Shallow Excavation Research Articles

Description of Timogenes pipanaco sp. nov., (Scorpiones, Bothriuridae) a new salt flat species from north western Argentina.

We describe Timogenes pipanaco sp. nov. (Scorpiones, Bothriuridae) from north western Argentina. This species is most similar to Timogenes haplochirus Maury & Roig Alsina 1977, both sharing a shallow internal excavation in pedipalp chela of males. This is the smallest known species of the genus with males averaging 33.3 mm, and is the only species of the genus with extremely reduced stridulatory organ. This species is apparently endemic to the Pipanaco salt flat in arid north western Argentina, and is active in spring. This is the first species of genus Timogenes described after 45 years.

Numerical analysis of relative density effects on shallow TBM tunnel excavation: Ground behavior and principal strains at surface in greenfield conditions

Tunnel construction in urban areas may result in ground deformations that pose a risk to existing buildings and infrastructure; thus, accurate prediction of these induced ground deformations during the design phase is crucial. The paper focuses on the effects of sandy soil relative density on the ground deformations induced by tunnels excavated with Tunnel Boring Machines (TBMs). The study utilizes the Finite Element Method (FEM) and the NorSand model to simulate the behavior of a sandy ground. The validity of the FEM modeling approach is established by comparing predictions with results from six centrifuge tunnel tests from the literature. The centrifuge tests were performed on sand at different relative densities, tunnel diameters, and tunnel depths. The parameters for the NorSand model were determined based on laboratory tests. Only the state parameter was modified to achieve the desired relative density in the numerical simulations. The effects of relative density observed in centrifuge tests (Franza et al., 2019) have been numerically reproduced with no further adjustments of the model parameters. The rich outputs from the numerical models enabled an in-depth investigation of tunnel behavior, yielding new insights into how tunnels respond under varying relative densities, depths, and diameters. A comprehensive analysis of the induced ground deformations caused by shallow tunnels in sandy ground and the potential to damage buildings is included.

Investigation on failure of deep excavations in erodible sandy strata triggered by heavy rainfall

To date, few researches have been contributed to the excavation failures frequently caused by rainstorm events featuring different rainfall patterns, especially those in erodible sandy strata. To explore the characteristics and failure mechanisms of both sloped shallow and multi-propped deep excavations in sandy strata associated with intense rainfall, this study employed a computational fluid-dynamic (CFD) and discrete-element-method (DEM) coupling method (CFD-DEM), which was validated by a typical failure of a sloped excavation triggered by heavy rainfall in China. Subsequently, extensive parametric studies were carried out to investigate the effects of rainfall amounts and patterns on the excavation responses. It was disclosed that for a sloped shallow excavation retained by soil nails, rainfall infiltration caused initial instability at the slope toe and then incurred sliding failure along a linear slip surface; regarding a multi-propped deep excavation, sand flowing failure occurred and its basal strata underwent evident upward movements, accompanied by kicking out of the embedded retaining wall. With increasing of precipitation and variation coefficient of rainfall patterns, excavation deformations increased and the rainfall-induced primary displacement zone (PDZ) expanded as well. Finally, simplified solutions were proposed to estimate the distribution of PDZ.

Deformation of Existing Shield Tunnel Adjacent to Deep Excavations: Simulation and Monitoring Analysis

Deep excavations near subway tunnels can induce deformation, necessitating a comprehensive investigation into causal factors and mitigation strategies. Field measurements were conducted to assess both vertical and horizontal displacements of existing tunnels near a deep excavation in Shenzhen. Utilizing a validated three-dimensional finite element model that considers structure−strata interactions, this study analyzes tunnel displacements, ground movements, diaphragm wall impacts and the sensitivity of enclosure structure parameters. The results indicate that tunnel deformation correlates with enclosure structure deformation, particularly near the center of the pit. Moreover, shallow soil excavation significantly affects the vertical displacement of shallow-buried tunnels. However, the design parameters of the existing enclosure structures inadequately limit tunnel displacement. Therefore, it is crucial to intensify vertical displacement monitoring in shallow tunnels during early excavation stages and to enhance horizontal displacement monitoring during later phases. Implementing measures such as optimizing central support design or retaining soil at the pit bottom helps control maximum horizontal displacement. While support stiffness plays a greater role than retaining wall thickness, its impact on deep excavation projects is limited.

Tunnel construction in shallow soft rock using the pipe shed support

In order to clarify the impact mechanism of shallow buried soft rock tunnel excavation on the upper existing highway, as well as the mechanism of pipe shed reinforcement, a combination of theoretical analysis and on-site monitoring was used to conduct in-depth research on the Diantou Tunnel Crossing the existing highway project of Dayong Expressway. The impact of shallow buried soft rock tunnel crossing construction on the existing highway and safety control issues were studied, a new deformation control index, namely deformation difference rate, was introduced. The results show that the main lateral area of influence of rock deformation is within a distance of one diameter, and the overall area of influence is within a distance of twice the diameter. From the perspective of axial tunnel deformation, the deformation of surrounding rock tends to be stable when the excavation face passes through the monitoring section about twice the tunnel diameter. Effectively controlling rock deformation depends on the total amount of settlement deformation, the change rate of deformation, and the difference rate of deformation. For V-class shallow buried tunnel surrounding rock, in order to prevent cracks on the surface, the cumulative deformation of the surrounding rock needs to be less than 50 mm, the change rate needs to be less than 3 mm/day, and the difference rate needs to be less than 5 mm/m. Finally, the proposed control standard for surface subsidence is given for similar engineering reference.

Complex Function Solution of Stratum Displacements and Stresses in Shallow Rectangular Pipe Jacking Excavation Considering the Convergence Boundary

The construction of pipe jacking has little impact on the environment and is usually used to build underground passages with shallow buried depths and short lengths. Compared with circular pipe jacking, rectangular pipe jacking has the advantages of shallow buried depth and high space utilization. Therefore, research on the excavation of rectangular pipe jacking is necessary. This paper establishes a cross-section model of shallow buried rectangular pipe jacking excavation. Taking advantage of complex functions for solving problems involving non-circular tunnels, an analytical solution is obtained using an approximate mapping function and potential functions in series forms for the stress and displacement of the stratum with a displacement condition at the excavation boundary and a stress condition at the ground surface boundary. The finite element simulation results and the engineering-measured data are used for comparisons and verifications. With the analytical solution of the complex function, the influence of selecting control points for the mapping function on the accuracy is calculated and analyzed, as well as the influence of the stratum loss rate, span, buried depth, and stratum unit weight on surface subsidence and major principal stress of the excavation boundary. The proposed analytical solution can be applied to the construction of rectangular pipe jacking tunnels.

Reasonable mechanical model on shallow tunnel excavation to eliminate displacement singularity caused by unbalanced resultant

When considering initial stress field in geomaterial, nonzero resultant of shallow tunnel excavation exists, which produces logarithmic items in complex potentials, and would further lead to a unique displacement singularity at infinity to violate geo-engineering fact in real world. The mechanical and mathematical reasons of such a unique displacement singularity in the existing mechanical models are elaborated, and a new mechanical model is subsequently proposed to eliminate this singularity by constraining far-field ground surface displacement, and the original unbalanced resultant problem is converted into an equilibrium one with mixed boundary conditions. To solve stress and displacement in the new model, the analytic continuation is applied to transform the mixed boundary conditions into a homogenerous Riemann-Hilbert problem with extra constraints, which is then solved using an approximate and iterative method with good numerical stability. The Lanczos filtering is applied to the stress and displacement solution to reduce the Gibbs phenomena caused by abrupt change of the boundary conditions along ground surface. Several numerical cases are conducted to verify the proposed mechanical model and the results strongly validate that the proposed mechanical model successfully eliminates the displacement singularity caused by unbalanced resultant with good convergence and accuracy to obtain stress and displacement for shallow tunnel excavation. A parametric investigation is subsequently conducted to study the influence of tunnel depth, lateral coefficient, and free surface range on stress and displacement distribution in geomaterial.

Innovative solution: soil cement column walls as a temporary retaining structure for excavation in soft Bangkok clay

The installation of temporary retaining walls for excavation activities is considered a crucial and costly aspect in the realm of geotechnical engineering construction. Several past studies have been undertaken on the stability aspects of the deep mixing method for soil–cement column walls in soft Bangkok clay are available. However, there has been a lack of research focusing specifically on the relationship between execution time, cost, and stability of these walls, a topic on which this study is focused. The principal aim of this research was to investigate and make a comparative analysis of the stability, construction cost, and construction duration of retaining walls under varying construction site conditions. This study placed particular emphasis on shallow excavation conducted in the context of soft Bangkok clay, and its focus was to determine the most effective construction management strategies within the given contextual parameters. The investigated wall systems comprised of soil–cement columns (SC), stiffened soil–cement columns (SSC), and sheet pile walls. The SC had a diameter of a diameter of 0.6 m, while the SSC was composed of an embedded steel pipe with a diameter of 0.2 m (SSC-IRow Wall). The stability of the walls under investigation was assessed through the utilization of finite element (FE) simulation. The finite element model was initially calibrated through a comparison between the simulation results and the data obtained from field measurements. For a 4.5 m deep excavation with a required factor of safety > 1.3, the SCC and SSCC Walls were found to have an advantage over the conventional sheet pile wall. The SC Wall, consisting of two rows and measuring 7 m in length, demonstrated superior efficiency in terms of both time and cost, regardless of whether it was implemented in unconfined or confined construction sites. The utilization of the SSC-IRow Wall was suggested as an alternative in cases where the use of a thick SC Wall was prohibited. A systematic approach for the selection and design of the SC and SSC Wall systems was proposed, drawing upon a thorough examination and evaluation of the study findings. The results of this study possess the capacity to be utilized in excavation endeavors encompassing diverse depths in the context of soft Bangkok clay and comparable soil conditions.

Description of fifty-one new species and new taxonomic arrangement for the E. sexdens group of the subgenus Edessa (Heteroptera, Pentatomidae, Edessinae, Edessa).

Within the subfamily Edessinae, Edessa Fabricius, 1803 is the genus with the most nomenclatural and taxonomic issues, basically related to the large number of poorly described species and the large number of new species. Furthermore, for many groups of morphologically similar species, certain names are used as tag names, adding to confusion and misidentification. The genus Edessa has been studied in small groups of species, either informal morphological groups within the genus or formal subgenera. Recently the nominal subgenus was revised and delimited, including the group E. sexdens. The E. sexdens group is diagnosed by a combination of characters such as anterior arms of metasternal process with excavated apex; connexival segments with a pair of dark spots; ventral surface of abdomen elevated medially; presence of a shallow rounded excavation near each spiracle; pygophore with union of dorsal rim and posterolateral angles with a groove, superior processes of the genital cup laminar, oblique to the paramere and continued ventrally by a carina; and paramere with three lobes. The biology of species in this group is almost unknown and most species have been collected in the Amazon region, particularly in the Brazilian Amazon. This group is the largest, in number of species, within the subgenus Edessa, presenting a surprising number of new species. In this article, fifty-one species new to science are described and Olbia magnifica Pirn, 1958 is transferred to Edessa. The composition of the E. sexdens group is updated to 74 species (23 previously described and 51 described here). The identification key to the species of the E. sexdens group is updated, and maps with the distribution of the new species are presented.

FIRST JURASSIC EVIDENCE OF A POSSIBLE SPINOSAURID PEDAL UNGUAL, FROM THE JAISALMER BASIN, INDIA

We describe an isolated, almost complete pedal ungual phalanx from the Middle Jurassic marine carbonate rocks of the Jaisalmer Basin, Rajasthan, north-western India. The ungual bone is triangular shaped, pointed, elongated, asymmetrical, dorsoventrally compressed, ventrally flat, bearing a shallow semi-circular excavation, and almost straight in lateral view. The morphological features, as well as its proportions closely resemble the pedal ungual phalanges of spinosaurid theropods, presently known dominantly from the Cretaceous. The affinity to spinosaurids is supported by bivariate and multivariate analyses. The ungual phalanx is tentatively identified as a basally branching Jurassic spinosaurid under Megalosauroidea. Considering the stratigraphical and geographical provenances, this contribution may represent the oldest record of a spinosaurid.

PSO-based Machine Learning Methods for Predicting Ground Surface Displacement Induced by Shallow Underground Excavation Method

Four hybrid intelligent methods are developed to predict the maximum ground surface settlement (Smax) induced by shallow underground excavation method (SUEM). Particle swarm optimization (PSO) algorithm with k-fold cross validation is used to determine the optimal hyperparameters or random parameters in the four machine learning (ML) methods, namely that, back-propagation neural network (BPNN), extreme learning machine (ELM), support vector regression (SVR) and random forest (RF). 100 field engineering samples are collected from published papers. In each data sample, the effect of stratum mechanical conditions, tunnel geometric parameters and construction parameters on Smax is considered. Correlation laws among parameters are investigated through Pearson correlation coefficient, data distribution histogram and correlation confidence ellipse. The performance of four PSO-based ML methods is comprehensively compared by fitness function, time cost and prediction accuracy in the training and test processes. PSO-RF outperforms PSO-SVR, PSO-ELM and PSO-BPNN in the prediction accuracy for Smax owing to larger R2, smaller MAE and RMSE. Calculation time that the optimal hyperparameters are determined is the fastest for PSO-RF, and PSO-ELM has the smallest fitness function. The prediction performance of PSO-RF method for construction parameters is also discussed. This work can provide theoretical guidance for design and construction of SUEM.

Influence of external insert angle on structural deformation of long pipe shed with shallow hole

The long pipe shed advanced support has the characteristics of large construction difficulty, wide support range, and easy deviation. The difference in construction dip angle will produce a different plastic zone of surrounding rock and supporting effects, and the rationality of advanced support design plays an important role in the safety of tunnel opening excavation. Based on the Tianshan Tunnel project, this paper aims at the problems of the loose pebble layer structure, poor cohesion, strong permeability, shallow excavation is not easy to form a confined arch, and easy to causes surrounding rock deformation and failure. Combined with the new method theory, the finite difference software FLAC3D was used to simulate seven excavation schemes of the shallow tunnel entrances. The mechanism and effect of advance support and the influence of construction angle on support effect are analyzed, and the simulation values are compared with the measured data. The results show that using long pipe shed advanced support can effectively reduce the disturbance of excavation to lose pebble rock mass and reduce the convergence value of surrounding rock. The plastic zone of surrounding rock produced by different angles can be divided into three parts. The structural stability difference of the C1 zone is small, and that of the C3 zone is large. The bending moment, shear force, and shape variables of the pipe shed decrease with the increase of the dip angle, while the axial force increases with the increase of the dip angle. According to the similarity between the simulated curve and the measured curve, the best supporting effect can be achieved when the dip angle of the pre-supporting pipe shed is set in the range of 0° ~ 3°.

Late Quaternary Activity Studies on the Lintong–Chang’an Fault Zone in the Weihe Graben, Central China, Using Combined Techniques

The Lintong–Chang’an Fault Zone (LCFZ) is an important active structure in the Weihe Graben (central China). The study on the activity of the LCFZ is not only of great significance to explore the regional tectonic mechanism, but also has practical value in urban seismic mitigation and disaster relief. In this study, based on high-resolution remotely sensed imagery, shallow seismic reflection survey, borehole data and excavation of a foundation pit, we determined the distribution and activity of the Wangjiabian–Houjiawan fault (a branch fault of the LCFZ) in the Shaoling Loess Tableland. Combined with previous studies, we further inferred that the vertical displacements were 0–6 m along the LCFZ, but most displacements were around 1 m. Furthermore, there are eight locations where no displacements have been found in the Late Pleistocene strata. The offsets on the fault zone since the Late Pleistocene display a wave-like pattern, which is unrelated to the regional topographic expression. Compared to other faults in the Weihe Graben, the activity of the LCFZ in vertical component is relatively weak, implying a possible strike–slip motion. In addition, a major active fault may exist on the northwest side of this fault zone, bearing part of the fault motion in this region.

A study on the factors influencing the development of the thinking and politics of higher education courses in China based on the “O2O” model

Abstract The outbreak of novel coronavirus pneumonia in early 2020 has attracted more and more attention to the O2O teaching mode to implement the deployment of “stopping classes without teaching and learning” during epidemic prevention and control. In this paper, we take the factors influencing the development of curriculum thinking politics in the continuing education of higher education as the object and use the Bayesian network to apply the influence indicators of curriculum thinking politics to complex scenarios for causal inference to explore the development path of curriculum thinking politics in the continuing education of higher education. According to the analysis of 1205 questionnaires of adult education, 49.95% of the students think that the concept of education has the problem of “understanding but not depth”, 61.41% of the students think that the content of curriculum thinking and political education has “shallow excavation but little integration”, and 51.96% of the students think that the teaching concept has “shallow excavation but little integration”. 51.96% of the participants think that the teaching method is “traditional and less interactive”, and 38.05% of the participants think that the evaluation of education is “professional but not political”, which are the four key factors that affect the development of the course of higher education in China. This paper proposes improvement methods through the four key factors of the development of the course of thinking and politics so that the students can receive knowledge and understand the ideological and political education at the same time and naturally build up their moral character, which can achieve the effect of “embellishment”.

UAV Image-Based Plan Drawing Method in Submerged Terrestrial Archaeological Settlements: The case of Kibotos

Documentation with drawing and photography is one of the most important stages in archaeological excavations and surveys. It takes a long time to draw walls by stone by stone during the excavations. Carrying out these studies on land that does not belong to human habitats, such as underwater, is an activity that requires extra effort, time, and experience. This article will examine the possibility of drawing the plans of the structures unearthed or detected in the archaeological underwater excavations and surface surveys in shallow waters with the help of aerial photographs in a shorter time and with less effort. The research results show that the photograph-based archaeological plan drawing is an excellent and suitable method for shallow water archaeological excavation and surveys. It reveals that it can save time and labour in surveys and rescue excavations where time is limited.

Influence of Tunnel Excavation on the Deformation of a Frame Building

Tunnel excavation inevitably causes surface deformation. In urban areas, surface deformation could lead to the deformation of surrounding buildings, which may cause damage to communities when accumulated to a certain extent. However, the current construction organization and management mainly rely on on-site deformation measurements, and there is still a lack of reliable prediction methods. Here, we proposed an effective evaluation method for frame building deformation based on the stochastic medium theory and the equivalent beam theory. This method could effectively evaluate the surface and building deformation after a horseshoe tunnel excavation by considering the non-uniform convergence. Furthermore, its accuracy and practicability were verified using the Nanyan Fourth Circuit Transmission Reconstruction located in Dalian, China. The results show that the spatial distribution and characteristic values of the maximum tensile strains were closely related to the ratio of Young’s modulus to the shear modulus (E/G), the building height (h), the tunnel depth (H), the tangent of the tunnel influence angle (tan β) and the convergence radius (ΔR). These achievements can provide a theoretical basis and analytical ideas for investigating the influence of shallow buried tunnel excavation on frame structure buildings in cities.

Field test and numerical simulation of ground settlement in super shallow buried station excavation supported by transverse pipe roof

The pipe roof is an effective means to control the surface settlement during the construction of the super-shallow buried subway station. The transverse pipe roof method can not only reduce the construction work surface, but also improve the construction efficiency by multi-stage flow construction. Based on the transfer station project of the Olympic Sports Center of Jinan Rail Transit Line 3, the ground settlement law caused by the excavation of ultra-shallow buried subway station under the action of transverse pipe roof is analyzed through field measurement. The mechanism of pipe roof controlling ground settlement and the influence of steel pipe spacing and steel pipe length on the bearing mechanism of pipe roof are analyzed by numerical simulation. The following conclusions are drawn. 1) The surface settlement curve caused by the excavation of the small pilot tunnel in the lateral direction of the station is a wavy U-shaped, and the surface settlement curve becomes a smooth U-shaped after the soil is broken. In the longitudinal direction of the station, the surface settlement is jagged, and the surface settlement above the pipe roof is less than the surface settlement between the pipe roofs. 2) After soil excavation, pipe roof can bear the load of surrounding rock and restrain the settlement of soil above, and soil arch effect is formed between pipes to restrain the relaxation of soil between pipes. With the increase of the spacing of the steel pipe, the height of the soil arch increases. After exceeding a certain spacing, the micro-soil arching effect disappears and the surface settlement increases. 3) The length and stiffness of pipe roof will affect the bearing capacity of pipe roof and there is an upper limit. When it exceeds the upper limit, increasing the length or stiffness of pipe roof has little effect on the control effect of ground settlement. The research can provide reference for shallow buried excavation station and other projects.

Diagnose of the nominal subgenus of Edessa and description<br>of the E. sexdens group (Heteroptera, Pentatomidae, Edessinae)

The subgenus Edessa, the largest and to date the most confusing taxon of Edessa is diagnosed here, comprising 79 species listed in this work. The subgenus is characterized by the humeral angles conical, somewhat developed, and projected, with apex rounded or somewhat acuminated, but never acute, shyny and impunctate or with a few punctures. The E. sexdens group, composed of 22 species, is proposed here to the subgenus Edessa. This group can be characterized by the anterior arms of the metasternal process with excavated apex; connexival segments with a pair of dark spots; ventral side of the abdomen raised medially; rounded shallow excavation near each spiracle; area between dorsal rim of the pygophore and posterolateral angles grooved; superior process of the genital cup laminar and continued ventrally by a carina, oblique to the parameres; parameres with three lobes; area between dorsal rim of the pygophore and posterolateral angles grooved. The species of the E. sexdens group are distributed in the Neotropical region, from Mexico to Argentina. Descriptions, measurements, and illustrations are provided. An identification key and distributional map are presented. The species Edessa suturata Dallas, 1851 is considered junior synonym of E. alces Erichson, 1848; E. inclyta Walker, 1868, E. fuscidorsata Distant, 1881, and E. gnu Breddin, 1905 are considered junior synonyms of E. electa Walker, 1868; E. olivacea Stål, 1862 and E. ventralis Walker, 1868 are considered junior synonym of E. phoenicopus Dallas, 1851; E. nigromarginata Distant, 1881 is considered junior synonym of E. sexdens Fabricius, 1803; E. subandina Breddin, 1994 is considered a valid species; Edessa dentata (Dallas, 1851) and Edessa excellens (Walker, 1868) are considered junior synonym of E. (E.) urus Erichson, 1848.

Novel hybrid method to predict the ground-displacement field caused by shallow tunnel excavation

Novel hybrid method to predict the ground-displacement field caused by shallow tunnel excavation

A case study on performances of overlying pipelines due to shallow tunnels excavation in water-rich gravel ground

Twin rectangular-shaped tunnels were constructed vertically beneath the adjacent pipelines in water-rich gravel ground. An analysis was carried out using measured datum to reveal the response of the overlying pipelines to the construction of shallow tunnels. The method of superposition was applied for describing the displacement profile of the overlying pipelines. The transverse profile shapes for the pipelines remain different. The profile of the gas pipeline and box culvert firstly displays a single-trough “n” shape and “U” shape, respectively, whereas the final profile of the pipelines displays an unsymmetrical double-trough “W” shape. It is also found that the safety of the existing pipelines was generally ensured, except for one monitoring point of the box culvert on the right side of the shallow tunnel. It implies that the larger grouting thickness beyond the excavated outline of the shallow tunnel should be conducted in similar cases.