Geotechnical Investigation Data Research Articles

A practical approach for modeling twin-tunnel excavation in Ho chi minh city

The prediction of ground settlement under tunnel excavation is still challenge. Almost engineer uses Mohr-Coulomb model in practice due to the conventional geotechnical investigation data. This paper describes the study of tunnel lining behaviors and ground surface settlement under tunneling process with a typical case study of twin tunnels excavation in Ho Chi Minh city, Vietnam. The advanced material model namely Hardening Soil model is used to investigate the proposing twin-tunnel with numerical approach. The internal forces of tunnel lining and ground settlement, which achieved from Hardening Soil model and the available results from Mohr-Coulomb model, are then made comparison between two models which yields some important differences for analysis. Since the experimental works for qualifying stiffness parameters in Hardening Soil model are missed in the Metro Line 1 project in Ho Chi Minh city, an empirical formula is proposed in the paper as a guide for estimating the required data in modelling process

Predictions of Geological Interface Using Relevant Vector Machine with Borehole Data

Due to the discreteness, sparsity, multidimensionality, and incompleteness of geotechnical investigation data, traditional methods cannot reasonably predict complex stratigraphic profiles, thus hindering the three-dimensional (3D) reconstruction of geological formation that is vital to the visualization and digitization of geotechnical engineering. The machine learning method of relevant vector machine (RVM) is employed in this work to predict the 3D stratigraphic profile based on limited geotechnical borehole data. The hyper-parameters of kernel functions are determined by maximizing the marginal likelihood using the particle swarm optimization algorithm. Three kinds of kernel functions are employed to investigate the prediction performance of the proposed method in both 2D analysis and 3D analysis. The 2D analysis shows that the Gauss kernel function is more suitable to deal with nonlinear problems but is more sensitive to the number of training data and it is better to use spline kernel functions for RVM model trainings when there are few geotechnical investigation data. In the 3D analysis, it is found that the prediction result of the spline kernel function is the best and the relevant vector machine model with a spline kernel function performs better in the area with a fast change in geological formation. In general, the RVM model can be used to achieve the purpose of 3D stratigraphic reconstruction.

Risk-based methodology to optimize geotechnical site investigations in tunnel projects

The scope of geotechnical investigations in tunnel projects is generally driven by the allocated resources rather than the expected variability in the ground conditions. Uncertainties in ground conditions may lead to poor decisions in project planning and active risk management. This paper presents a systematic and rational methodology to identify priority locations of additional geotechnical investigations for soft ground tunneling applications based on tunnel risks, site conditions, and project-related constraints. The methodology is applied to the cutter tool wear risk and quantifies the uncertainty in soil abrasivity index (SAI), the relevant geotechnical parameter. Preliminary geotechnical investigation data and site conditions from an actual tunnel project in an urban environment are used to illustrate the proposed methodology and demonstrate its effectiveness. Pluri-Gaussian simulation and sequential Gaussian simulation are used to characterize the 3D spatial variability in soil units and soil abrasivity, respectively, along the tunnel alignment. The study integrates geospatial assessments of SAI uncertainty and consequences of tool wear to develop an R index map that delineates the impact of uncertainty in tool wear rate. Project constraints of drilling accessibility and budget are incorporated in the R index map to find locations of additional geotechnical investigations. The study simulates a virtual sampling of additional boreholes and quantifies the reduction in uncertainty in tool wear rate and tunnel boring machine (TBM) intervention locations. Additional investigation at priority locations is found to reduce cutterhead intervention location uncertainty by approximately 90 rings (160 m). Further, integrating the uncertainty in tool travel distance is found to influence the cutterhead intervention location uncertainty by approximately 40 rings.

Utilising Land Type data for geotechnical investigations

In South Africa, a Land Type Survey (LTSS) has been conducted of the entire country. The information available from the LTSS is readily and inexpensively made available to the public (in the form of maps and accompanying memoirs). This survey includes information on the climate, terrain and soils. The soil information given includes qualitative data (such as pedological classifications, soil profiles and soil types), as well as quantitative physical and chemical properties of representative soils tested. Such information is used primarily for agricultural purposes. This paper proposes an approach for inferring information, of relevance in reconnaissance geotechnical engineering surveys, from Land Type data, to supplement geotechnical investigation data. The proposed procedure was verified using actual information from a geotechnical report. This investigation indicated that general engineering properties can be inferred from qualitative pedological data. In addition, statistically significant engineering properties (including the grading, Atterberg Limits and the USCS and AASHTO classifications) were determined from quantitative pedological data, in 86% of cases, for the soils considered. It is evident from this research that data from the Land Type survey data can be successfully used for geotechnical investigation purposes for certain developments (such as roads and townships) where the depth of interest is relatively shallow.

Design of data acquisition system for geotechnical investigation

The types of geotechnical investigation data are rich and the amount of data is huge. The traditional data acquisition method needs to consume a lot of human and material resources, and the efficiency of data acquisition is low. Based on this, the optimal design of geotechnical investigation data acquisition system is proposed. The hardware of the system adopts BS architecture and the PC adopts SSH framework, which can improve the logic control ability of the system. The software of the system realizes the synchronous acquisition of field and office work by designing the data acquisition module; Analyze the attribute and logical relationship of the collected target data, and establish a system database to reflect the dynamic process of geotechnical investigation data collection; Combined with the principle of three-dimensional imaging technology, the survey data call function of the system is designed. The test shows that this data acquisition system runs faster and the accuracy of the acquisition results is high.

Investigation and analysis of groundwater-derived damage to the Shahe ancient bridge site in Xi\u2019an, China

Earthen cultural ruins and their subsurface environments act as carriers or support for aboveground cultural heritage artefacts, and groundwater has been identified as the most important factor accelerating the destruction of ruins. In this paper, a wooden structure on the site of the Xianyang Shahe ancient bridge is taken as the research object. Through geotechnical surveys and site sample analyses, the relationship between the environment and cause of damage at the site is explored. Fluctuations in groundwater level are found to affect the movement of water and salt, thereby accelerating deterioration and allowing microbes and other soil inhabitants and plants to erode the ruins. Furthermore, strong correlations are revealed between the stratigraphy of the area and both ruin status and sample analysis results. Geotechnical investigation data are used to predict the effects of various damaging factors on long-term preservation and the underlying mechanisms and to propose feasible, long-term countermeasures for preservation studies.

Research method of comprehensive geophysical exploration for urban covered karst

During engineering investigation of covered karst in cities via conventional drilling and geophysical exploration techniques, detection accuracy is highly affected by environmental conditions. In this paper, a karst investigation on an important municipal project in Wuhan is taken as example and the clue to study geophysical exploration of municipal covered karst is proposed: engineering investigation - choose of proper geophysical exploration method - geophysical exploration - drilling confirmation. In this clue, previous geotechnical investigation data should be fully used and based on the geological conditions, petro physical parameters and investigation purpose, comparison experiment was carried out among many geophysical exploration methods and then effective geophysical exploration method was selected to reduce unnecessary work load. Moreover, drilling holes were randomly chosen for verification. It proves that the result of karst study done by geophysical exploration method from experiment comparison is relatively in accordance with the actual karst development situation. The result can provide accurate and reliable basis for engineering designs.

A Three-Dimensional Geotechnical Spatial Modeling Method for Borehole Dataset Using Optimization of Geostatistical Approaches

A large amount of geotechnical investigation data is essential for the highly reliable design of geotechnical structure at a construction site. The number of geotechnical investigations, however, has been generally insufficient and spatially biased owing to economic and spatial-temporal limitations. In this study, a geotechnical three-dimensional spatial modeling was implemented using an optimized geostatistical interpolation approach at a bridge construction site in the south-central part of the Korean peninsula. The geotechnical investigation data were collected and standardized for the construction of a geo-database. For the site-specific stratification, a kriging-based integration of the geo-layers and the seismic velocity from a seismic refraction survey were applied. The value from a standard penetration test (SPT)-N of an uninvestigated location was predicted using parametric and nonparametric geostatistical methods. We accomplished three-dimensional spatial interpolations using ordinary kriging, a sequential Gaussian simulation with a normal score transformed dataset, and a sequential indicator simulation using the geodatabase. A leave-one-out cross validation was carried out to quantitatively evaluate the reliability of the three-dimensional modeling. Finally, a three-dimensional geotechnical spatial model assigned with subsurface stratification and SPT-N values was constructed using the sequential Gaussian simulation.

Equivalent Linear and Nonlinear Site-Specific Ground Response Analysis of Pashto Cultural Museum Peshawar, Pakistan

Site-specific ground response analysis is needed for seismic hazard estimation, and its mitigation is required for seismically active regions of Pakistan. The work presented in the following includes response analysis of a specific site at Peshawar Khyber Pakhtunkhwa using equivalent linear (EL) and also nonlinear (NL) analyses. The site model was developed using the geotechnical investigation data from field investigation and subsequent laboratory tests on representative soil samples. The earthquake records compatible to the seismic activities in the target area are selected and matched to the target response spectra in order to obtain input excitation force for the base ground model. Several issues that are related to site-specific ground response analysis, i.e., shear strain, mobilized shear strength and ground acceleration along depth of soil model, are studied and compared for both EL and NL analyses. The analysis results are also further studied and compared for ground response spectra and amplification factor using both EL and NL analyses.

Study on geotechnical characteristics of marine soil at Hong Kong–Zhuhai–Macao tunnel

The Hong Kong–Zhuhai–Macao Bridge (HZMB) immersed tunnel is part of the HZMB, connecting three vibrant cities and crossing the Lingding Sea in South China. It is at the west channel of the Pearl River Estuary and the Tonggu West Channel. The stratum in this area includes deep soft soil with large differences in soil distribution. Based on geotechnical investigation data on marine soil at the HZMB tunnel, the spatial distribution of physical and mechanical properties of deposit soils was statistically analyzed. A field investigation revealed that deposit soils could be subdivided into four strata: Holocene marine deposit stratum, late Upper Pleistocene continental, mid Upper Pleistocene marine alluvial deposit, and early Upper Pleistocene alluvial deposit stratum. Field and laboratory test results indicate that Holocene marine deposit soils had a high water content (42.5% < < 81.2%), large void ratio (1.21 < < 2.43), flow-plastic state ( > 1), high compressibility ( < 5 MPa), low shear strength (2.5 kPa < < 28.5 kPa), and low bearing capacity (58.9 < < 120 kPa); therefore, they could not be used as a natural foundation. The late, mid, and early Upper Pleistocene continental deposit strata had low water content (1.5% < < 40.5%), high bearing capacity ( > 120kPa), low void ratio (0.41 < < 1.24), and low flow-plastic to liquid state ( < 0.95), Additionally, the results of regression analysis showed that the compression ratio was positively correlated with natural water content. Finding from field and laboratory tests provide a basis for immersed tunnel design and construction.

Uncertainty quantification and reduction in the characterization of subsurface stratigraphy using limited geotechnical investigation data

Subsurface stratigraphy is critical to the design, construction, and subsequent performance of geotechnical structures. However, in practice it is impossible to identify the stratigraphy of a subsurface geological domain with absolute certainty, due to the limitations imposed by geotechnical investigation techniques and project budgets. This paper presents a subsurface stratigraphic modeling and uncertainty quantification approach, which is established based on an improved and extended geological modeling technique previously established by the author and others, for simulating the stratigraphy of both two-dimensional (2D) and three-dimensional (3D) cases with more complex geological features. Furthermore, this approach provides quantitative evaluation of the amount of stratigraphic uncertainty in the current interpretation and enables the systematic reduction of stratigraphic uncertainty through the investigation of additional targeted borehole drilling locations. Illustrative examples, including artificial cases as well as two real cases from existing geotechnical projects, are presented in this study to demonstrate the use of the proposed analysis approach.

Geotechnical Investigations at the Dalian Offshore Airport, China

Based on the geotechnical investigation data of artificial island at Dalian Offshore Airport, the spatial distribution of the physical and mechanical properties of deposit soils was statistically analyzed. The field investigation revealed that the deposit soils could be subdivided into three strata, i.e., the top marine deposit stratum, middle marine-continental deposit stratum, and deep continental deposit stratum. Field and laboratory test results demonstrated that the marine deposit soils had high water content (31.2% < wn < 63.10%), large void ratio (0.88 < e0 < 1.75), low permeability (kv < 10−6 cm/s), flow-plastic state (IL > 1), under consolidated (OCR < 1), high compressibility (Es < 4 MPa), low shear strength (11.7 kPa < cu < 43.7 kPa), and low bearing capacity (0 < fak < 120 kPa), they could not be used as natural foundation. The marine-continental and continental deposits were normally consolidated to over-consolidated (OCR ≥ 1), medium compressibility (4 MPa < Es < 20 MPa), high shear strength (29.7 kPa < cu < 73.7 kPa), and high bearing capacity (fak > 120 kPa). In addition, regression analysis results showed that the compression ratio was positively correlated with the natural water content, the coefficient of vertical consolidation was negatively correlated with the plasticity index, and the coefficient of vertical permeability was positively correlated with the initial void ratio. The results of the field and laboratory tests were synthesized to provide a basis for reclamation design.

Calculation of scale of fluctuation and variance reduction function

The scale of fluctuation is one of the vital parameters for the application of random field theory to the reliability analysis of geotechnical engineering. In the present study, the fluctuation function method and weighted curve fitting method were presented to make the calculation more simple and accurate. The vertical scales of fluctuation of typical layers of Tianjin Port were calculated based on a number of engineering geotechnical investigation data, which can be guidance to other projects in this area. Meanwhile, the influences of sample interval and type of soil index on the scale of fluctuation were analyzed, according to which, the principle of determining the scale of fluctuation when the sample interval changes was defined. It can be obtained that the scale of fluctuation is the basic attribute reflecting spatial variability of soil, therefore, the scales of fluctuation calculated according to different soil indexes should be basically the same. The non-correlation distance method was improved, and the principle of determining the variance reduction function was also discussed.

Predictive analysis of stress regime and possible squeezing deformation for super-long water conveyance tunnels in Pakistan

The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hoek–Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey’s model can subsequently be employed to predict the areas’ stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai–Tibet Plateau. Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH>Sh>SV or SH>SV>Sh. The measured orientation of SH is NEE (N70.3°–89°E), and the regional orientation of SH from WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stresses of the points with the greatest burial depth were up to 56.70 and 40.14MPa, respectively, and the stresses of areas with a burial depth of greater than 500m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300m. When the burial depth is beyond 800m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.

Deep Foundations in the River Hull

Summary The River Hull Tidal Surge Barrier is located at the confluence of the rivers Hull and Humber to exclude surge tides from the river Hull and any consequent flooding from the city of Hull. This paper discusses changes to the design concept for the foundations of the Barrier necessitated by the geotechnical investigation data. Other features of the Barrier project have been described elsewhere ( Fleming et al 1980 ).