Ground Surface Movements Research Articles

Numerical modelling of compensation grouting above shallow tunnels

This paper describes the development of a numerical model for compensation grouting which is a useful technique for the protection of surface structures from the potentially damaging movements arising from tunnel construction. Pipes are inserted into the ground between the tunnel and the overlaying structure from an access shaft. Buildings on the surface are instrumented and movements are carefully monitored. Once the deformations exceed a certain Trigger Level, grout is injected into the ground to prevent damage. In the finite element model described here, compensation grouting is modelled by applying an internal pressure to zero-thickness interface elements embedded in the mesh. An ‘observational algorithm’ is used, where the deformations of the surface are monitored and used to control the injection process. Example analyses of compensation grouting are given for three-dimensional tunnel construction underneath a greenfield site. Different strategies are used to control the injection process and their effectiveness in preventing surface movement is assessed. The numerical model is shown to replicate general behaviour expected in the field and is capable of modelling the control of ground surface movements at a greenfield site. Copyright © 2005 John Wiley & Sons, Ltd.

Engineering geology, ground surface movement and fissures induced by underground mining in the Jinchuan Nickel Mine

The Jinchuan Nickel Mine is the largest underground mine with cut-and-fill mining in China. In 1999, there appeared evident ground surface movement and many ground fissures in Jinchuan No. 2 Mine. Following an introduction to the engineering geology and mechanical properties of the rock mass in the Jinchuan mine areas, this paper reveals the features of the measured in situ stresses and puts emphasis on an analysis of the mechanism of surface movement and ground fissures induced by the underground mining with backfill. It is indicated that both the fault structures and the alteration contact zones are well developed as the dominant engineering geological characteristics in the Jinchuan mine areas. The stress redistribution in surrounding rocks resulting from the mining, the low stiffness of the filling body, the existence of the void space and the influence of on-going mining activities is the main reason for the occurrence of surface movement and ground fissures.

Circumpolar‐Active‐Layer‐Monitoring (CALM) sites in the Mackenzie Valley, northwestern Canada

AbstractActive‐layer studies have been maintained for more than a decade throughout the 1200 km length of the Mackenzie Valley. An important goal of these programmes is to monitor processes linking climate, permafrost and the active layer. Thirteen sites have been selected from these studies for the Circumpolar Active Layer Monitoring programme of the International Permafrost Association. Annual maximum thaw penetration and ground surface movements are measured relative to thaw tubes and soil temperature probes anchored in the permafrost. Active layer thickness, calculated from thaw penetration and surface movement or measured directly, varies more with local soil properties, vegetation and microclimate than with regional atmospheric climate. While depth of thaw penetration has increased at most sites for much of the record, this increase is not always reflected by a proportional increase in active layer thickness because of variable thaw settlement. Air thawing degree‐days (DDT) in the Subarctic and Boreal regions are more than double those in the Arctic regions. These increases in DDT are not reflected in active‐layer depths, suggesting the insulating effect of the surface organic layer, vegetation and snow cover on active‐layer development. Copyright © 2004 John Wiley & Sons, Ltd.

Modeling of tunneling-induced ground surface movements using stochastic medium theory

Abstract Tunneling-induced ground surface movements were modeled using the stochastic medium theory. The formulated ground movement equations were coded in a computer program, which was then used to perform back analyses of 18 ground surface settlement profiles available in the literature. Results of back analyses provided the values of two key parameters—convergence and influence angle. These two parameters are primary factors for modeling the settlement profiles. The results of the study show that the developed methodology can be used to model ground settlement profiles reasonably well for both circular and non-circular tunnels. The required input parameters can be estimated using the available information as well as empirical or semi-empirical relations. For accurate determinations of the input parameters, it is recommended that correlations between input parameters and soil/tunnel conditions be established through extensive back analyses of available field data. Also, field studies are recommended to validate the developed methodology and correlations.

Taking the soil–structure interaction into account in assessing the loading of a structure in a mining subsidence area

Underground mining of raw materials is often the cause of ground movements at the surface. Whether planned or accidental, such movements can cause considerable damage to structures located within the area of influence of underground mining works. Examples are the recent subsidences that took place at the end of the 1990s in the Lorraine iron mining field. A better understanding is necessary of how ground surface movements can be imparted to the supported structure and damage it. Indeed, it is too often considered that damage depends only on ground strain and no account has been taken of soil–structure interaction phenomena, which may affect considerably the structural behaviour. The stiffness of a structure is quantified in comparison to that of the ground as regards the various movements of the ground surface. This investigation highlights situations in which ground movements are integrally imparted to a structure. When this is not the case, the resulting complex soil–structure interaction phenomena is analysed. For this purpose, a finite-element software is used to generate models incorporating the ground material and a supported rigid structure. The ground movements are broken down into two basic movements in order to highlight the impact and the relative importance of one of these movements: ground curvature and horizontal strain. Structural stresses are quantified for different mechanical properties of the ground and the structure, as well as for different amplitudes of ground movement. This investigation made it possible to devise a methodology for analyzing structures in mining subsidence areas in order to determine cases in which soil–structure interaction phenomena must be considered. The investigation made it possible to hierarchically organize the ground and structure parameters, the variability of which has a significant effect on the behaviour of the structure affected by mining subsidence.

Centrifuge modelling of injection near tunnel lining

Centrifuge modelling was carried out to simulate the effect of compensation grouting on segmental tunnel lining and ground surface movement in dry sand. Two types of injection were investigated, namely strip injection and multi-point simultaneous injection. For strip injection, the investigated parameters are injection depth, injection distance to tunnel crown (separation), and injection width. The surface heave and lining deformation are found to follow the ratios of injection depth/injection width, and separation/injection width, respectively. To predict the ultimate uplift resistance of soil, two failure mechanisms are proposed for dense and loose sand conditions. In addition, a simple grout pressure transfer mechanism is also suggested to clarify the relationship between the maximum lining deformation and the parameters investigated. The multi-point simultaneous injection tests were conducted to investigate the effect of distributing the injection area. It was found that the sparseness of the injection points has brought beneficial effect to the surface heave and to the lining deformation. In all tests, dense sand shows dilation while loose sand undergoes compression as injected volume increases.

Observations of Ground Movements during Tunnel Construction by Slurry Shield Method at the Docklands Light Railway Lewisham Extension—East London

This paper describes monitoring results of ground movements due to slurry shield tunnelling on the Docklands Light Railway Lewisham Extension (hereinafter referred to as DLR). The DLR tunnels (twin bored tunnels) run from Island Gardens Station to Greenwich Station in East London, passing under the River Thames, a distance of around 4.2 km. The construction of the tunnels, which were at shallow depth, needed an extensive appraisal of the potential damage induced by ground movements to the overlying and underground structures. Therefore, in order to effectively minimize the ground movements, a slurry shield machine with a diameter of 5.85 m was employed. Careful control of excavation was carried out during shield tunnel construction. As a result, the slurry shield tunnelling method in Woolwich and Reading Beds by well controlled monitoring was successfully conducted, leading to volume losses less than 1.0%. This paper focuses on the ground surface movements, particularly the transverse and longitudinal settlement profiles, and volume losses during shield tunnel construction, in relation to the ground conditions. Based on the monitoring results, combined with previous centrifuge model test results and other field monitoring data, practical methods to appropriately predict ground movements due to shield tunnelling are proposed.

Side Shear Induced in Drilled Shaft by Suction Change

This paper describes an experimental study in which a 305 mm diameter instrumented drilled shaft was installed in a moderately expansive clay soil during the dry season and monitored over a period of about 15 months. The purpose of the study was to investigate the effects of seasonal moisture changes in the soil on the unit shear stresses imposed on the sides of the drilled shaft. The soil in the vicinity of the test shaft was instrumented to measure suction and ground surface movement. The relation between total suction, total stress, and shear strength of the soil at the test site was determined through laboratory triaxial compression testing. Daily rainfall and temperatures were also monitored. Over the course of the study, induced side shear stresses of up to 54 kPa were measured in the test shaft. A simple computational model was developed to relate observed suction changes to unit side shear stresses induced by the expansion of the soil through the use of the laboratory total suction-total stress-shear strength relation.

Seedling establishment patterns on the Pumice Plain, Mount St. Helens, Washington

Abstract. We examined the factors that control seedling establishment on barren substrates on the pyroclastic flows from Mount St. Helens. From June to September in 1993, we monitored seedling and microhabitat changes in 240 20 cm × 20 cm quadrats on the Pumice Plain. Seedlings emerged in 104 quadrats (43.3 %). The most abundant species were Anaphalis margaritacea, Hypochaeris radicata, Lupinus lepidus and Epilobium angustifolium. Measured site characteristics included topography, particle size distribution, ground surface movements, soil water content, organic matter, pH, and presence or absence of dead lupines. Quadrats with seedlings had higher cover of dead lupines, higher amount of rock and gravel substrate, and a greater cover of rills. More seedlings emerged where eroded material accumulated. Compared to coarse‐textured surfaces, silt surfaces had higher organic matter, held more water, and showed higher pH. However, seedlings became established more frequently on coarse‐textured surfaces. In greenhouse experiments, a higher percentage of Hypochaeris seeds germinated on silt than on sand or gravel. The germination of Anaphalis and Epilobium did not differ with soil texture, but was higher at higher moisture levels. Seedling colonization is more dependent on ground surface microtopography, particle size, and ground movement than on the chemical status of these volcanic deposits.

Vegetation recovery patterns in early volcanic succession

Permanently plots were monitored from 1983 to the present on Mount Usu after the eruptions of 1977–78 which destroyed the pre-eruption vegetation by 1–3 m thick accumulations of ash and pumice in order to clarify the processes and mechanisms of succession. Until now, 163 species were recorded in the summit area. Most of these species were derived from vegetative reproduction throughout the volcanic deposits. Vegetative reproduction plays a major role on increases in cover. Although long-distance seed-dispersal species could immigrate to the crater basin, their cover increase was slow. Seedbank species only established in gullies where the original topsoil was exposed by erosion. Most annuais were supplied by the seedbank in the original topsoil and woody species originated via immigration, suggesting that the source greatly determines the species composition of establishing vegetation. Annual seedlings showed low survival, while overwintering perennial seedlings steadily established. Ground surface movements strongly restricted increases in plant cover and the distance from source vegetation was the principal determinant of plant density. Due to differences in disturbance intensity, successional rates were higher in the stable substrates outside gullies and lower on the exposed original topsoil in some gullies.

Non-Uniform Mine Subsidence Ground Movement and Resulting Surface-Structure Damage

In recent years, a considerable amount of research has been conducted to improve the capability of engineers to predict ground-surface movements and damage to surface structures associated with underground mining. Empirical methods have shown promise in this regard, particularly in yielding estimates of ground movements. Non-uniformities in the ground movements associated with mine subsidence are not uncommon, however. The causes of these anomalies are varied and can be mining related, geology related, and surface-structure related. Ground movements normally unassociated with mine subsidence may also take place concurrently with a subsidence event. Case histories document a few of these complicating factors.

Ground surface movements due to underground excavation in the People's Republic of China : Liu Baochen, in: Comprehensive rock engineering. Vol. 4, ed J.A. Hudson, (Pergamon), 1993, pp 781–817

Ground surface movements due to underground excavation in the People's Republic of China : Liu Baochen, in: Comprehensive rock engineering. Vol. 4, ed J.A. Hudson, (Pergamon), 1993, pp 781–817

Construction of the tyne and wear metro : Tunn Tunnlg, V14, N2, March 1982, P15–18

The article reviews a discussion of tunnelling activities concerned in the construction of the Tyne and Wear metro. Tunnels and other underground structures incorporated in the network were constructed very close to buildings in Newcastle and Gateshead which in some cases required extensive underpinning works. Compressed air construction techniques were used to provide additional ground stability to reduce ground surface movements in urban areas. Ground conditions for the tunnel excavations comprised glacial deposits of boulder clay enveloping layers of sands and gravels of varying depths overlying sandstone and shale rocks of the coal measures. An extensive program of pretreatment was thus necessary in the old coal workings near Gateshead. The discussions cover construction details of the numerous individual tunnels and station excavations. (TRRL)

Regional and local networks of horizontal control, Cerro Prieto geothermal area

The Cerro Prieto geothermal area in the Mexicali Valley 30 km southeast of Mexicali, Baja California, is probably deforming due to (1) the extraction of large volumes of steam and hot water, and (2) active tectonism. Two networks of precise horizontal control were established in Mexicali Valley by the U.S. Geological Survey in 1977 – 1978 to measure both types of movement as they occur. These networks consisted of (1) a regional trilateration net brought into the mountain ranges west of the geothermal area from survey stations on an existing U.S. Geological Survey crustal-strain network north of the international border, and (2) a local net tied to stations in the regional net and encompassing the area of present and planned geothermal production. Survey lines in this net were selected to span areas of probable ground-surface movements in and around the geothermal area. Electronic distance measuring (EDM) instruments, operating with a modulated laser beam, were used to measure the distances between stations in both networks. The regional net was run using a highly precise long-range EDM instrument, helicopters for transportation of men and equipment to inaccessible stations on mountain peaks, and a fixed wing airplane flying along the line of sight. Precision of measurements with this complex long-range system approached 0–2 ppm of line length. The local net was measured with a medium-range EDM instrument requiring minimal ancillary equipment. Precision of measurements with this less complex system approached 3 ppm for the shorter line lengths. The detection and analysis of ground-surface movements resulting from tectonic strains or induced by geothermal fluid withdrawal is dependent on subsequent resurveys of these networks.