Local Site Effects and Ground Failures

Local site effects play an important role in causing damage to structures during earthquakes. Thus, one of the aim of seismologists and geotechnical engineers is to characterize the soil for the region prior to seismic hazard assessment. In the present work, an endeavor is made to study the depth of bedrock in Indo-Gangetic Plains from Seismotectonic Atlas of India [6]. A huge variation of bedrock depth ranging from 0 to 4000 m indicates the presence of thick soil cover in the study region. Roorkee city, situated in the foothills of Himalayas has a bedrock depth of around 3000 m and due to the presence of this huge soil cover, the occurrence of any great seismic event will pose a threat to both life and property as properties of propagating waves change as they travel toward the surface. The site characterization is carried out by MASW and Microtremor methods and shear wave velocity profiles are estimated with the thickness of soil. The region has lower values of shear wave velocity and falls in Site Class D. Ground Response Analysis (GRA) of the site is performed using STRATA [9] to Uttarkashi Earthquake (1991) and Chamoli Earthquake (1999) and is compared with the suggested response spectrum in (IS, in (Part 1): 2002 Indian Standard, Criteria for earthquake resistance design of structures, Fifth Revision, Part-I, Bureau of Indian Standard, New Delhi, 1893):2002 (Part 1). The comparison of the response spectrum from two earthquakes inhibits higher variation as provided in the IS Code.

The main objectives of the present paper are: (i) to identify the areas in Kalyani region, Kolkata, i.e. AIIMS Kolkata campus in which soil formations are prone to amplifying ground motions and (ii) to analytically evaluate amplification ratio using computer program for earthquake site response analysis. Peak ground acceleration at different depth is calculated for all the selected six sites with the help of soil profile. For this purpose, one-dimensional linear ground response analysis is done by the help of DEEPSOIL V-7.0 computer program. It can be observed that from the results peak ground acceleration of different site is varying from 0.159 to 0.190 g and the soil amplification value is ranging from 0.996 to 1.190 for peak ground acceleration of 0.16 g.

Subsurface shear wave velocity plays an important role in designing earthquake-resistant structures. Average shear wave velocity up to 30 m depth, known as Vs30, is used as a common design parameter. Ambient noise data that is generated by ground vibrations due to the passing of vehicles or other passive sources carry an important information about the subsurface shear wave velocity structure of the region. The seismic instrument records these disturbances along with three different directions i.e. two horizontal and one vertical. The ratio of the spectral amplitude of the horizontal to the vertical component is an important factor that is dependent on subsurface velocity structure of the investigating area. Ground vibration data from ambient noise recording system has been recorded at Bayasi site in the Garhwal Himalaya. A computer code DISHV in FORTRAN has been developed in this work for obtaining HV curve having a limited data from a large sampled HV curve having similar spectral property. The obtained output from DISH has been effectively used as an input to the HV-Inv software developed by Garcia et al. (Comput Geosci 97:67–78, 2016). The HV curve obtained from recorded data is modelled with a simulated annealing algorithm. The obtained velocity model from Simulated Annealing algorithm is further refined using forward modelling approach to match obtained and theoretical HV curve.

The dynamic stiffness and damping of the soil material, depth of the soil profile, impedance between the soil and the underlying bedrock and soil nonlinearity are the factors influencing the local site response. The important parameter in assessing the site response is the “amplification factor,” which is usually correlated to Shear Wave velocity in the top 30 m (Vs(30)). Though using VS(30) as an index for amplification is simple and robust, it is not recommended for site-specific applications. In the present study, two distinct soil types i.e. “Sand” and “Clay” with the same value of VS(30) demonstrated variable amplification characteristics. Hence, distinct site amplification models were derived for the two soil types considering the intensity of the input bedrock motion as the primary independent variable. The borehole data from nearly 50 locations in North Kerala, an intraplate region in the Southern part of India was collected. The ground response was simulated in 1-dimension considering equivalent linear behavior of soils on the SHAKE 2000 platform. The ground motions used in the simulation were scaled to the target spectrum obtained from the regional seismic hazard assessment. The average spectral amplification observed is 5 for “Clay” and 3.5 for “Sand” in the study region. The soil profiles categorized as “sand” exhibits nonlinear behavior. “Clay” deposits reveal sustained amplification at longer periods and hence, can significantly influence ground response during longer duration ground shaking. The empirical amplification equations developed from the study can be used to modify the generic ground motion prediction models to region-specific applications.

Indo-Gangetic Basin (IGB) is the major geographical region of India extending from Punjab to Bihar including Uttar Pradesh (UP) and Haryana. In this region, major earthquake damages have been reported in the past. Several attempts have been made for different site response studies and estimation of earthquake risk in the region. However, most of them consider only shallow soil information < 50 m and available ground motions. Present study attempts to analyze the spatial variation of peak ground acceleration (PGA) at surface for possible future scenario earthquakes in and around IGB. The earthquakes were identified based on past seismic gaps and studies whose magnitudes ranged from Mw 7.5 to Mw 9.0. The earthquakes were simulated for 270 sites with available shear wave velocity data throughout the IGB. Using proper input parameters of soil column profiles, shear wave velocity, depth of input motion, suitable shear modulus reduction and damping curves; the detailed analyses were carried out using DEEPSOIL. This paper arrives at spatial variation of PGA at surface due to individual earthquakes. The response (bedrock as well as surface PGA) of different states toward each earthquake has been tabulated. Sites in Bihar reflect average and maximum surface PGA 0.15 g and 0.68 g, Uttar Pradesh 0.10 g and 1.18 g, Punjab and Haryana 0.12 g and 0.62 g respectively. These values are indicative of the sensitiveness toward earthquake damages. Maps representing surface PGA for each scenario earthquake were plotted giving detailed information about the surface seismic hazard of the area associated with each earthquake.

Varanasi (latitude 25°28′ N and longitude 82°96′ E), the cultural capital of India, is presently clustered with a maze of ancient narrow lanes (Gullies) and old buildings. Being a sacred city, it is not well planned and structured, due to lack of adherence to earthquake-resistant building design philosophies and techniques. Consequently, even a smaller magnitude of an earthquake can cause a considerable loss. The city is also near to Faizabad ridge, which has been seismically sedentary for last 300 years. Due to unavailability of earthquake ground motion (G.M.) records in this region, it is necessary to simulate G.M. based on regional seismic data. In this regard, the stochastic approach has been adopted for the synthesis of G.M. at bedrock level. An EXSIM methodology has been used in this study for synthesis of strong G.M. for various identified faults (Allahabad Fault, Azamgarh Fault, Gorakhpur Fault, Deoria Fault, Lucknow Fault, Siwan Fault, Shajhanpur Fault and Great Boundary Fault) around the city. Various stress drops 70, 100, 125, 150, 175 and 200 bars have been taken for simulations to account for uncertainty in stress drop. Acceleration time histories due to various faults for Varanasi city has been simulated and plotted. The maximum PGA estimated was 0.078 g for Azamgarh Fault at 200 bar among all the faults around the city. Further Response Spectra has been plotted for stress drop (70–200 bar).

Rapid growth and expansion in metropolitan cities necessitate the construction of buildings very close to existing structures. Whenever there is an excavation made adjacent to structure, the soil below the footings gets disturbed due to the lateral escape/displacement of soil and subsidence of soil, and hence a decrease in the bearing capacity of the soil around it. It is therefore required to assess the impact of construction on the nearby existing structures. The main aim of the study is to identify the variation in the dynamic properties of an existing frame structure adjacent to deep excavation and to find the response of the structure under seismic excitation. The analysis of structure without adjacent excavation is carried out and is treated as reference for six other cases considered. For three cases, the distance of excavation from existing frame structure is kept constant (as 0.5 m) and the depth of excavation is varied (1.5, 3, and 4.5 m). In other three cases, the depth of excavation is kept constant as 3 m and the distance of excavation from the existing frame is varied as 1, 2, and 3 m. In all the cases the width of excavation is kept constant as 3 m. The finite element modeling and analyses are carried out using software. The parameters studied are displacement, stress distribution, frequency, mode shapes, and amplitudes.

Solid waste management and disposal become a challenge on global level. Due to this rapid growth of waste, we are losing low-lying areas and valuable lands. Therefore, it is a peak demand to utilize the waste-filled areas for future use. The objective of this study is to get the dynamic response of a landfill site by using already available data in past studies. The response study of landfill site helps to predict the deformation and amplification behavior of the MSW fill sites. So that required preventive measures and ground improvement techniques can be implemented according to the response of site. The study area used in this paper includes landfill sites of Delhi area, which are mostly designed for about 20 m but now they are overfilled with more than 50 m. The aim is to find the seismic response of the site under defined dynamic loading. The response of landfill site was numerically analyzed both in one and two dimensions with the help of Cyclic1D and Plaxis2D software, respectively. The analysis performed is based on finite element method under the earthquake of magnitude of 6.5 with duration of 39.9 s and PGA of 0.3 g.

One-dimensional nonlinear (NL) ground response analysis (GRA) is carried out for four locations viz. Dharapur and Azara area, VIP and Rani area, Jalukbari area and Assam Engineering College (AEC) area of Guwahati city. The analysis is done with the help of 23 boreholes using Indo-Burma earthquake, 1997 recorded at Nongpoh station and Indo-Burma earthquake, 1988 recorded at Nongstoin station with duration 52.94 s. These two input motions are further scaled up to 0.18 and 0.36 g and used for the GRA analysis. The response of the substrata obtained after the analysis has been presented in terms of peak spectral acceleration, maximum shear stress profile, strain distribution and peak ground acceleration (PGA) for all the locations irrespective of every motions. For most of the locations, soil layers with high SPT N value, generally stiffer soil, resulted in a lower value of surface PGA compared to soft soil layers. The PGA and overall energy content of the strong motion significantly affect the response of a multilayered soil profile, keeping all other parameters constant. Higher strain amplitudes have been observed at various sites and at various depths of the soil profiles which may undergo settlement or earthquake-induced liquefaction. The peak spectral acceleration obtained is much higher for 0.36 g scaled motion compared with the spectral acceleration of rocky or hard soil sites (IS: 1893–2002) for both the earthquakes which indicate sensitiveness of the locations to the induced motions.

Ground Response Analysis (GRA) is required to be carried out for predicting ground surface motions and to evaluate dynamic properties of soil during an earthquake excitation. In this study one-dimensional equivalent linear (EL) and nonlinear (NL) GRA was carried out for five boreholes located in Golaghat district of Assam, India. This region falls under highly seismic zone ‘V’. The soil borehole log obtained from standard penetration test (SPT) confirmed alluvial deposits with layers of both coarse and fine-grained soils. The input motions of 2011 Sikkim earthquake of Mw 6.9 recorded at Gangtok station and 1999 Uttarkashi earthquake of Mw 6.8 recorded at Bhatwari station are considered for the analysis. The results are plotted in terms of peak ground acceleration (PGA), maximum stress ratio and maximum strain with depth, and spectral acceleration over range of periods. On comparison of EL and NL methods, the strain profile follows a similar trend along the depth of borehole from both methods. However on comparison of both the methods, NL methods showed maximum shear strain value. It was depicted that the PGA values for a particular site of interest can be determined directly from the peak horizontal acceleration (PHA) even in the absence of dynamic soil properties of the site. Such PGA values can be directly used for earthquake-induced liquefaction analysis and also for building design purposes.

In the present study, new elastic design response spectra (EDRS) for the deep and shallow region of the Indian subcontinent has been proposed for rock and soil site. For determining the EDRS for bedrock, 50 each rock recorded ground motions have been used for Intra and Interplate region. For determining the EDRS for soil sites, 250 and 178 ground motion for deep and shallow sites has been used, respectively. For SI, only few ground motions are available, hence for developing EDRS for shallow sites, ground motions recorded at similar tectonics have been used in the present study. Further, EDRS is derived based on Eurocode, i.e. normalized elastic design response spectra which is based on one parameter, i.e. effective ground acceleration at rock.

The paper examines the effect of liquefaction potential of the site due to normal earthquake and sequential earthquakes occurred in Japan. Two earthquakes have been considered (a) 2016 Kumamoto sequential earthquakes with mainshock (Mw = 7.3) and a couple of foreshock in the previous days (Mw = 6.2 and Mw = 6.5); and (b) 2005 Fukuoka-ken Seiho-oki earthquake (Mw = 7.0), the earthquake has only mainshock. With the help of available literatures, damages associated with the liquefaction was examined with reference to effect of preshaking, liquefaction history and earthquake pattern. It is evident that, liquefaction effects of the 2005 earthquake are larger than those associated with Kumamoto sequential earthquakes. It is inferred that liquefaction resistance and reliquefaction potential of the site was highly influenced by the seismic preshaking, liquefaction history and earthquake pattern. This is the most probable explanation for the higher liquefaction resistance exhibited by the Kumamoto earthquake. Preshaking effect is highly associated with earlier earthquake history or significant foreshocks as in the 2016 Kumamoto earthquakes. The occurrence of sequential earthquakes induces reliquefaction phenomenon in the site. It is concluded that, liquefaction history and preshaking effect of the site contributed to the enhanced liquefaction resistance of the site.

Basal geogrid reinforced embankments supported on vertical piles are proven to be a feasible and effective solution for constructing embankments over thick soft clay deposits and bridge approaching embankments. These solutions minimize the lateral displacements, total and differential settlements of embankment crest and toe by transmitting embankment loads into the deeper stratum through pile foundations and arching action of geogrid. Basal geogrid reinforcements provide good restraint against lateral spreading of the toe. Providing batter piles near the toe will further enhance this restraint against lateral spreading. Not many studies are available in literature on performance of batter piles below embankment toe, especially under seismic excitations. The present study aims to find the advantages of providing batter piles below embankment toe under seismic excitations. A 6 m high basal geogrid reinforced embankment having 1 V:1.5H side slope constructed over 28 m thick soft clay is considered for the 3-Dimensional finite element analysis. The soft clay is stabilized with 22 m long 300 mm diameter vertical and batter piles spaced at three times the pile diameter. Embankment crest vertical displacements, toe horizontal displacements, maximum differential settlements at the crest and crest lateral accelerations are analysed for different batter angles of 0°, 5°, 10°, 15°. Analysis of results reveals that larger the batter angle more is the reduction of toe horizontal displacements.

Low height embankments are widely used for construction of highways and rural roads in India. Sometimes, it becomes necessary to construct such types of embankment on soft foundation soil under unavoidable circumstances. In addition to the stability under static loading, seismic excitation very often plays a major role in the stability of such an embankment. So, to study the behaviour of such embankment under seismic loading becomes very important as the failures may lead to huge loss of property and life. The present study analyses the response of a low height embankment overlying soft foundation soil under seismic loading with the help of finite difference analysis using FLAC. The Mohr-Coulomb failure criterion is used to define the soil constitutive model for both embankment and foundation soil. A stiffer half-space has been considered below the soft foundation soil and the analysis has been performed varying the shear wave velocity of the stiffer half-space. Low to moderate level of shaking has been applied at the base of the stiffer half-space by scaling the original input motion of 1987 Loma Prieta earthquake.

In hilly regions of India, excavation of slope is a common practice for construction of roadways. Toe cutting of slopes is repeatedly carried out for construction of new roads or widening of existing roads with rapid growth in population needing urbanization. In earthquake prone hilly regions such as North Eastern part of India, seismic activity can play the role of a major triggering agent for catastrophic slope failure due to non-engineered and impromptu toe excavation. In majority of the cases, effect of toe cutting on hill slope stability under earthquake condition is studied based on Limit Equilibrium (LE) pseudo-static method, wherein the safety is measured in terms of a time independent single factor of safety (FoS) value. However, pseudo-static approach, in which earthquake is represented by a constant inertia force acting on the slope, cannot simulate the earthquake condition accurately and may overestimate the earthquake force. Hence, in this paper rigorous dynamic analysis is performed for safe and economical excavation of toe regions of the slope before road construction. The study reveals that the conventional pseudo-static analyses provide conservative results, which when used as a basis of mitigation measures, will lead to uneconomical stabilization technique.

On August 18, 2019, the Kinnaur region in the Indian state of Himachal Pradesh experienced many landslides due to heavy rains. In H.P.’s Kinnaur district, National Highway 5 was blocked, heavy rainfall triggered many landslides in isolated regions of Himachal Pradesh, blocking large number of roads, it was blocked near Ribba village of Kinnaur district causing heavy traffic jam. According to reports, this event resulted in the death of 22 people and a significant loss of property. This study presents the results of the Kinnaur landslide damage assessment derived from the analysis of very high-resolution images (VHR) received from different satellites. These datasets were obtained through a coordinated effort by the government organisation major disasters. The damage is mainly attributed to rock slides from the area of ​​the slope that later became debris flows by sanding the material along the exit zone.

Landslide is a natural disaster that occurs when rock, earth or debris flows to downward slope due to gravity after being detached from slope underneath. It is essential to know the geotechnical properties to analyse the causes of landslide. For the present study geotechnical investigation has been carried out on the slopes of Atharamura and Baramura Hill, Tripura. Results obtained from laboratory test and field investigation revealed that the underlying causes of the landslide could be (a) the geological formation of those hills (b) permeability through the different layers of soil (c) shear strength of the soil (d) cutting of hills slope for reconstruction and widening of the road. Landslide triggered due to heavy precipitation during the monsoon season.

Kerala has been witnessing a large number of slope failure issues nowadays. After 2018 and 2019 floods, due to the landslide activities occurred in Kerala hill regions, people are getting aware of the seriousness of the slope instability problems. Factors such as geomorphology, slope angle, terrain curvature, slope length and steepness, soil type and land use or land cover are considered to affecting slope stability. The present study concentrates on the stability of Kattipara and Meppady regions of hill soil slopes. 2018 Karincholamala landslide comes under Kattippara region, and 2019 Puthumala landslide occurred at Meppadi region. The study area faces several slope failure issues. Rainfall is the primary triggering factor of slope failures in the region. Human-made activities of deforestation, constructing high rise buildings at slopes and mining explorations take part in making slopes more vulnerable to failure. Disturbances of soil due to vehicle motions, quarrying, construction activities, and earthquakes can affect the dynamic stability of slopes. Before performing the stability analysis under static and dynamic loading conditions, strength properties of soils collected from those regions are determined after conducting the experiments. SLOPE/W software using Limit equilibrium and pseudo static methods are used to obtain the factor of safety of slopes. Results are indicating that the soil slopes are about to fail under static as well as pseudo static conditions if the soils along the slopes are submerged below the piezometric line.

Soil nailing is commonly used to stabilize cut slopes and earth retaining structures, embankments and sometimes to reduce the lateral earth pressure on retaining wall. This is an in-situ reinforcement technique that uses passive rigid bars usually made up of steel that can withstand tensile forces, shearing forces, and bending moments. In the present study, an attempt has been made to analyze the behavior of soil slope reinforced with soil nails by numerical simulation under seismic loading using a finite element numerical modeling tool, OptumG2. Two-dimensional models of the slope are considered (with and without nails) and subjected to static and dynamic loading to investigate the possible modes of failure (base failure, slope failure, and toe failure). The corresponding factor of safety values for unreinforced soil slope is calculated using the strength reduction method (SRM) at different slope angles ( $$\beta )$$ β ) at 30°, 40°, 50°. Based upon the obtained critical slope surface in the case of the unreinforced slope, soil nails are provisioned in the slope and the same is analyzed under gravity and seismic loading. A detailed investigation of reinforced soil slope has been conducted considering the key factors governing the factor of safety of reinforced slope namely length of the soil nails, the number of soil nails, spacing of soil nails (s), the inclination of soil nails ( $$\theta$$ θ ) in different slope angles ( $$\beta )$$ β ) under seismic loading with a peak horizontal ground acceleration = 0.12 g. The present study also investigates the possible failure patterns under static and seismic conditions, along with the analysis of the development of internal reactions in soil nails such as bending moment and shear force.

In this article, the factor of safety of a cohesive soil slope subjected to seismic load is determined by employing the variational method and pseudostatic analysis. Unlike the conventional limit equilibrium method, there is no requirement to consider any kinematical or static assumption in the variational method. The factor of safety (F) is defined as a functional which is minimized by using the Euler–Lagrangian equation. The (i) transversality and boundary conditions are imposed at the intersection of slip surface, and the slope surface, and (ii) continuity and natural boundary states are forced at the intermediate point of the slip surface. The soil is considered to be completely saturated and loaded under undrained conditions. The cohesion of the soil is assumed to increase linearly with depth. The critical slip surface and consequently critical factor of safety, Fs is being obtained by varying the slope geometry, soil properties, and seismic loadings. The available solutions compare quite well with the convenient solution for the pseudostatic slope stability analysis. The proposed design charts will be quite useful to practicing engineers.

This paper presents the seismic site characterization carried out for Karnataka (state level) as well as for India (country level) using topographic slope map derived from Digital Elevation Model (DEM) data. Two DEM data, SRTM, and ASTER were used to derive the slope maps. For Karnataka (state level), the slope map was generated from ASTER DEM considering a grid size of 5 × 5 km and for India (country level), the slope map was generated from SRTM DEM considering the grid size of 10 × 10 km. Based on the slope value, every grid point was characterized into various NEHRP site classes, and spatial variation of average shear wave velocity for top 30 m (Vs30) value throughout the study areas is presented in this paper. Peak horizontal acceleration (PHA) at bedrock level was evaluated for the same grid points using deterministic as well as probabilistic methodologies. The amplification factor for every grid point was obtained from the site coefficients corresponding to NEHRP site class. The surface level peak horizontal acceleration (PHA) was then evaluated for every grid point by multiplying bedrock level PHA with the corresponding amplification factor. Spatial variation of seismic hazard at the surface for the state of Karnataka as well as for entire India is presented in this paper.

In India, landslides are the most frequently occurring disaster in the regions of the Himalayas and the Western Ghats. They are mainly triggered either by rainfall or earthquake or the combination of both, causing severe damage to human life and infrastructure. This study presents a comprehensive use of the multi-criteria decision-making (MCDM) method in landslide risk assessment for the Tehri area in the state of Uttarakhand, India. The Tehri area is situated in the Lesser Himalaya of Garhwal hills which lies in zone IV of seismic zoning map of India. Because of the large-scale slope instability in the area, it has received the special attention of the researchers. In the recent past,—many landslide hazards and risk zonation is carried out for different regions in the Uttarakhand state. However, limited work is done considering temporal factors such as seismic ground shaking, rainfall, and seismic amplification at surface level. The DEM data is used to produce topographic characteristics such as slope, aspect, and relative relief. DEM data is also used for the detailed drainage analysis which includes topographic wetness index (TWI), stream power index (SPI), drainage buffer, and reservoir buffer. Seismic hazard analysis is performed using the deterministic methodology to estimate the peak horizontal acceleration. The amplification factor is calculated using the non-linear site amplification method. In this study, the analytical hierarchy process (AHP) is used to evaluate the landslide hazard index which is used to generate landslide hazard zonation (LHZ) map. Further, the landslide vulnerability assessment is done for the study area. The vulnerability map of the study area is derived in terms of landuse/landcover (LULC) using remote sensing data of Landsat 8 which can provide useful information that helps people to understand the risk of living in an area.

Landslide is a naturally occurring phenomenon in most of the mountainous regions of the world. Manipur, being a landlocked hilly state, is continuously facing the problems of landslides in the rainy seasons and the economic conditions are highly affected due to blockages of the highways of the region which served as the lifelines. So it becomes very important to check the problems caused due to this natural disaster. In this particular study, an attempt is being made for developing the landslide susceptibility mapping of the region using two GIS-based landslide susceptibility approaches––Analytic hierarchy approach and Frequency ratio approach. Eight causative factors Land Use Land Cover (LULC), Normalized Difference Vegetation Index (NDVI), slope, aspect, curvature, elevation, rainfall, and soil types are considered in the study. The output landslide susceptibility maps developed by the two different approaches have been compared and validation of both the models have been done using landslide locations of the region. Both the models show good accuracy but the Frequency Ratio shows higher accuracy when compared to the AHP approach.

The geotechnical engineers usually have difficulties in resolving complicated problems that involve a number of influencing parameters. Sometimes, it is also complicated to describe a problem mathematically. This study aims for an alternative algorithm known as Support Vector Machine (SVM), which can be used to solve the classification-type problem. In this study, liquefaction potential is analysed using influencing parameters viz. the Standard Penetration Test (SPT) values, different soil parameters, and depth of water table taken from a borehole database of a certain depth. This borehole database was prepared by collecting borehole data of different sites located in different parts of the country. A deterministic approach has been used to evaluate the liquefaction potential and it is expressed in the form of factor of safety (FS). The SVM model developed using the dataset of the liquefaction potential evaluated from a deterministic approach showed an overall accuracy of 96.8%.

Assessment of liquefaction potential of soils due to the earthquake has been carried out in this research using the nature-inspired Metaheuristic swarm-assisted algorithm (PSO). An assessment has been made on the basis of actual field data from the previous research. The field data consists of 59 sets having variables of total stress of soil (⌐o), effective stress of the soil (⌐′o), percentage fines, mean size of soil particles (D50), standard penetration value (SPT), the equivalent dynamic shear stress (Tav/⌐′o), maximum horizontal acceleration at ground surface (a/g) and the earthquake magnitude (M). PSO-based models were developed for both single variable and multivariable linear approaches. The results revealed that for the assessment of liquefaction of soils, the developed PSO models perform good estimations in terms of the errors and convergent solution. And also, with a damping coefficient and varying input variables, there is a significant improvement in the best solution. These developed models can be useful for practicing engineers in the field.

The liquefaction analyses proposed by various researchers such as Seed et al. (1971) and Seed and Idriss (1985) are based on Cyclic Stress Ratio (CSR) and Cyclic Resistance Ratio (CRR). The Cyclic Resistance Ratio (CRR) is dependent on corrected SPT blow count N60. Since hammer energy efficiency in India is different in comparison to the USA, it is necessary to develop an energy correction factor for India as the same was carried out by China and Japan. In this paper, the I.S. code procedure of liquefaction evaluation as well as energy correction factor developed for various countries were reviewed, and it is found that there is a need to develop one such energy correction factor for India.

In the present study, seismic soil liquefaction in terms of factor of safety against liquefaction (FS) is evaluated by the IS Code: (Criteria for earthquake resistant design of structures. Bureau of Indian Standards, New Delhi [5]) (Part-I, 2016) for a site of IIT Patna campus. The FS values against liquefaction are evaluated under three different earthquake magnitudes, namely, Mw = 6.0, 6.5 and 7.0. A design peak ground acceleration of 0.24 g used as the Patna city lies in the Zone IV of the seismic zoning map of India as per IS code. In this paper, an evaluation of the severity of liquefaction in the form of liquefaction potential index (LPI) is also determined. The LPI is determined at a single borehole location from the obtained factors of safety (FS) to predict the potential of liquefaction to cause damage at the site of interest. The evaluated FS and LPI values from IS Code are compared with Idriss and Boulanger (Soil Dyn Earthq Eng 26:115–130 [4]) procedures to investigate the liquefaction behavior for cohesionless soils. The FS and LPI results of both SPT-based semi-empirical procedures indicate that the soil liquefaction probability increases during earthquakes with magnitude ≥7.0 at this site. It is also observed that the values of FS from IS code match with Idriss and Boulanger (Soil Dyn Earthq Eng 26:115–130 [4]) results under high earthquake magnitude.

Earthquake-induced liquefaction is one of the most complex and interesting phenomenon in Geotechnical Earthquake Engineering. Liquefaction is a very significant phenomenon in alluvial soil deposits consisting of silty sand or sandy silt type of soils. Many different methods are available at present to assess the liquefaction potential of soil using in situ field test data. Generally, field tests like SPT are carried out and liquefaction assessment is done for each borehole. Different boreholes provide different depths up to which soil has potential for liquefaction for particular peak ground acceleration (PGA) and magnitude of Earthquake. Maximum liquefaction depth obtained from different boreholes is used to convey the liquefaction depth of the area in consideration. The greatest drawback of this approach is that results of only one borehole are used to conservatively predict the liquefaction potential of the entire area and results of remaining boreholes are neglected as they have predicted lesser depth of liquefaction. In case some more boreholes are drilled and assessment is done then there is quite a good probability that liquefaction depth of that area will change depending upon the SPT results from new boreholes. In this paper liquefaction potential assessment of alluvial soil site is carried out using SPT-based approach as proposed by NCEER [5]. SPT data of 25 boreholes are analyzed and converted into the equivalent single borehole using probabilistic approach to assess the liquefaction potential of alluvial soil site. Probabilistic approach is used to assess 95 percentile values of all variables required to assess Liquefaction potential like SPT blow counts, percentage fines, and soil density. As there is uncertainty present in the evaluation of these parameters at the site and in the laboratory, it is appropriate to evaluate these parameters based on a probabilistic approach using the best fit probabilistic distribution curve. Parameters required for assessing CSR (Cyclic Stress Ratio) like overburden pressure and effective overburden pressure are also analyzed using probabilistic distribution curves considering data from 25 boreholes and converting them into an equivalent single borehole. Factor of Safety (FOS) obtained using 50, 95, and 98 percentile values of different parameters is compared for converted equivalent single borehole.

On 28 September 2018, a 7.5 magnitude earthquake and subsequent tsunami hit Palu and Donggala in Central Sulawesi, Indonesia killing at least 2,245 people. Thousands of people were missing and over 10,000 were injured, of whom over 4,000 were with severe injuries. Nearly 75,000 were displaced in the three most affected areas: Donggala, Palu City, and Sigi. This paper discusses the performance of reinforced concrete buildings, bridges, port facilities, and lifelines in the Palu Earthquake. It was observed that a number of residential and commercial buildings were partially or fully collapsed and many sustained significant structural damages. The iconic twin steel arch cable-suspended Palu Bridge IV over the Palu River was collapsed. Lateral spreading induced by liquefaction resulted in huge housing damages and farm fields. It was seen from field investigations that possible reasons for building failure include the lack of confinement bars, improper confinement in beam and column joints, Ssrong beams weak columns and presence of soft story in multi-story buildings.

Reinforced retaining wall using geogrids is an effective method to deal with high and steep soil slope under complicated geological engineering conditions. There have been comparatively lesser studies on multi-tiered walls due to its limited application. This paper aims at making a comparative study of the behavior of three-tiered reinforced soil wall with small and large offset distances subjected to seismic excitations. A 2.8 m high numerical model of reinforced soil wall is developed using finite element software PLAXIS 2D. The numerical model is subjected to dynamic excitations of 0.4 g Kobe earthquake and results of the response of the numerical model are validated with shake table tests results of Ling et al. [7]. A 9 m high three-tiered wall with small offset distances (i.e., 0.5 m and 0.75 m) and large offset distances (1.5 m and 2.5 m) is simulated with validated model parameters. The tiered walls are subjected to seismic excitations of the Kobe earthquake at a peak acceleration of 0.4 g and the variation of lateral pressure, maximum reinforcement loads, and acceleration amplification factors of three-tiered walls with various offset distances are compared. The results showed that the lateral stress, maximum reinforcement load, and acceleration amplification factor decreases with the increasing tier offset.

To study the reduction in lateral earth pressure due to narrow reinforced earth (RE) wall, which is used for various earth retaining structures such as bridge abutments, retaining walls, and also where the available space for the reinforced earth (RE) walls is less than required. In a narrow RE wall, interface connection will be provided to prevent extensive pressure and cracks which are developed in-between existing wall and narrow RE wall. The main objective of this paper is to evaluate the earth pressure distribution for a narrow RE wall under static and cyclic loading considering the elastic (Flexible) and non-elastic (Rigid) behavior of the wall keeping the same relative density. Two major conditions, i.e., rigid boundary condition and flexible condition, which is used to perform a series of load–displacement and load-settlement test on the RE wall model using uniaxial geogrid reinforcement. The load–displacement-settlement is measured by using a conventional high capacity compressive mechanical jack and dial gauges. To validate the experimental results, the earth pressure distribution using Arching theory, Rankine theory, Coulomb theory. From results and analysis, there was a considerable variation is determined in load–displacement characteristics for both flexible and rigid boundary conditions. The percentage reduction in earth pressure was also observed in the case of a flexible RE wall as compared to a rigid narrow RE wall.

Liquefaction of soil significantly affects the life of buildings as well as the life of humans. Liquefaction develops when the shear strength of the soil is lesser to resist the shear stresses induced when subjected to dynamic loadings during vibration or an earthquake. In order to improve the load-bearing capacity so as to mitigate the liquefaction characteristics, the addition of chemicals in soil can also be used. Addition of chemicals can be done in two ways. The first method in which void spaces can be filled by grouting/stabilising material, whereas the second method is the mechanical stabilisation of external materials. The modifications of soil to upgrade its properties through grouting technologies are extensively popular these days. The present study is an attempt to study the non-conventional seismic liquefaction mitigation methods. Also, this study reviews the most significant laboratory tests with respect to liquefaction mitigation and compares colloidal silica with many other recent liquefaction mitigation techniques such as bentonite suspension grouting, bio-cementation, colloidal silica grout and sand–rubber tire shred mixtures. The current study revealed that the two main grouts, which can be used as a prospective liquefaction reduction materials in the upcoming era are colloidal silica and bentonite suspensions.