Probabilistic outlier detection for sparse multivariate geotechnical site investigation data using Bayesian learning

Various uncertainties arising during acquisition process of geoscience data may result in anomalous data instances(i.e.,outliers)that do not conform with the expected pattern of regular data instances.With sparse multivariate data obtained from geotechnical site investigation,it is impossible to identify outliers with certainty due to the distortion of statistics of geotechnical parameters caused by outliers and their associated statistical uncertainty resulted from data sparsity.This paper develops a probabilistic outlier detection method for sparse multivariate data obtained from geotechnical site investigation.The proposed approach quantifies the outlying probability of each data instance based on Mahalanobis distance and determines outliers as those data instances with outlying probabilities greater than 0.5.It tackles the distortion issue of statistics estimated from the dataset with outliers by a re-sampling technique and accounts,rationally,for the statistical uncertainty by Bayesian machine learning.Moreover,the proposed approach also suggests an exclusive method to determine outlying components of each outlier.The proposed approach is illustrated and verified using simulated and real-life dataset.It showed that the proposed approach properly identifies outliers among sparse multivariate data and their corresponding outlying components in a probabilistic manner.It can significantly reduce the masking effect(i.e.,missing some actual outliers due to the distortion of statistics by the outliers and statistical uncertainty).It also found that outliers among sparse multivariate data instances affect significantly the construction of multivariate distribution of geotechnical parameters for uncertainty quantification.This emphasizes the necessity of data cleaning process(e.g.,outlier detection)for uncertainty quantification based on geoscience data.     

Confidence level-based robust design of cantilever retaining walls in sand

Reliability-based geotechnical design entails accurate sample statistics (i.e., mean and standard deviation or coefficient of variation, denoted herein as cov) of soil parameters. However, the cov values of soil parameters are difficult to determine with confidence due to the limited availability of high-quality data and inherent spatial variability. As a result, estimated cov values of soil parameters can vary within a wide range, which can result in overdesign or underdesign. In this paper, a confidence level (CL)-based method is proposed to address the problem of geotechnical design in the face of uncertainty. Here, CL is a measure of confidence that the target reliability index will be satisfied in the face of uncertainty in the estimated cov. The proposed method is demonstrated through the design of a cantilever retaining wall in sand. To ensure the practicality of the proposed method, a simplified approach was developed, which requires little extra effort over that required for traditional reliability-based design. To develop the CL-based method further, a metric called the “true reliability index” is proposed, which is the actual reliability index in the face of the uncertainty in the estimated parameter statistics (mainly cov).     

Treatment of Loose to Medium Dense Sands by Granular Piles: Improved SPT ‘N<Subscript>1</Subscript>’ Values

The effect of granular pile installation on the modifications induced in loose to medium dense granular deposits is studied. SPT is the most often used to evaluate the in situ soil properties. Expressions for modified SPT N₁ values for different soils, i.e., for different initial SPT N₁ values, were determined as functions of replacement ratio from the available field data. Improvements in the ground are presented in the form of modified or improved SPT N₁ values versus replacement ratio charts, which can then be used to design the required degree of treatment for the expected improvement or to estimate the improved values of treated ground for different initial states of sands.     

Soil liquefaction potential induced by the andalusian earthquake of 25 December 1884

On 25 December 1884, an earthquake of epicentral intensityI ₀ = IX in the MSK scale caused great damage in a large area in the provinces of Granada and Málaga, in the south of Spain. The reports of the Spanish, Italian and French Commissions that studied the earthquake described ground phenomena in seven different sites which can be identified as soil liquefaction.By means of dynamic penetration tests carried out in the above sites, the corresponding soil profiles (based on SPT data and water table depth) were established, and the occurrence of liquefaction was proved in five out of seven of these sites. Also, the intensities at such locations and the magnitude of the earthquake were estimated.From the geotechnical data and the cyclic stress ratio induced by the earthquake, liquefaction conditions were confirmed in all the five sites which presumably liquefied. Then, possible values of the minimum ground surface accelerations necessary for the onset of liquefaction at each location were calculated. The results obtained were completed with data reported in six liquefaction case studies from Japan and the United States, from which design charts relating soil acceleration with normalized SPT values for different intensity levels were drawn.Finally, by using standard attenuation curves, the above data were translated into epicentral distances, and good agreement with the known epicentral area was found. As a result, a consistent approach for liquefaction hazard and source location problems has been developed. The proposed method combines in its formulation historical evidence and earthquake engineering techniques.     

Reliability updating in geotechnical engineering including spatial variability of soil

At geotechnical sites, deformation measurements are routinely performed during the construction process. In this paper, it is shown how information from such measurements can be utilized to update the reliability estimate of the geotechnical site at future construction stages. A recently proposed method for Bayesian updating of the reliability is successfully applied in conjunction with a stochastic nonlinear geotechnical finite element model. Therein, uncertainty in the soil material properties is modelled by non-Gaussian random fields. The structural reliability evaluations required for the Bayesian updating are carried out by means of subset simulation, an efficient adaptive Monte Carlo method. The approach is demonstrated through an application to a sheet pile wall at a deformation-sensitive geotechnical construction site.     

Geospatial contour mapping of shear wave velocity for Mumbai city

Shear wave velocity is one of the most important input parameter in the analysis of geotechnical earthquake engineering problems, particularly to estimate site-specific amplification factor and ground response study. Dynamic in situ tests such as spectral analysis of surface waves (SASW) or multichannel analysis of surface waves (MASW) are very expensive. Also due to lack of specialized personnel, these tests are generally avoided in many soil investigation programs. Worldwide, several researchers have developed correlations between the SPT ‘N’ value and shear wave velocity ‘V _s’, which are useful for determining the dynamic soil properties. In the present study, more than 400 numbers of soil borehole data were collected from various geotechnical investigation agencies, government engineering institutes and geotechnical laboratories from different parts of Mumbai city, which is financial capital of India with highest population density. In this paper, an attempt has been made to develop the correlation between the SPT ‘N’ value and shear wave velocity ‘V _s’ for various soil profile of Mumbai city and compared with other existing correlations for different cities in India. Using Geographical Information System (GIS), a geospatial contour map of shear wave velocity profile for Mumbai city is prepared with contour intervals of 25 and 50 m/s. The scarcity of database or maps of shear wave velocity profile for Mumbai city will make the present geospatial contour maps extremely useful and beneficial to the designer, practitioners for seismic hazard study involved in geotechnical earthquake engineering.     

Seismic hazard and site-specific ground motion for typical ports of Gujarat

Economic importance of major ports is well known, and if ports are located in seismically active regions, then site-specific seismic hazard studies are essential to mitigate the seismic risk of the ports. Seismic design of port sites and related structures can be accomplished in three steps that include assessment of regional seismicity, geotechnical hazards, and soil structure interaction analysis. In the present study, site-specific probabilistic seismic hazard analysis is performed to identify the seismic hazard associated with four typical port sites of Gujarat state (bounded by 20°–25.5°N and 68°–75°E) of India viz. Kandla, Mundra, Hazira, and Dahej ports. The primary aim of the study is to develop consistent seismic ground motion for the structures within the four port sites for different three levels of ground shaking, i.e., operating level earthquake (72 years return period), contingency level earthquake (CLE) (475 year return period), and maximum considered earthquake (2,475 year return period). The geotechnical characterization for each port site is carried out using available geotechnical data. Shear wave velocities of the soil profile are estimated from SPT blow counts using various empirical formulae. Seismicity of the Gujarat region is modeled through delineating the 40 fault sources based on the seismotectonic setting. The Gujarat state is divided into three regions, i.e., Kachchh, Saurashtra, and Mainland Gujarat, and regional recurrence relations are assigned in the form of Gutenberg-Richter parameters in order to calculate seismic hazard associated with each port site. The horizontal component of ground acceleration for three levels of ground shaking is estimated by using different ground motion attenuation relations (GMAR) including one country-specific GMAR for Peninsular India. Uncertainty in seismic hazard computations is handled by using logic tree approach to develop uniform hazard spectra for 5% damping which are consistent with the specified three levels of ground shaking. Using recorded acceleration time history of Bhuj 2001 earthquake as the input time motion, synthetic time histories are generated to match the developed designed response spectra to study site-specific responses of port sites during different levels of ground shaking. It is observed that the Mundra and Kandla port sites are most vulnerable sites for seismic hazard as estimated CLE ground motion is in order of 0.79 and 0.48 g for Mundra and Kandla port sites, respectively. Hazira and Dahej port sites have comparatively less hazard with estimated CLE ground motion of 0.17 and 0.11 g, respectively. The ground amplification factor is observed at all sites which ranges from 1.3 to 2.0 for the frequency range of 1.0–2.7 Hz. The obtained spectral accelerations for the three levels of ground motions and obtained transfer functions for each port sites are compared with provisions made in Indian seismic code IS:1893-Part 1 (2002). The outcome of present study is recommended for further performance-based design to evaluate the seismic response of the port structures with respect to various performance levels.     

On the estimation of scale of fluctuation in geostatistics

Describing how soil properties vary spatially is of particular importance in stochastic analyses of geotechnical problems, because spatial variability has a significant influence on local material and global geotechnical response. In particular, the scale of fluctuation θ is a key parameter in the correlation model used to represent the spatial variability of a site through a random field. It is, therefore, of fundamental importance to accurately estimate θ in order to best model the actual soil heterogeneity. In this paper, two methodologies are investigated to assess their abilities to estimate the vertical and horizontal scales of fluctuation of a particular site using in situ cone penetration test (CPT) data. The first method belongs to the family of more traditional approaches, which are based on best fitting a theoretical correlation model to available CPT data. The second method involves a new strategy which combines information from conditional random fields with the traditional approach. Both methods are applied to a case study involving the estimation of θ at three two-dimensional sections across a site and the results obtained show general agreement between the two methods, suggesting a similar level of accuracy between the new and traditional approaches. However, in order to further assess the relative accuracy of estimates provided by each method, a second numerical analysis is proposed. The results confirm the general consistency observed in the case study calculations, particularly in the vertical direction where a large amount of data are available. Interestingly, for the horizontal direction, where data are typically scarce, some additional improvement in terms of relative error is obtained with the new approach.     

Variations in shear wave velocity and soil site class in Kolkata city using regression and sensitivity analysis

The detrimental effects of an earthquake are strongly influenced by the response of soils subjected to dynamic loading. The behavior of soils under dynamic loading is governed by the dynamic soil properties such as shear wave velocity, damping characteristics and shear modulus. Worldwide, it is a common practice to obtain shear wave velocity (V _s in m/s) using the correlation with field standard penetration test (SPT) N values in the absence of sophisticated dynamic field test data. In this paper, a similar but modified advanced approach has been proposed for a major metro city of eastern India, i.e., Kolkata city (latitudes 22°20′N–23°00′N and longitudes 88°04′E–88°33′E), to obtain shear wave velocity profile and soil site classification using regression and sensitivity analyses. Extensive geotechnical borehole data from 434 boreholes located across 75 sites in the city area of 185 km² and laboratory test data providing information on the thickness of subsoil strata, SPT N values, consistency indices and percentage of fines are collected and analyzed thoroughly. A correlation between shear wave velocity (V _s) and SPT N value for various soil profiles of Kolkata city has been established by using power model of nonlinear regression analysis and compared with existing correlations for other Indian cities. The present correlations, having regression coefficients (R ²) in excess of 0.96, indicated good prediction capability. Sensitivity analysis predicts that significant influence of soil type exists in determining V _s values, for example, typical silty sand shows 30.4 % increase in magnitude of V _s as compared to silt of Kolkata city. Moreover, the soil site classification shows Class D and Class E category of soil that exists typically in Kolkata city as per NEHRP (Recommended provisions for seismic regulations for new buildings and other structures—Part 1: Provisions. Prepared by the Building Seismic Safety Council for the Federal Emergency Management Agency (Report FEMA 450), Washington, DC, 2003) guidelines and thereby highlighting the seismic vulnerability of the city. The results presented in this study can be utilized for seismic microzonation, ground response analysis and hazard assessment for Kolkata city.

     

Probabilistic and fuzzy reliability analysis of a sample slope near Aliano

Slope stability assessment is a geotechnical problem characterized by many sources of uncertainty. Some of them, e.g., are connected to the variability of soil parameters involved in the analysis. Beginning from a correct geotechnical characterization of the examined site, only a complete approach to uncertainty matter can lead to a significant result. The purpose of this paper is to demonstrate how to model data uncertainty in order to perform slope stability analysis with a good degree of significance.

Once the input data have been determined, a probabilistic stability assessment (first-order second moment and Monte Carlo analysis) is performed to obtain the variation of failure probability vs. correlation coefficient between soil parameters. A first result is the demonstration of the stability of first-order second moment (FOSM) (both with normal and lognormal distribution assumption) and Monte Carlo (MC) solutions, coming from a correct uncertainty modelling. The paper presents a simple algorithm (Fuzzy First Order Second Moment, FFOSM), which uses a fuzzy-based analysis applied to data processing.     

Effect of soil variability on the bearing capacity of clay and in slope stability problems

Site-specific geotechnical data are always random and variable in space. In the present study, a procedure for quantifying the variability in geotechnical characterization and design parameters is discussed using the site-specific cone tip resistance data (q_c) obtained from static cone penetration test (SCPT). The parameters for the spatial variability modeling of geotechnical parameters i.e. (i) existing trend function in the in situ q_c data; (ii) second moment statistics i.e. analysis of mean, variance, and auto-correlation structure of the soil strength and stiffness parameters; and (iii) inputs from the spatial correlation analysis, are utilized in the numerical modeling procedures using the finite difference numerical code FLAC 5.0. The influence of consideration of spatially variable soil parameters on the reliability-based geotechnical deign is studied for the two cases i.e. (a) bearing capacity analysis of a shallow foundation resting on a clayey soil, and (b) analysis of stability and deformation pattern of a cohesive-frictional soil slope. The study highlights the procedure for conducting a site-specific study using field test data such as SCPT in geotechnical analysis and demonstrates that a few additional computations involving soil variability provide a better insight into the role of variability in designs.     

Seismic microzonation of Bangalore,India

In the present study, an attempt has been made to evaluate the seismic hazard considering local site effects by carrying out detailed geotechnical and geophysical site characterization in Bangalore, India to develop microzonation maps. An area of 220 km², encompassing Bangalore Mahanagara Palike (BMP) has been chosen as the study area. Seismic hazard analysis and microzonation of Bangalore are addressed in three parts: in the first part, estimation of seismic hazard is done using seismotectonic and geological information. Second part deals with site characterization using geotechnical and shallow geophysical techniques. In the last part, local site effects are assessed by carrying out one-dimensional (1-D) ground response analysis (using the program SHAKE2000) using both standard penetration test (SPT) data and shear wave velocity data from multichannel analysis of surface wave (MASW) survey. Further, field experiments using microtremor studies have also been carried out for evaluation of predominant frequency of the soil columns. The same has been assessed using 1-D ground response analysis and compared with microtremor results. Further, the Seed and Idriss simplified approach has been adopted to evaluate the soil liquefaction susceptibility and liquefaction resistance assessment. Microzonation maps have been prepared with a scale of 1:20,000. The detailed methodology, along with experimental details, collated data, results and maps are presented in this paper.     

基于多源试验数据空间变异土体参数概率反演及边坡可靠度更新

岩土工程现场勘察试验通常只能获得有限的试验数据,据此难以真实地量化土体参数的空间变异性。提出了考虑土体参数空间变异性的概率反演和边坡可靠度更新方法,基于室内和现场两种不同来源的试验数据概率反演空间变异参数统计特征和更新边坡可靠度水平,并给出了计算流程。此外为合理地描述土体参数先验信息,发展了不排水抗剪强度非平稳随机场模型。最后通过不排水饱和黏土边坡算例验证了提出方法的有效性,并探讨了试验数据和钻孔位置对边坡后验失效概率的影响。结果表明：提出方法实现了空间变异土体参数概率反演与边坡可靠度更新的一体化,基于有限的多源试验数据概率反演得到的土体参数均值与试验数据非常吻合,明显降低了对参数不确定性的估计,更新的边坡可靠度水平显著增加。受土体参数空间自相关性的影响,试验数据对钻孔取样点附近区域土体参数统计特征更新的影响明显大于距离取样点较远区域。     

Performance of a steel structure on Ar-Rayyas Sabkha soils

Sabkha deposits cover extensive areas along the Red Sea and the Arabian Gulf shores. They are the site of huge industrial complexes in spite of their low bearing capacity of its upper part. The strength of the Sabkha soil is controlled by several factors, among them are the evaporatic salts that cement the grains. The Standard Penetration Test (SPT) is used extensively in this terrain but its results are misleading. The Sabkha soil that may give high N value will lose most of its strength upon wetting as part of the salts are dissolved. Therefore, the design N value was adjusted for Sabkhas to account for salt migration, by relating the SPT (N) value to the Sabkha moisture and salt content. A steel structure factory that was placed in an eastern Saudi Arabian virgin Sabkha deposits was considered. After a few years of operation fresh water leaked through the ground and caused signi.cant differential collapse settlement which threatened the functional integrity of the superstructure. The differential settlement was con.ned to one area of the structure indicating that localized conditions must have contributed to the observed settlement. The subsurface conditions and the geotechnical properties of the site are presented. A statistical model was developed that quanti.es the effect of the moisture and salt content on SPT (N) values. A simple site procedure is suggested to correct the design N value in similar cases. It was found that the increase in the moisture content could reduce the SPT (N) values by as much as 60, good agreements were found between the measured and predicted N values.     

Probabilistic comparative analysis between design rules of a shallow foundation safety

ABSTRACT

A fact that is generally overlooked in many geotechnical uncertainty analyses is that input data of the model may be correlated. While this correlation may influence the system response, epistemic uncertainties i.e. lack of knowledge of this correlation appears as a risk factor. This paper discusses how a negative correlation between cohesion (c’) and friction angle (Ø’) with their associated uncertainties can influence both the bearing resistance of a shallow strip foundation footing and the estimation of its safety. A probabilistic approach that considers both the negative correlation and the uncertainty is used in this work as a reference. This method is compared to Eurocode 7 variants that do not for the correlation. These variants, resistance and material factoring methods appears to be more or less conservative depending on the negative correlation degree between (c’–Ø), their associated uncertainties and soil configurations. Finally, the proposed probabilistic comparison shows that the material factoring method is more conservative than the resistance one.     

A performance-based framework for assessing liquefaction potential based on CPT data

This article describes a new performance-based approach for evaluating the return period of seismic soil liquefaction based on standard penetration test (SPT) and cone penetration test (CPT) data. The conventional liquefaction evaluation methods consider a single acceleration level and magnitude and these approaches fail to take into account the uncertainty in earthquake loading. The seismic hazard analysis based on the probabilistic method clearly shows that a particular acceleration value is being contributed by different magnitudes with varying probability. In the new method presented in this article, the entire range of ground shaking and the entire range of earthquake magnitude are considered and the liquefaction return period is evaluated based on the SPT and CPT data. This article explains the performance-based methodology for the liquefaction analysis – starting from probabilistic seismic hazard analysis (PSHA) for the evaluation of seismic hazard and the performance-based method to evaluate the liquefaction return period. A case study has been done for Bangalore, India, based on SPT data and converted CPT values. The comparison of results obtained from both the methods have been presented. In an area of 220 km² in Bangalore city, the site class was assessed based on large number of borehole data and 58 Multi-channel analysis of surface wave survey. Using the site class and peak acceleration at rock depth from PSHA, the peak ground acceleration at the ground surface was estimated using probabilistic approach. The liquefaction analysis was done based on 450 borehole data obtained in the study area. The results of CPT match well with the results obtained from similar analysis with SPT data.     

Uncertainty in spatial average undrained shear strength with a site-specific transformation model

ABSTRACT

Transformation models are used to infer geotechnical properties from indirect measurements. A site-specific transformation model can be calibrated with direct and indirect measurements from a site. When such a model is used, then spatial variability, measurement errors and statistical uncertainty propagate into the uncertainty of the spatial average, which is the variable of interest in most geotechnical analyses. This research shows how all components enter the total uncertainty of a transformation model for undrained shear strength from cone resistance. A method is proposed to estimate the uncertainty in the spatial average undrained shear strength, particularly focusing on the role of averaging of all spatially variable error components. The main finding is that if a considerable share of the measurement and transformation errors is random or spatially variable, the uncertainty estimates can be considerably lower compared to methods proposed earlier, and hence, characteristic values can be considerably higher.     

Site response studies in Agartala Urban agglomeration

A systematic investigation using digital microearthquake recorders with short period SS-1 seismometers, covering 76 sites in and around Agartala city, has been carried out for site response (SR) studies in the area. In the northern part of the area, SR varies from 1.15 to 1.85 corresponding to peak frequency 0.76 to 0.93 Hz where soil is mostly semi-consolidated and stiffer than recent Quaternary deposits (Haora River formation). In the southern part of the area, SR varies from 1.12 to 2.42 corresponding to peak frequency from 0.71 to 0.85 Hz within the Dupitila formation (early Quaternary). It is observed that estimated SR from H/V increases from edges to middle of the Haora River valley and impedance contrast fallows the similar trend. This reflects that site response by H/V is influenced by impedance contrast, whereas computed amplification from 1-D model shows opposite trend. The maximum amplification at fundamental frequency of resonance, 1.04 Hz estimated from H/V by near to BH-7, is 2.5 times greater than the impedance contrast/ratio derived from 1-D model for same location. Relationship between resonance frequency and depth was obtained by applying quarter wavelength and Bard (2000) methodologies, which shows linearity, whereas H/V shows its nonlinearity characteristic in soil across the valley part of Haora River. Shear wave velocities, and subsequently, SPT index and factor of safety (by cyclic stress approach) were estimated from geotechnical parameters. Vs30 and site response data were used in this study for getting a first hand information about soil stiffness condition in the area. The estimation of SPT index and factor of safety could be a useful tool for delineating liquefied and none liquefied zones at various depth levels, especially where water table exists at a very shallow level. The expected liquefiable zone was observed at depths varying from 6–25 m beneath the soil bearing zones where percentage of fines is estimated to be more than 35% for the area. This knowledge about subsurface soil characteristics will be useful for the civil engineers/city planners, which can be taken into account at the time of constructing earthquake-resistant structures in the area.     

Predicting standard penetration test N-value from cone penetration test data using artificial neural networks

Standard Penetration Test(SPT) and Cone Penetration Test(CPT) are the most frequently used field tests to estimate soil parameters for geotechnical analysis and design.Numerous soil parameters are related to the SPT N-value.In contrast,CPT is becoming more popular for site investigation and geotechnical design.Correlation of CPT data with SPT N-value is very beneficial since most of the field parameters are related to SPT N-values.A back-propagation artificial neural network(ANN) model was developed to predict the N6o-value from CPT data.Data used in this study consisted of 109 CPT-SPT pairs for sand,sandy silt,and silty sand soils.The ANN model input variables are:CPT tip resistance(q_c),effective vertical stress(σ'_v),and CPT sleeve friction(f_s).A different set of SPT-CPT data was used to check the reliability of the developed ANN model.It was shown that ANN model either under-predicted the N_(60)-value by 7-16%or over-predicted it by 7-20%.It is concluded that back-propagation neural networks is a good tool to predict N_(60)-value from CPT data with acceptable accuracy.     

Cone-penetrometer exploration of Sinkholes: Stratigraphy and soil properties

Four sinkholes with varying surficial expressions were subjected to detailed stratigraphic and soil analysis by means of Standard Penetration Tests (SPT) and Electric Friction Cone Penetration Tests (CPT) in order to evaluate applications of CPT to sinkhole investigations. Although widely used, SPT data are of limited value and difficult to apply to sinkhole mapping. CPT is sensitive to minor lithologic variability and is superior to SPT as a cost-effective technique for determining geotechnical properties of sinkholes. The effectiveness of CPT data results from the force measurements made along the sleeve of the cone. The friction ratio (ratio of sleeve to tip resistance) is a good indicator of soil stratigraphy and properties. By smoothing the friction-ratio data, general stratigraphy and changes in soil properties are easily identified. Stratigraphy of the sinks has been complicated by intense weathering, karstification and marine, transgressions. The resulting deposits include five stratigraphic units. I and II represent Plio-Pleistocene marine sediments with Unit II being the zone of soil clay accumulation. III and IV are horizons residual from Miocene strata and indicate an episode of karstification prior to deposition of Units I and II. Conduit fill is a mixture of materials with low cohesion. The fill materials indicate centripetal and downward movement of insoluble sediments derived from the surrounding strata. Loss of cohesion results in near-zero friction ratios. Very low friction ratios, coupled with materials with little cohesion, indicate potentially-liquefiable soils in the immediate vicinity of zones where piping failure may be imminent. SPT does not provide sufficient data to predict these zones of potential, failure. CPT provides sufficient information for recognition of sinkhole stratigraphy and geotechnical properties. When coupled with laboratory soil analysis, CPT provides unique information about sinkhole geometry and dynamics. In contrast, SPT data fail to produce consistent indicators of sinkhole stratigraphy or properties. With laboratory soil data, SPT indicates general, inconclusive trends.