Preliminary Site Investigation Research Articles

Deep karst conduits, flooding, and sinkholes: lessons for the aggregates industry

Limestone aggregate quarries in deeply penetrating karst terrain are often at considerable risk of artesian inflow from groundwater or surface water channeled through the karstic aquifer. The inflow occurs through what are likely to be complex conduits that penetrate hundreds of feet into bedrock. Rates of inflow can exceed the operation's pumping capabilities proving to be uneconomic to manage over the long term. Over time, inflow rates can increase dramatically as turbulent flow through the conduit erodes its soft residual clay-rich fill. One recent investigation observed an inflow rate of more than 40,000 gpm from a surface water source. Floodwater persistently laden with sediment is an indicator of conduit washout and implies increasing inflow rates over time. Conduits carrying floodwater can exist in a variety of forms: along deeply penetrating geologic faults, joints, or following the path of preferentially eroded bedding. Preferential structural deformation along faults or bedding can enhance dissolution during subsequent interaction with groundwater. The resulting conduit may be a complex combination of many geological features, making the exploration and remediation of the pathway difficult. Sinkholes at the site can occur within several contexts. Pre-existing subsidence structures can reactivate and subside further, forming new collapse sinkholes within soil directly overlying the conduit. Cover-collapse sinkhole development can be a direct result of increasing downward groundwater velocities and subsurface erosion associated with the enlargement of a conduit. Normal operation events such as a quarry blast can also provide a significant new linkage between the groundwater and the quarry, allowing rapid drainage of the groundwater reservoir. With such drainage and erosion of karst-fill, sinkholes will develop over localized water table depressions, most significantly over enhanced permeability zones associated with fractures. Paradoxically, although the rise in quarry water level will lead to regional reduction in the hydraulic gradients, on local scales, drainage of the groundwater reservoir increases gradients and leads to the development of cover-collapse sinkholes. Recommended methods for preliminary site investigation can include a detailed review of geological literature and drilling logs to compile a conceptual model of the site. A fracture trace analysis with EM geophysics can confirm the locations of major faults and fractures. Fingerprinting of the various water sources to the quarry and the water in the quarry is an inexpensive and effective means of identifying the source and likely direction of the groundwater and surface water flow. Automated geophysical equipment on the market for performing rapid resistivity and microgravity surveys speeds up the site screening process during reconnaissance exploration for deep structure. It is recommended that mine planning fully incorporate this information so that quarry operators can take proactive measures to avoid catastrophic and costly flooding events.

Ground conditions and hazards: Suez City development, Egypt

Purpose Rapid engineering geological/geomorphological surveys are sometimes required for extensive urban and industrial developments on tracts of land for which little or no background topographic or geotechnical information is available. In areas unobscured by vegetation, geomorphological mapping based on air-photo interpretation augmented by field checking and detailed ground survey, can quickly provide a robust framework of terrain units of value in: planning cost-effective site investigations; interpreting and extrapolating subsurface point data provided by trial pits/ boreholes; the early identification of problematic locations requiring detailed investigation; the preliminary identification and delimitation of surface material resources; establishing a basis for preliminary assessments of ground hazard potential. The classic example of such requirements arose in the proposal to redevelop and expand dramatically the size of Suez Town (El Suweis) in the aftermath of the October 1973 Yom Kippur War. The proposed new Suez City was to be developed on 85 km 2 of desert surface that had previously been little investigated and was presumed initially to be relatively uniform and non-problematic (Fig. 1). However, preliminary site investigations revealed unexpected lateral variations in near-surface materials, thereby necessitating a rapid geomorphological survey to establish terrain conditions and to identify the potential for aggressive soils and flash-flood hazard. This was achieved by a team of five specialists in three weeks; details are to be found in Doornkamp et al . (1979), Bush et al (1980) and Cooke et al . (1982).

Investigation and remediation of chromium and nitrate groundwater contamination: Case study for an industrial facility

During a preliminary site investigation at an industrial facility (Facility) in the California desert, chromium and nitrate groundwater degradation were identified in the area of a formerly operated landfill. No currently used water supplies were identified as being affected. A groundwater extraction system was installed and operated to contain the plumes and remove contaminant mass. Based on data collected during 5 years of groundwater extraction, it was determined that contaminant reduction was not occurring. A review of disposal records for the Facility revealed that potential sources of chromium and nitrate had not been removed. A detailed field investigation of these areas was subsequently completed. The investigation included trenches, several hundred soil borings, and analysis of soil and groundwater samples. The data collected identified the location and extent of the sources of both the nitrate and chromium groundwater degradation. These sources were previously disposed chromium‐bearing kiln bricks in the landfill and undetonated blasting materials in the quarry area at the Facility. The investigation also better defined the geology, hydrology, and contaminant migration behavior. The detailed manner in which the investigation was conducted has provided the basis for the development of a revised corrective action program that coordinates contaminant source removal and ground‐water extraction. The focus of this technical article is threefold. First, the article discusses the site investigation that was conducted and the data which were collected at the Facility. The second focus is the final corrective action plan that was developed. Finally, the cost‐effective nature of the investigation and cleanup is discussed.

Drillability prediction: geological influences in hard rock drill and blast tunnelling

Usually the main subject in preliminary site investigations prior to tunnelling projects is the prediction of tunnel stability. During the past years in conventional drill and blast tunnelling, problems have occurred also connected to the accurate prediction of drillability in hard rock. The drillability is not only decisive for the wear of tools and equipment but is – along with the drilling velocity – a standard factor for the progress of excavation works. The estimation of drillability in predicted rock conditions might bear an extensive risk of costs. Therefore, an improved prediction of drilling velocity and bit wear would be desireable. The drillability of a rock mass is determined by various geological and mechanical parameters. In this report some major correlations of specific rock properties and especially geological factors with measured bit wear and drilling velocity are shown. Drilling velocity is dependent on a lot of geological parameters: Those principal parameters include jointing of rock mass, orientation of schistosity (rock anisotropy), degree of interlocking of microstructures, porosity and quality of cementation of clastic rock, degree of hydrothermal decomposition and weathering of a rock mass. Drilling bit wear increases with the equivalent quartz content. The equivalent quartz content builds the main property for the content of wear-relevant minerals. For various groups of rock types different connections with the equivalent quartz content could be detected. In sandstone bit wear is also dependent on porosity or the quality of the cementation. Finally, an investigation program is submitted, which helps to improve the estimation of rock drillability in planning future tunnel projects.

Preliminary site investigations for the new Kuala Lumpur International Airport : R. A. Nicholls, S. N. Wersching, L. T. Hock & J. A. Frame, Proceedings — ICE: Geotechnical Engineering, 119(3), 1996, pp 156–166

Preliminary site investigations for the new Kuala Lumpur International Airport : R. A. Nicholls, S. N. Wersching, L. T. Hock & J. A. Frame, Proceedings — ICE: Geotechnical Engineering, 119(3), 1996, pp 156–166

ASSIST: A COMPUTER-BASED ADVISORY SYSTEM FOR SITE INVESTIGATIONS.

Keywords HERIOT WATT UNIVERSITY SITE INVESTIGATION, COMPUTERS, SYSTEMS, ADVISORY, COMPUTER BASED, SITES, INVESTIGATIONS, PRACTICE, KNOWLEDGE BASED, PROJECTS, WATER SUPPLY, SUBSYSTEMS, DATA, ACQUISITION, METHODS, INTERPRETATION, GROUND, CONDITIONS, GEOTECHNICS, SOFTWARE, PERSONAL, SUBSURFACE, BOREHOLES, RECORDS, MODELS, CORRELATION... Show All

Thames Tunnel: geology, site investigation and geotechnical problems

A geological section of the Woolwich and Reading Beds through which the world's first subaqueous tunnel was driven (1825–43) is developed from observations made during construction by the engineer Sir Marc Isambard Brunei and his assistants. Preliminary site investigation boreholes, using a worm drill, were unsatisfactory, but a second set in 1826–27, with auger and casing tubes, gave excellent results. The project was made possible by Brunei's tunnelling shield (the first of its kind) but it could not prevent runs from a bed of sand near the top of the tunnel. With a moderately thick clay layer over the sand these caused little trouble, but where the clay cover was thin (< 6 ft) large settlements and fracture of the clay occurred, leading on five occasions to irruptions of the river into the tunnel workings. After the second irruption in 1828, there was a seven-year cessation of work while new funding arrangements were sought. Soil nailing was used in 1835 to provide additional support to the tunnel face during replacement of the old shield by a new one. Une coupe géologique des formations du Woolwich et du Reading traversées par le plus ancien tunnel sousfluvial du monde (1825–43) a été établie à partir des observations faites, lors de la construction du tunnel, par l'ingénieur Sir Marc Isambard Brunei et ses assistants. Les sondages préliminaires de reconnaissance du site, forés à la vis sans fin, n'ont pas donné grande satisfaction. Mais la seconde série de sondages (1826–27), réalisés avec une tarière et un cuvelage, a fourni de très bons résultats. Le projet est devenu réalité grâce au tun-nelier de Brunei (le premier du genre) qui n'a cependant pas pu empcher des éboulements du lit de sable situé à proximité du toit du tunnel. Là où la couche d'argile située au dessus du sable était suffisamment épaisse, les troubles induits étaient faibles. Par contre, là où la couche d'argile était mince (<6 ft), des tassements importants et des fractures sont apparus dans l'argile et ont conduit en cinq occasions à l'invasion du tunnel par la rivière. Suite à l'inondation de 1828, les travaux ont été arrêtés durant sept ans pendant lesquels de nouvelles méthodes de soutènement ont été étudiées. En 1835, un cloutage du sol a permis de renforcer le front du tunnel lors du remplacement de l'ancien tunnelier par un nouveau.

The Hydrogeochemical Characterization of Deep Groundwaters in Crystalline Bedrock: Investigations in Boreholes with Multipackers

The F inn i sh nuc lear power company , Teollisuuden Voima Oy (TVO) has been engaged for more than ten years in a survey of the Finnish bedrock aiming at the final disposal of spent nuclear fuel. The preliminary site investigations, including extensive hydrogeochemical studies (Lampen and Snellman, 1993), were performed at five sites during 1986-1992. Detailed site investigations were started in 1993 at three of the above mentioned sites: Romuvaara (migmatite banded gneiss) in northeastern Finland, Kivetty (porphyritic granodiorite) in Central Finland and Olkiluoto (migmatized mica gneiss) on the southwestern coast. The aims of the detailed hydrogeochemical site investigations are to form an extensive database of the hydrogeochemical conditions before any actual test shafts will be construced at the sites, to characterize the local hydrogeochemical conditions and to produce reliable input data for the needs of geochemical modelling and the performance assessment. Instead of sampling from deep (500-1000 m), open boreholes, groundwater samples have now been pumped from borehole sections isolated with the help of multi-packer instruments. The boreholes (KR1-KR5) have been in hydrological equilibrium for 2-3 years before the groundwater sampling. To get an overall regional hydrochemical view, precipitation, surface waters and shallow groundwaters were also sampled. This paper will discuss the presently available hydrogeochemical results from Romuvaara and Kivetty.

Comparison of interpretations of a major landslide at an earthfill dam site in Papua New Guinea

Abstract An earthfill tailings retention embankment across the Ok Ma valley in a remote tropical rainforest area of western Papua New Guinea was abandoned during construction in early 1984 because of a very large landslide that occurred in the eastern abutment of the dam. Ensuing litigation between the mine owners and their insurers brought together highly qualified and experienced geotechnical experts. The experts developed their own views on the form, nature and mechanism of the landslide which occurred in limestone colluvium and Miocene mudstone bedrock. After preliminary studies and site investigations, work for the mining company on the tailings dam was carried out as a design-and-construct package by a major consortium. Sub-sequent design investigations used most of the available techniques, including aerial photograph interpretation, seismic traverses, pitting, drilling and in situ and laboratory testing, all carried out by experienced specialist companies. Although concern was expressed on various aspects of temporary and permanent slope stability, the large size of the landslide came as an unforeseen event. This paper presents the authors' interpretation of six different models proposed for the landslide by various authorities who worked on the case. This has been done to illustrate the difficulties in attempting a precise interpretation of a large landslide and as a commentary on the state of the art on the subject.

Groundwater Control in Complex Ground Conditions

Abstract Two fifteen metre diameter ten metre deep underground tanks were constructed immediately alongside each other by sinking bolted segmental caissons and casting the secondary lining in situ . Preliminary site investigation indicated difficult ground conditions with a high risk of base failure for excavation in the dry. Wet construction of the base slab would avoid base instability but not the problem of hydrostatic uplift of the partially completed structures. Further investigation revealed a complex sequence of interbedded sands, silts and clays of alluvial and glacial origins. The granular horizons comprised a small number of thicker continuous bands, one occurring immediately below the proposed formation levels for the tank floor slabs, and several thinner irregular bands grading laterally into silts and clays. Piezometers in the more critical granular horizons indicated artesian and sub-artesian groundwater levels. Temporarily disconnecting at ground level the piezometer showing artesian conditions and measuring the resulting water flow indicated a granular body of restricted size or limited recharge. The absence of any effect on other piezometers offered confirmation of isolated granular bodies. Despite obvious difficulties in predicting the effectiveness of a groundwater lowering installation the significant advantages of constructing in the dry over wet construction mitigated in favour of dewatering. Sixteen deep pumped wells were installed around the circumference of the tanks to form a figure of eight pattern for the wells. To reduce the risk of a base failure due to artesian groundwater in any lobes of granular material encroaching within the plan excavation but not intersected by the pumped wells, four internal relief wells per tank were installed. Successful construction was achieved, although a minor interruption to the pumping clearly demonstrated the prudence of the internal relief well installation. The paper comments on some aspects of BS 5930 in relation to the construction described.

BS 5930: The Role of Geomorphological and Geological Techniques in a Preliminary Site Investigation

Abstract The recommendations for the design of a site investigation presented in BS 5930 were not found to be suitable for an investigation recently undertaken for the proposed A35 Axminster Bypass. Due to the many alternative alignments initially under consideration an investigation of all routes, involving boreholes, was not regarded as cost-effective and a programme of trial pitting and geotechnical mapping was instigated. This approach provided sufficient information for outline designs to be prepared enabling relative cost comparisons to be made between the various options and a preferred alignment to be suggested. It is proposed that amendments be made to BS 5930 to encompass the design and execution of this type of first stage site investigation and in particular to provide guidelines on the use of geotechnical mapping as a standard technique of investigation.

Surface Disposal of Waste Drilling Fluids, Ellef Ringnes Island, N.W.T. : Short-Term Observations

An experimental procedure by which waste drilling fluids were placed upon the tundra was undertaken at the Panarctic Dome et al. Hoodoo N-52 wellsite on Ellef Ringnes Island during the early winter of 1981-82. Preliminary site investigations indicated ice-rich permafrost conditions and the potential for extensive terrain disturbance if a sump were constructed. During the summer of 1982 seepage of waste effluent away from the disposal area occurred, and a quantity of muds and supernatant waters entered an adjacent creek. Water-quality analyses indicated that leaching of heavy metals was slow in the short term and soluble components were quickly diluted to background levels. The major toxicity threat posed by drilling wastes is primarily one of high salinity. The low level of terrain disturbance associated with a sumpless operations is a major advantage of such a procedure.Key words: drilling fluids, permafrost, tundra, land use regulations, terrain disturbance

The decontamination of a disused gas works site

This paper describes work carried out at a site which was to be cleared prior to its use for erection of a large retail superstore together with its adjacent car park. A preliminary site investigation indicated that contamination, especially by tar, was widespread and that numerous underground pipes and tanks were also present. During site clearance approximately 10,000 m 3 of contaminated solid material was removed and deposited in two licensed landfill sites 25 km and 40 km from the gas works. Liquid tar was adsorbed onto contaminated solids prior to disposal. A below-ground gas holder was used as a holding tank for contaminated aqueous liquids to enable suspended solids and immiscible organics to separate. After removal of contaminated material the site was covered with clean, crushed and compacted stone having known geotechnical characteristics.

Engineering geological and geophysical investigation of the Barking Creek tidal barrier site

Summary The Barking Creek tidal barrier is downstream of and complementary to the main Thames flood prevention barrier in Woolwich Reach. Preliminary site investigations included boreholes and a ‘sparker’ geophysical survey of the Creekmouth area to determine the geological structure, in particular the depth and attitude of the interface between the Thanet Sand and the Upper Chalk beneath the barrier site. Several subsequent phases of drilling at the site have allowed refinement of the original interpretation, and variations in the levels of the chalk-sand interface previously correlated with east-northeast to west-southwest trending faults are now considered to represent faults trending north-northeast. This direction is consistent with the geological structure in similar rocks determined at the Thames Barrier site 5 km upstream and elsewhere in southern England.

Engineering geomorphological investigations of a possible landslide, Killiecrankie Pass, Scotland

Summary Preliminary site investigations indicated the possible presence of a partially degraded landslide along the proposed route of the A9 Perth-Inverness Trunk Road Improvement through Killiecrankie Pass in Scotland. The steep natural topography and the congested nature of the site, with an existing trunk road and railway line, necessitated the design of relatively deep cuttings through the landslide area. To investigate the ground conditions in the area and to enable designs for the cuttings to be prepared, a programme of site investigations was implemented, consisting primarily of engineering geomorphological mapping, seismic refraction surveys and the excavation of trial trenches and pits. The investigation revealed the presence of a sequence of glacial tills, outwash deposits and ancient mudflow deposits overlying a steeply sloping and undulating rock-head. Spring sapping was identified as the only major mechanism controlling natural slope instability. Preliminary designs for the cutting slopes were proposed incorporating the need for extensive drainage of the slopes cut in the glacial deposits. This paper describes the scope of the investigations carried out, the interpretation of the ground conditions and an outline of the approach adopted towards design of the cut slopes.

Soft zones in the glacial till in downtown Edmonton: Discussion

The note by Thomson et al. is a valuable contribution likely to be much greater through the anomalous zones to the case history of Canadian glacial tills. It points out than elsewhere. A comment from the authors on this some important facts about foundation design in so-called point would be appreciated. competent glacial tills. Although their note refers to the On a recent project in Metropolitan Toronto, the Edmonton site, similar anomalous conditions have been writer has discovered anomalous till zones similar to reported by others (Adams 1960; Coates and McRostie those reported by the authors for the Edmonton tills. The 1960; Eden 1976) for other parts of Canada. Adams anomaly occurs within the Leaside till (Karrow 1967) in (1960) reported that, at a site 32 km west of Cornwall, the Borough of Scarborough at a site adjoining the the N values in the softer zones ranged between 5 and 20 Scarborough Civic Centre in the vicinity of Highway blows per 300mm in a till generally exhibiting blow 401 and McCowan Road. The till is a silty sand with counts of 50 or more. On removal from the sampling some gravel and is nonplastic. tubes, the material was reported to be . . quite soft and During a preliminary site investigation in 1977, two in many cases it slumped. The moisture content of the low N values (5-10 blows per 300 mm) in two of six softer till was reported to be high. It would be extremely boreholes were passed off as being caused by soil interesting to discover if the authors found a similar disruption7' due to drilling and sampling. In a follow-up correlation between N values and moisture content for investigation in June 1981 for the building site, anomathe 107 Street site. lously low N values were encountered in three of six In their paper, the authors predict settlements of the boreholes. Subsequently, in October-November, 1981, order of 1 10 mm for a bearing capacity of 240 kPa, a detailed investigation of the site was carried out (Mirza based on the in-situ pressuremeter testing results of the 1982) to find the extent of the anomalous zone. The softer till zones. However, earlier observations of actual additional work costing under $15 000.00, resulted in building settlements in the Edmonton area reported by savings of over $250 000.00 in projected additional DeJong and Harris (1971) indicate the field modulus of costs for piling, caisson, or raft foundations. deformation values to be significantly higher than those Because of the noncohesive nature of the till, extreme predicted by them from laboratory tests, or those care was exercised during drilling and sampling to reported later for in-situ pressuremeter tests by Eisenprevent unbalanced hydrostatic heads. Below the groundstein and Morrison (1973). Therefore, the uncorrected water level, all borings were advanced by casing and use of the in-situ pressuremeter modulus values to washboring techniques, the casing being kept full of predict the 110-mm settlement may be on the conservawater during sampling. Upon recovery, the samples of tive side. This is especially so if one postulates that the weaker silty sand till zone appeared limp, unlike the ground disturbance around the pressuremeter probe is stiff samples from the competent zones which could be lifted out in one solid cyclindrical mass from the ' ~ o t e by S. Thomson, R. L. Martin, and Z. Eisenstein. split-barrel sampler body. 1982. Canadian Geotechnical Journal, 19, pp. 175-180. Samples from both the competent and incompetent