda 6.01.1867 3.7 26 Ongole 14.11.1992 3.6 9 Ongole 11.03.1867 3.7 27 Guntur 24.05.1995 4.0 10 Ongole 13.10.1956 5.0 28 Ongole 21.10.1995 3.9 11 Ongole 12.10.1959 5.0 29 Addanki 04.08.1996 4.1 12 Ongole–Guntur 08.10.1960 4.3 30 Guntur 14.04.1997 3.8 13 Guntur 05.12.1963 3.7 31 Ongole 04.08.2006 3.4 14 Ongole 27.03.1967 5.4 32 South coast of AP 16.12.2006 3.5 15 Vinukonda 11.08.1967 3.5 33 Sattenapalli 29.10.2012 3.9 16 Vinukonda 06.01.1967 3.7 34 Ongole 06.06.2013 2.9 17 Ongole 28.07.1971 4.3 35 Guntur 22.05.2014 – 18 Ongole 28.11.1974 3.9 144 Page 4 of 9 J. Earth Syst. Sci. (2020) 129:144 Finally, factor of safety against liquefaction (FSL) was found by dividing CRR with CSR. CSR was ascertained from the below expression (Idriss and Boulanger 2006). ! ! a r CSR ¼ 0:65 max v0  r ; ð1Þ g r0 d v0 where amax is the peak ground acceleration, g is amax the acceleration due to gravity, g is the factor of zone, rv0 is the total overburden pressure (in kPa), r0 is the eAective vertical overburden v0 2 pressure (in kN/m ), rd is the coefBcient of stress reduction. ½aðÞþz ðÞbðÞÂz M rd ¼ e ; ð2Þ Figure 2. SPT instrument. where M is the earthquake magnitude, hi from an elevation of 750 mm. The resistance of z aðÞ¼Àz 1:012 À 1:126 sin þ 5:133 ; ð3Þ penetration (N) is the number of blows needs to 11:73 penetrate the split-spoon through soil for the pen- hi z etration of 300 mm. The SPT values observed in bðÞ¼z 0:106 þ 0:118 sin þ 5:142 ; ð4Þ the Beld was corrected and the detailed procedure 11:28 for applying various corrections to arrive corrected In equations (3 and 4), z is the depth of soil N value, i.e., (N1)60 was given in Bgure 3.