Inclinometer Data Research Articles

Reconstitution of Static Deflections of Suspension Bridge Based on Inclinometer Data

Bridge deflection is a significant index reflecting the rigidity, overall stability, carrying capacity, and seismic performance of bridge structures. However, it is difficult to measure accurately, particularly for large-span bridges with complex deflection curves. Inclinometers are tentatively used in the deflection measurements of highway and railway bridges, and they have been found to be potential high-precision deflection measurement instruments. An effective inclinometer monitoring scheme was designed and used to monitor the static deflections of bridge, and an improved data processing method was proposed through using individual analytical solutions in this study. Based on that, analysis was done to explain why the “5 inclinometers” suggested by previous research is the best choice for the deflection test of the simple supported and the continuous beam bridge, which has not explicitly explained in the previous literature. Through the comparative study of the deflection calculation results of the bridge finite element model, inclinometer is applied to measuring the static deflection of a large-span suspension bridge for the first time, and it is found when the number of the instruments is enough and arrangement of the instrument is reasonable, the deflection of suspension bridge can be tested using inclinometer method. In order to reduce the number of test points and improve the deflection measurement precision, semi-span arrangement scheme of test points is proposed, which is applied in the static deflection test of the Jiangyin Yangtze River Bridge, and the error of static deflections is only 1.13% compared to GPS observations.

Improvement of the pointing precision of the Tianma radio telescope with an inclinometer measurement system

To assure high pointing precision of the Tianma radio telescope (TMRT), new models based on a inclinometer measurement system are added to the classical pointing model. This involves four main tasks. Firstly, the inclinometer measurement system is set up and its precision is evaluated. Secondly, a feedback control strategy for pointing error for the turbulences of uneven azimuth track and thermal deformations of alidade is implemented. Thirdly, after removing the linear effect of uneven track, sine fitting inclinometer data obtains the model of nonlinear effect of azimuth-track-level unevenness. The nonlinear effect is less than ±5 arc-sec. The azimuth angles associated with large pointing error show a good agreement with those corresponding to poor track unevenness. Finally, the TMRT inclinometers monitor the effect of thermal deformations of alidade on the pointing precision of elevation from stow position, to observing almost motionless radio source, to arbitrary postures of radio telescope. The measured data after subtracting other affected factors of inclinometer including intrinsic drift, azimuth-track unevenness, variation of the center of gravity have similar tendency with the simulated results of finite element model (FEM). Applying established real-time modified model to observe the radio source 2334 + 8226, the checking results show that the pointing precision improved 65%.

CALCULATION OF STRETCHING AND BENDING STRESS IN A CASING STRING INSTALLED IN A WELL WITH A COMPLEX PROFILE

The casing column in the curvilinear well is represented as a long solid elastic rod. It has a vertically actingweight, which is evenly distributed along the length and creates variable axial tensile forces in the column body. At the same time, it is influenced by the reaction forces of the borehole walls, which, together with the weight, bend the column of initially straight pipes. It is assumed that the casing axis replicates the axis of the bent borehole, and the walls reaction is continuously distributed along the length according to a certain law, which, together with the weight, bends the column of the initially straight pipes. A system of differential equilibrium equations of internal and external forces and moments was composed. This system was supplemented to a closed form with the differential equation of curvature. This system describes large deformations of a long elastic rod in one plane. The introduction of the distributed weight, wall reactions and resistance forces into the calculation makes it non-uniform. Its feature is the need to solve the inverse problem. In this case the external load and rod deformations defined by the well shape in the form of an inclinometric data table are known. The unknown internal forces and the function of the walls reaction which creates its predetermined shape must be determined. It is established that this function depends on the distribution of axial forces caused by weight and resistance forces. As a result the system was reduced to a linear inhomogeneous differential equation with variable coefficients of the first order as to the axialforce and its solution was obtained as a sum of integrals. It is shown that one of them can be found in quadratures only in the case of a constant radius of curvature of the well. This necessitated the use of numerical integration methods. Formulas for the distribution of axial forces and bending moments in the body of the column, as well as the reactions of the walls leading the column to the actual well profile are obtained from the solution of the basic equation. To calculate these force factors, a method for numerical integration of inclinometric measurements data and software for numerical analysis of a real well are developed. This technique allows to detect the areas of local increase of the curvature and difficult passage of the curvilinear wellbore and to calculate the main parameters of the stress-strain state of the casing column in it.

Residual mechanisms and kinematics of the relict Lemeglio coastal landslide (Liguria, northwestern Italy)

The Lemeglio landslide is a deep-seated coastal landslide of the Liguria region (northeastern Italy) involving heterogeneous rock-masses formed by Miocene turbidide series, whose prevalent lithology varies from sandstones to mudrocks. It has been recognized since the end of the nineteenth century and characterized by a relict state of activity. Besides the general state of slope stability given by the current morpho-climatic conditions, different from those that determined its original paroxysmal evolution, a residual slow kinematics of the accumulation zone still exists, posing a threat to buildings and infrastructures located across the landslide foot. Consequently, the Lemeglio landslide represents a relevant case of study for advancing knowledge on residual kinematics, mechanisms and hazard inherited by a relict slope mass-movement phenomenon.The study is based on results of several drilling campaigns and geotechnical investigations carried out mainly by the Regione Liguria in the unstable landslide accumulation zone. Moreover, in this area ground deformations were assessed by inclinometer measurements and ADInSAR data covering two partially overlapping time spans, from June 2009 to July 2011 and from January 2004 to June 2014, respectively. By these data, joined with field geological and geomorphological surveys, an integrated and consistent landslide model was reconstructed, which was used for Limit Equilibrium (LEM) and Finite Elements Modelling (FEM) analyses.Among principal outcomes is the recognition, by field observations, stratigraphic and inclinometer data as well as slope stability modelling, of a basal sheared and softened band, made chiefly of remoulded mudrocks, which constrains the current landslide failure surface. Such basal band can be considered an inherited landslide structure, formed during the original paroxysmal stage of the Lemeglio landslide, which controls the current residual kinematics of the landslide deposits throughout the foot, depending also on the coastal marine erosion acting along the landslide toe.

Investigation of landslide failure mechanisms adjacent to lignite mining operations in North Bohemia (Czech Republic) through a limit equilibrium/finite element modelling approach

Understanding the impact of data uncertainty is a fundamental part of ensuring safe design of manmade excavations. Although good levels of knowledge are achievable from field investigations and experience, a natural geological environment is subject to intrinsic variability that may compromise the correct prediction of the system response to the perturbations caused by mining, with direct consequences for the stability and safety of the operations.Different types of geoscientific evidence, including geological, geomorphic, geotechnical, geomatics, and geophysical data have been used to develop and perform two-dimensional Limit Equilibrium and Finite Element Method stability analyses of a lignite open-pit mine in North Bohemia (Czech Republic) affected by recent landslides. A deterministic-probabilistic approach was adopted to investigate the effect of uncertainty of the input parameters on model response. The key factors affecting the system response were identified by specific Limit Equilibrium sensitivity analyses and studied in further detail by Finite Element probabilistic analyses and the results were compared. The work highlights that complementary use of both approaches can be recommended for routine checks of model response and interpretation of the associated results. Such an approach allows a reduction of system uncertainty and provides an improved understanding of the landslides under study. Importantly, two separate failure mechanisms have been identified from the analyses performed and verified through comparisons with inclinometer data and field observations. The results confirm that the water table level and material input parameters have the greatest influence on the stability of the slope.

Multi-sensor fusion of data for monitoring of Huangtupo landslide in the three Gorges Reservoir (China)

There hides a certain relationship among various monitoring data in a landslide, and the mining of this relationship is of significance to landslide research. In this paper, we first collect multiple monitoring data of riverside 1# slump-mass of Huangtupo landslide, the Three Gorges Reservoir Region, China, including Global Positioning System (GPS) monitoring data, inclinometer data, reservoir water level, rainfall, water content, crack width, groundwater level and temperature data, etc. By adopting the combination of quantitative statistics and qualitative simulation method for multi-sensor fusion monitoring data analysis, we overcome the one-sidedness of using a single method or single data type. The result of fusion analysis has indicated that in time periods with low rainfall or when the rainfall is not the major factor, main factors affecting landslide movement are crack development, water content of the landslide and water level of the Three Gorges Reservoir. Compared with the actual monitoring data, the fusion analysis results has a maximum error of 1.9%, which shows a good effect.

A new measurement approach for deflection monitoring of large-scale bored piles using distributed fiber sensing technology

A novel distributed fiber optic strain sensing technology, named Brillouin optical time-domain analysis (BOTDA), has been used to study the performance of large-diameter bored piles subjected to a slope excavation in Hong Kong. A new installation method for the distributed fiber optic sensors (FOS) in the bored piles was proposed in this study. Distributed strains along the instrumented bored piles were obtained by BOTDA sensors during multi-stage excavations. Details of sensor design, field installations, sensor protections, and data analysis are presented in this paper. Axial and bending strains along the instrumented pile were obtained by two sets of BOTDA sensors installed on diametrical opposite sides along the pile. The calculation method for deriving the lateral deflections from distributed strains is described. Thus, the calculated lateral deflections from BOTDA sensors were compared with the traditional inclinometers which were installed at the center of the same instrumented bored pile. Measurements obtained from the BOTDA sensors were found to be in good agreement with the inclinometer data. The maximum lateral wall deflection over the excavation depth was between 0.05% and 0.1%. The lessons learned from this field implementation are discussed and suggestions provided for further similar applications. Field application in this study reveals that the BOTDA measurement has great potential to be used for performance monitoring of large diameter piles.

Numerical simulations of landslide-stabilizing piles: a remediation project in Söke, Turkey

A catastrophic landslide following a rainy season occurred in the backyard of a school building in Soke, Turkey. The landslide caused property damage and adversely affected the present forest cover. Immediately after the landslide, double-row stabilizing piles were designed and constructed based on the findings of two-dimensional (2D) finite element (FE) analyses to take an urgent precaution. To remedy the problem, pile displacements were monitored using inclinometers, and it was observed that the measured displacements were greater than the values calculated in the design stage. Accordingly, two different three-dimensional (3D) numerical FE models were used in tandem with the inclinometer data to determine the load transfer mechanism. In the first model, numerical analyses were made to predict the pile displacements, and while the model predicted successfully the displacement of the piles constructed in the middle with reasonable accuracy, it failed for the corner piles. In the second model, the soil load transfer between piles was determined considering the sliding mass geometry, the soil arching mechanism and the group interaction between adjacent piles. The results of the second model revealed that the middle piles with large displacements transferred their loads to the corner piles with smaller displacements. The generated soil loads, perpendicular to the sliding direction, restricted pile deformations and piles with less displacement were subjected to greater loads due to the bowl-shaped landslide. A good agreement between the computed pile displacements and inclinometer data indicates that the existing soil pressure theories should be improved considering the position of the pile in the sliding mass, the depth and deformation modulus of stationary soil, the relative movement between the soil and piles and the relative movement of adjacent piles.

KINEMATIC ANALYSIS EVOLUTION OF EXTENDED LANDSLIDES: TWO CASE STUDIES FROM WESTERN GREECE

Two of the most well known historical landslide occurrences are analyzed and their temporal evolution is presented. The sites of Panagopoula and Karya are often referred as the most representative cases of long term ground displacements based on inclinometer monitoring data. Regarding these cases, the heavy rainfalls constitute the main controlling (triggering) factor, while flysch is the critical landslide-prone formation which significantly contributes to landsliding. The inclinometer data through a long time period were analyzed and typical movement diagrams were compiled. A simple statistical model including data normalization through several active stages (phases) of movement is used to identify the common kinematic features as well as to estimate the velocity trend type of movement.

Implementing the Boolean Stochastic Generation method on a 3D model of two convergent landslides

The Boolean Stochastic Generation (BoSG) method allows to generate randomly, inside an uniform soil matrix, lenses with different soil properties. In this work the algorithm to implement a BoSG simulation on a 3D model of an actual case-study is presented.In the Carnian Alps, in the Tagliamento River valley (46°23'49 N, 12°42'51 E), two adjacent landslide affect the National Road 52 Carnica. The phenomena have been studied for more than a decade allowing a detailed geological and geomorphological reconstruction to be delineated. That was done on the ground of a large number of monitoring data collected during more than 10 years of investigations. Moreover, an helicopter-borne Light Detection And Ranging (LiDAR) survey provided a 1 m Digital Terrain Model (DTM) of the area's topography. A 3D reconstruction of the slip surfaces of the landslide was created based on inclinometric data and geomorphological evidence.A specific Matlab program allowed to reconstruct the geometry of the landslide in FLAC, inserting the topography and the slip surface. The disposition of the material was randomized in one of the landslide in order to evaluate the effect of minor stratigraphic variation on the deformation pattern of the models. Results show that the variation of maximum displacement between different soil configurations is significant and that the BoSG method is an useful tool to evaluate the uncertainty associated with the soil distribution pattern inside a landslide body.

Bridge-Deflection Estimation through Inclinometer Data Considering Structural Damages

AbstractA new framework for bridge-deflection estimation through inclinometer data is presented in this paper. Whether the structure is damaged or not, deflection could be precisely estimated via the finite-element model (FEM) combined with the partial least-square regression (PLSR) method. In addition, damage localization is achieved at the same time. First, the deflection of a damaged structure is equivalent to that of an undamaged structure but subjected to special virtual loads. Second, the basis functions used in regression are calculated by the FEM of the undamaged structure rather than pure mathematical derivations. Third, the PLSR model is built on the basis of these basis functions and measured inclination data. By solving the PLSR equation, all the nodal inclinations and corresponding nodal loads of the structure could be obtained despite a limited number of measured nodes. Finally, the rotation-displacement transfer matrix is derived to reconstruct deflection from estimated inclinations, and th...

Application of electrical resistivity tomography for investigating the internal structure of a translational landslide and characterizing its groundwater circulation (Kualiangzi landslide, Southwest China)

Electrical resistivity tomography (ERT) is a widely used tool in near surface geophysical surveys for the investigation of various geological and engineering problems, including landslides. In this study, the internal structure of the southern region of the Kualiangzi landslide, which is located in Sichuan province, China, was investigated using four ERT profiles, drill cores, and inclinometer data. The characteristics of the groundwater circulation were evaluated from variations in electrical resistivity and groundwater level. The results showed that the sliding surface corresponds to a deep zone with low resistivity and that the sliding material consists of clay, gravelly soil, and weathered sandstone and mudstone. The thickness of the sliding material is 50m in the main tension trough and decreases to several meters in the direction of sliding. The dip angle of the sliding surface that has low resistivity is generally consistent with that of the bedrock. The groundwater level in the tension trough and in the middle transitional part from hill-country to flat terrain was highest in the landslide. The groundwater level close to the toe front of the landslide was the lowest. The groundwater is recharged by the precipitation and generally drains to the toe front by seasonal springs along the sliding surface. The rapid increment of the groundwater level in the tension trough kept pace with that of the displacement rate after intense rainfall. The improved understanding of internal structure and groundwater recirculation is beneficial for the analysis of the mechanisms of translational landslides and their hazard prevention.

Three‐dimensional surface deformation derived from airborne interferometric UAVSAR: Application to the Slumgullion Landslide

AbstractIn order to provide surface geodetic measurements with “landslide‐wide” spatial coverage, we develop and validate a method for the characterization of 3‐D surface deformation using the unique capabilities of the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) airborne repeat‐pass radar interferometry system. We apply our method at the well‐studied Slumgullion Landslide, which is 3.9 km long and moves persistently at rates up to ∼2 cm/day. A comparison with concurrent GPS measurements validates this method and shows that it provides reliable and accurate 3‐D surface deformation measurements. The UAVSAR‐derived vector velocity field measurements accurately capture the sharp boundaries defining previously identified kinematic units and geomorphic domains within the landslide. We acquired data across the landslide during spring and summer and identify that the landslide moves more slowly during summer except at its head, presumably in response to spatiotemporal variations in snowmelt infiltration. In order to constrain the mechanics controlling landslide motion from surface velocity measurements, we present an inversion framework for the extraction of slide thickness and basal geometry from dense 3‐D surface velocity fields. We find that the average depth of the Slumgullion Landslide is 7.5 m, several meters less than previous depth estimates. We show that by considering a viscoplastic rheology, we can derive tighter theoretical bounds on the rheological parameter relating mean horizontal flow rate to surface velocity. Using inclinometer data for slow‐moving, clay‐rich landslides across the globe, we find a consistent value for the rheological parameter of 0.85 ± 0.08.

Amendments to Interpretations of SAAF Inclinometer Data from the Furggwanghorn Rock Glacier, Turtmann Valley, Switzerland: Results from 2010 to 2012

Core Ideas Raw data from an SAAF inclinometer were processed using proprietary software. Results differed significantly from values derived using the previous software version. Direct connection between creep velocity and air and soil temperature can no longer be proposed for this specific rock glacier. Raw data processing from a ShapeAccelArray field (SAAF) inclinometer were made using proprietary software from Measurand, the manufacturer of the SAAF inclinometer. When the inclinometer data obtained from the same borehole were reprocessed with an updated software version, the results were found to differ significantly from the values derived using the previous version of software. Neither the absolute displacements, nor the curve representing displacements with depth, agreed with the previous values, despite best attempts to compare data with alternative sparse field measurements of surface displacements. There was a change in inclination of the segments above the shear zone, and the strain rates in the shear zone were reduced significantly during the winter months. In contrast, there was no change in the depth of the shear zone. Therefore, the ground model presented in the original study is still considered to be the optimal ground model of the Furggwanghorn rock glacier. Finally, a simple trigonometrical approach was conducted to investigate the validity of both software versions. The simplified recalculations could confirm mostly the results of the updated software version.

Interaction of a Railway Tunnel with a Deep Slow Landslide in Clay Shales

The Varco d’Izzo landslide system (Basilicata Region, Italy) develops at the suburbs of the city of Potenza, capital of the region, and is crossed by two transport infrastructures of local importance: the national highway Basentana and the national railway line. This paper is focused on the effects of slope movements on the railway tunnel which was built in the accumulation of an earthflow of the landslide system. The earthflow displacements were slow but continuous in the monitoring period 2005-2015 and in the order of one to several cm/year. They have led, not far from the railway tunnel area, to the eviction of a house, the dismantling of a pedestrian bridge, damages to roads and other structures. The tunnel was completely re-built in 1992 between two rows of piles, by the cut-and-cover method, after the previous tunnel had suffered severe damage due to the landslide. Available inclinometer data seem to suggest that, locally, the tunnel with its piles is hindering landslide displacements. In fact, measurements carried out in the vicinity of the tunnel, upslope from it, do not show a slip surface crossing the piles. On the other hand, landslide displacements are observed both farther, upslope from the tunnel, and downslope from it. The resultant of earth pressures acting on the tunnel is thus, probably, increasing with time. The distribution of landslide displacements around the tunnel until recent years is herein analyzed. Results of site surveys are reported. The causes of the current state of deformation of the tunnel, which was evaluated by laserscanning, are examined with the help of simplified calculations and FEM simulations.

Kinematic characteristics and dynamic mechanisms of large-scale landslides in a loess plateau: a case study for the north bank of the Baoji stream segment of the Wei River, China

The number of large-scale landslide cases along the plateau edge 98 km from the city of Baoji, China, has exceeded 68 since the 1960s. This paper describes the structure and main kinematic characteristic of two active landslides that developed in the Pleistocene Sanmen Formation, which comprises flat-lying claystone and sand deposits derived from a lake environment. In order to evaluate the risks associated with these landslides, their geometries have been reconstructed using topographic data, stratigraphic data from continuous borehole cores, and inclinometer data. The analysis of kinematic features was based on computation of geological balanced sections and deep displacement data. Laboratory tests were carried out to evaluate the changes of physical characteristics and mechanical properties in the sliding zone. The results show that the large-scale landslides were governed by a sliding zone with a clay mineral content >30 %. Furthermore, testing results indicate that a viscous flow is easily induced by the creep process, leading to plastic deformation and ultimately rapid flow.

Numerical modelling of a deep circular excavation at Abbey Mills in London

For several forthcoming tunnelling projects circular shafts will need to be constructed in London. Better understanding of their behaviour could result in more reliable movement predictions and efficient designs. A previous large-scale monitoring scheme of Thames Water's Abbey Mills shaft provided measurements of diaphragm wall deflections and bending moments. In this paper, the results of a parametric study in Flac2D are compared with the field data to understand the shaft's performance during construction. Very small wall movements are calculated and are confirmed by the inclinometer data. Previous researchers have proposed that the joints between the diaphragm wall panels reduce the circumferential wall stiffness. Out of several simulations with reduced hoop stiffness, the results obtained from the isotropic wall, that is, with strong joints, give closest agreement with the field measurements. In the initial design, the Chalk was allowed to yield below excavation level, but the field data indicate elastic behaviour. The elastic Chalk caused the wall to bend more sharply at the excavation level and hence bending moments exceeded the design predictions. Further simulations show that the wished-in-place assumption with a K0 of 1·0 in the Chalk was appropriate, and that, when the wall installation is modelled, the applied bentonite and wet concrete pressures during the construction process govern the performance of the shaft wall. These findings provide valuable information for the construction of future shafts in a similar geological setting.

Evaluation of Cervical Posture Following Rapid Maxillary Expansion: A Review of Literature

Objective:The aim of this article is to elucidate the state of the art about how rapid maxillary expansion (RME) produces changes in natural head position (NHP) in terms of cephalometric angles or inclinometer data during the growth period, according to the available literature.Methods:Electronic search was done from January 2002 to June 2012 on PubMed, Cochrane and Scopus databases; in addition manual search was conducted as well. According to keywords, eleven papers were eligible for our purpose, but definitely six papers were selected in agreement with the inclusion/exclusion criteria.Conclusions:The current literature suggests that the potential relationship between RME and NHP is still unclear. In fact, although the change in the position of the head after the rapid palatal expansion is evident clinically, current orthodontic literature does not provide conclusive evidence about the nature of this relationship

Infiltration-induced seasonally reactivated instability of a highway embankment near the Eisenhower Tunnel, Colorado, USA

Infiltration-induced landslides are major natural hazards. When they occur along highways they can impede traffic, damage infrastructure, and threaten public safety. This paper presents a case study of an active landslide on an embankment of Interstate-70 west of the Eisenhower Tunnel in central Colorado, USA. Records indicate that the hillslope under I-70 has moved episodically over the previous 40years. In the previous two decades the road surface has been displaced vertically by more than 60cm. The objective of this work is to develop a conceptual model capable of quantifying the seasonally reactivated landslide movement at the site. Inclinometer data of subsurface deformation and geologic and hydrologic mapping are used to develop the conceptual model as well as to constrain a numerical model. A two-dimensional hydro-mechanical numerical model is used to test the conceptual model under three different infiltration rates during the period of snowmelt in the spring. The framework used in the numerical model accounts for the major physical processes driving instability of the slope: time-dependent variably saturated flow, the resultant changes in stress, and induced deformation. When the snowmelt water infiltrates into the slope, the soil water content and the water-table level vary accordingly. These time-dependent variations result in changes in soil matric suction, effective stress, and consequently change in slope stability. The model calculates pore-water pressures, suction stress, and the distribution of effective stress in the embankment slope at different times. Global factors of safety as a function of time are calculated along the predetermined sliding surface using effective stresses calculated with finite elements. The slope stability assessment quantitatively confirms the conceptual model and is consistent with the displacements monitored at the site during the years of 2007–2009. It is shown that annual snowmelt infiltration of 60–100cm of water can reduce the factor of safety by 6%, enough to sustain landslide movement for as long as 8months each year.

Ground Movements due to Shallow Tunnels in Soft Ground. II: Analytical Interpretation and Prediction

This paper considers the practical application of analytical solutions for estimating ground movements caused by shallow tunneling in soft ground using closed-form expressions presented in a companion paper based on linearly elastic and average-dilation models of soil behavior. The analytical solutions express two-dimensional distributions of ground deformations as functions of three parameters: the uniform convergence and relative ovalization of a circular tunnel cavity, and either the Poisson’s ratio or the average dilation angle for elastic and plastic behavior, respectively. This paper shows that the analytical predictions can achieve very good representations of the distribution of far field deformations through a series of case studies in clays and sands. In some cases, the input parameters can be interpreted from a simple calibration to three independent measurements of ground displacements comprising surface settlements above the tunnel centerline and at a reference offset, and the lateral displacement at the spring line elevation, recorded by an inclinometer at an offset of one tunnel diameter from the centerline. However, it is generally more reliable to use a least-squares fitting method to obtain the model input parameters, using all available extensometer and inclinometer data.