Excavation Costs Research Articles

Optimum Design of Lined Channel Sections

The channel design problem can be treated as an optimization problem in which the objective function is minimization of construction cost. In this definition, the optimum values of section variables, i.e. side slope, bottom width, flow depth and radius, can be computed by minimizing the total cost subjected to a hydraulic flow constraint formula, i.e. the Manning’s equation. In a general scope, the total cost comprises lining, earthwork cost and the additional excavation cost accounting for the depth of earthwork under the ground surface. In this paper, a novel optimization technique, invariably called the Modified Honey Bee Mating Optimization (MHBMO) algorithm, was utilized to solved the defined design problem. By investigation of the affection of different cost values on the optimal results, a new explicit model for common channel shapes, i.e. triangular, rectangular, trapezoidal and circular, was proposed utilizing the MHBMO algorithm to directly design the channel cross sections. The proposed model was compared to the present models in literature using four design examples. The results demonstrate that, despite of simplicity of the new model, it achieves more precise values than the present models for all common channel shapes.

Bi-level Drainage System Design considering Upward Leakage from Semi-impermeable Barrier

Bi-level drainage system, in which alternate shallow and deep subsurface drains are laid, seems to be an economical option as compared to the level drainage system due to substantial reduction in cost of excavation. Mathematical solutions are available to describe fall of water table between two bi-level drains located at some distance above the horizontal impermeable barrier. But, if the barrier is semi-impermeable, little information is available to account for the vertical upward leakage in the soil system and its effect on spacing, fall of water table and discharge of drains. In the present study, a boundary value problem consisting of one dimensional linearized Boussinesq equation incorporating vertical upward leakage from semi-impermeable barrier with appropriate initial and boundary conditions was formulated. Analytical solution of such linearized equation has been obtained after devising a simple transformation through which boundary value problem was transformed to a heat transfer problem for which a solution was available. Spatial and temporal variation of water table between two bi-level drains was obtained employing this solution. A special case of the proposed solution (without vertical leakage) was verified with the existing solution and identical values of water table heights were obtained. The effect of hydraulic resistance of semi-impermeable barrier on spacing, water table heights between two bi-level and level drains and discharge of drains was studied by considering a numerical example based on assumed and experimental data. It was observed that with increase in the value of hydraulic resistance the spacing and fall of water table between two drains increases. Discharge of the drains is also influenced due to vertical upward leakage. An increase in hydraulic resistance, discharge of the drain decreases. The solution can be employed to determine discharge, spacing and fall of water table between two level or bi-level subsurface drains considering the semi impermeable barrier.

Soil-buried pipeline interaction for vertical downwards relative offset

A new perspective is presented on the interaction effects for the vertical downwards offset of a pipeline relative to its surrounding soil. Instead of estimating the interaction force via shallow footing bearing capacity theory, as per common pipeline design practice, we assume that the vertical movement of the pipeline in uniform soil is governed by mechanisms similar to the lateral loading of a circular pile up to its limit load. The validity of this assumption is investigated numerically with the finite element limit analysis method, and design expressions are derived for the maximum interaction force on pipelines embedded in cohesive and granular soils. For the common case of buried pipelines built in sand-backfilled trenches, the same numerical method is employed to determine the necessary trench dimensions so as to avoid interaction with the possibly much stiffer native soil that results in a significant increase in the force applied on the pipeline during ground movement. The described approach can be employed in project-specific analyses to optimize trench dimensions, and thus avoid unnecessary excavation costs or mitigation measures.

Deep enclosures versus pumping to reduce settlements during shaft excavations

Deep excavations in aquifers may be constructed by combining pumping with the cut and cover method. The enclosures are often deepened more than structurally needed, in order to diminish the risk of heave or fluidisation inside the excavation, and to reduce pumping rates and the associated settlements outside jet-grouting piles are sometimes adopted for lengthening.We analysed the water-proofing efficiency of jet-grouting and the need for water isolation in preconsolidated sediments. We used data obtained from two shaft excavations during the construction of the high speed train tunnel in Barcelona, located adjacent to the Sagrada Familia Basilica. Jet-grouting was characterised using pumping tests before and after the construction of the enclosure. The effectiveness of deepened enclosures was evaluated by comparing settlements caused and discharges required for several dewatering scenarios. Differences between them lie in the depth of the enclosures. Settlements were calculated analytically, using the drawdown obtained from a hydrogeological model, and numerically employing a hydro-mechanical model.Results show that jet-grouting reduced the permeability of the soil (90% reduction, from 5.5 to 0.6m/d). However, this reduction only affected the pile area, so that the necessary pumping rate and the settlements outside the enclosure were only reduced by 40%. Results also show that settlements due to groundwater pumping are fairly smooth (i.e., differential settlements are small) with low absolute values. Moreover, they recover when pumping ceases. This rather elastic and stiff behaviour reflects the preconsolidated nature of the sediments in Barcelona and the fact that drawdowns concentrate at depth, where the soil is most compact, causing little change in effective stress near the soil surface. Under these conditions, pumping does not pose a serious risk to settlements, and excavation costs can be lowered by constructing the enclosure at the minimum depth required structurally. Also, an intense control of the pumping process may help reducing the conventional safety factors against heave.

Energetic cost of digging behavior in workers of the leaf-cutting ant Atta sexdens (Fabricius)

Energetic cost of digging behavior in workers of the leaf-cutting ant Atta sexdens (Fabricius). During nest excavation, leaf-cutting ant workers undergo reduction in their body reserve, particularly carbohydrates. In order to estimate the energetic cost of digging, groups of 30 workers of the leaf-cutting ant Atta sexdens were sealed in a hermetic chamber for 24, 48 and 72 hours, with and without soil for digging, and had the CO2 concentration measured using respirometric chambers as well as volume of soil excavated (g). As expected, the worker groups that carried out soil excavation expelled more carbon dioxide than the groups that did not excavate. Therefore, a worker with body mass of 9.65 ± 1.50 mg dug in average 0.85 ± 0.27 g of soil for 24 hours, consuming ca. 0.58 ± 0.23 J. In this study, we calculate that the energetic cost of excavation per worker per day in the experimental set-up was ca. 0.58 J.

2아치 터널 굴착 공법과의 비교를 통한 주방식 굴착 공법의 예비 경제성 검토 연구

ABSTRACT: This study aims to investigate an economical efficiency of two excavation methods with respect to the room-and-pillar method for the underground space and conventional excavation method, i.e. 2-arch tunnelling method. For feasibility study, an excavation cost for both room-and-pillar method and 2-arch tunnelling method was estimated when the same space in operation was required. It was assumed that properties of reinforcements and rock were adopted from literatures. However, an excavation shape of the room-and-pillar method was assumed not to be the rectangular shape which is a general type in the room-and-pillar method but to be an arch shape in order to compare with the conventional excavation method (2-arch tunnelling) and to achieve the maximum bearing capacity of the structure during excavation. Consequently, the wider space in use or required and the better condition of rock we assumed, the more economical advantage we have in the room-and-pillar method than the 2-arch tunnelling method.Keywords: Room and pillar method, Rock pillar, Economical efficiency, 2-arch tunnel, Excavation

Assessing the construction cost of Greek transportation tunnel projects

Cost estimation is a crucial factor for the success of an engineering project. This element is even more important at the initial stages of design where decisions should be taken based on the more accurately available cost data. In underground construction projects especially, where the variability of the geotechnical conditions can change initial estimates, the accurate estimation of the construction cost from the preliminary phases of the project can minimize cost overrun issues as well construction claims and disputes. The purpose of this paper is to provide insight in cost estimation for underground projects focusing on tunnels. For this reason, the analysis of construction cost is undertaken, based on data from a set of 9 tunnels that have been constructed in Greece. The analysis presented focuses on the excavation and temporary support cost with respect to the geotechnical conditions encountered. Although the cost is influenced by many parameters, through the analysis of past data using the Case Base Reasoning approach, valuable lessons can be learned by decoding the effect of the ground conditions on the construction cost. The construction cost of the Greek tunnels is estimated for 2011 price levels and it is expressed though range estimation for 5 rock mass categories that were identified. Furthermore, a direct linkage between construction cost and the encountered geotechnical conditions, as expressed in GSI values, are made in an attempt to capture the general trend of construction cost in terms of €/m3 and €/m. The findings can be used as a first order assessment in order to have a representative estimation of the tunneling cost from the initial stages of project design.

Evolution of repository and waste package designs for Yucca Mountain disposal system for spent nuclear fuel and high-level radioactive waste

This paper summarizes the evolution of the engineered barrier design for the proposed Yucca Mountain disposal system. Initially, the underground facility used a fairly standard panel and drift layout excavated mostly by drilling and blasting. By 1993, the layout of the underground facility was changed to accommodate construction by a tunnel boring machine. Placement of the repository in unsaturated zone permitted an extended period without backfilling; placement of the waste package in an open drift permitted use of much larger, and thus hotter packages. Hence in 1994, the underground facility design switched from floor emplacement of waste in small, single walled stainless steel or nickel alloy containers to in-drift emplacement of waste in large, double-walled containers. By 2000, the outer layer was a high nickel alloy for corrosion resistance and the inner layer was stainless steel for structural strength. Use of large packages facilitated receipt and disposal of high volumes of spent nuclear fuel. In addition, in-drift package placement saved excavation costs. Options considered for in-drift emplacement included different heat loads and use of backfill. To avoid dripping on the package during the thermal period and the possibility of localized corrosion, titanium drip shields were added for the disposal drifts by 2000. In addition, a handling canister, sealed at the reactor to eliminate further handling of bare fuel assemblies, was evaluated and eventually adopted in 2006. Finally, staged development of the underground layout was adopted to more readily adjust to changes in waste forms and Congressional funding.

Review and assessment of the NTNU/SINTEF Soil Abrasion Test (SAT™) for determination of abrasiveness of soil and soft ground

Measuring soil abrasivity for excavation tool life estimation, is becoming more necessary as tunnels are longer and with limited access to execute interventions and tool changes from shafts. The tool life is a major contributor to the tunnel excavation costs and tunnelling progress. The aim of this paper is to explain the consequences of tunnelling in abrasive soil and soft ground conditions, and explain the NTNU/SINTEF Soil Abrasion Test™ (SAT) which is one approach to measure soil abrasivity. In this paper a total of 254 different soil samples (clay, silt, sand and gravel are represented) originating from 8 different countries have been tested and included in the discussion of the SAT™ procedure’s applicability. Further, the paper relates the SAT™ test values to commonly known tribological theories regarding abrasion as well as presenting trends and correlations between the measured SAT™ value and measured scraper, ripper and disc cutter life from a total of nine completed TBM/pipe jacking projects, excavated with slurry shield face support.

Case study: Risk analysis by overtopping of diversion works during dam construction: The La Yesca hydroelectric project, Mexico

A risk analysis-based methodology for the determination of the most economical layout dam–tunnel diversion works is introduced. The aim of the proposed procedure is to identify the least cost layout in terms of the diversion works overtopping risk. The methodology has been built upon the reliability theory advanced first-order second moment approach, and accounts for the probability of the maximum height reached by the upstream water elevation, associated with a design flood (as characterized by its return period), as well as for excavation and lining costs. The proposed procedure has been applied to the La Yesca hydroelectric project in Mexico, currently under operation. It is demonstrated that the use of composite roughness, which consists of lining the floor of the diversion tunnels with hydraulic concrete, while the walls and vault of the tunnels are lined with shotcrete, results in an increase in the discharge capacity of the tunnels, thus leading to a reduction of the overall risk of the project. The importance of economic risk assessments is emphasized and the flexibility of the proposed methodology to account for a suite of risk–cost combinations is shown.

Roadside Clearance Limit on Horizontal Curves with Transition Arcs

AASHTO guidelines for the geometric design of highways require that the insides of horizontal curves be clear of sight obstructions to provide required sight distance. However, the guideline's method for determining minimum roadside clearance is suitable only for middle sections of horizontal curves at sites where the circular arcs are equal to or longer than sight distance. For other sites and sections of horizontal curves, the guideline recommends the use of graphical or computational methods. The graphical method is tedious and time-consuming, and the recommended computational method was prepared for sites with circular arcs equal to or longer than sight distance. An analytical model was developed for clearance offsets for sites with circular arcs shorter than sight distance. Offsets were defined as normal ordinates from the driver path to a curve that demarcates the roadside area that accommodates sightlines. Variables in the model are sight distance, length of transition, length of circular curve, radius of circular curve, and driver location. Design charts for maximum and intermediate offsets were developed for use by practitioners with the model. Offsets from the charts for curves that have transition arcs were significantly shorter than offsets for equivalent simple curves. With these charts, the extra excavation costs associated with the resultant bigger offsets of other models can be avoided. Study results will be of value to engineers involved in design policy, highway maintenance, and design improvement for sites with insufficient sight distance.

Minimum Cost Design of Irrigation Canals Using Probabilistic Global Search Lausanne

Cost-effective design of irrigation canals is essential for the planning and management of irrigation projects. In this study, the minimum cost design of irrigation canals is performed by considering the excavation cost, lining cost, cost for water losses and land acquisition cost. The complex non-linear and non-convex optimization model of irrigation canal design is solved using a recently developed meta-heuristic tool, namely probabilistic global search Lausanne (PGSL). The solutions are found to be competent with those reported based on classical procedures while applied for an example problem. To suit for real field applications, two site-specific constraints are added to the model for the optimal design of trapezoidal canals. The study shows the potential of the proposed PGSL approach to perform comprehensive design of irrigation canals.

Excavation Technology of Shield Tunneling in Mixed Ground

The excavation technology of shield tunneling in mixed ground is described in this paper. The interval metro tunnel is 2004 m long and 8.5 ~ 25 m deep below the ground surface. The 511 m long tunnel is located in the mixed ground. Especialy the upper of tunnel is soil and the lower of tunnel is rock. In order to improve the excavation advance and reduce the excavation cost by shield method, the tunneling mode, excavation parameters, cutter change, construction organization and management are adopted according to the ground properties. The excavation technology is successfully applied and provides a good reference for the similar ground conditions.

Applications of NTNU/SINTEF Drillability Indices in Hard Rock Tunneling

Drillability indices, i.e., the Drilling Rate Index™ (DRI), Bit Wear Index™ (BWI), Cutter Life Index™ (CLI), and Vickers Hardness Number Rock (VHNR), are indirect measures of rock drillability. These indices are recognized as providing practical characterization of rock properties used in the Norwegian University of Science and Technology (NTNU) time and cost prediction models available for hard rock tunneling and surface excavation. The tests form the foundation of various hard rock equipment capacity and performance prediction methods. In this paper, application of the tests for tunnel boring machine (TBM) and drill and blast (D&B) tunneling is investigated and the impact of the indices on excavation time and costs is presented.

Marine resistivity tomography for coastal engineering applications in Greece

The marine resistivity tomography method can be useful for coastal engineering applications through the use of immersion cables, laid on the water bottom, thus achieving a deeper and more detailed detection of the formations underneath. Careful positioning of the profiles related to the available geologic, geomorphological, bathymetric, and drilling data and to the requirements of engineers, can give thicknesses of loose material as well as the bedrock relief. The formations and their interfaces are clearly defined either by calibration with available drilling data or by high resistivity changes which indicate discontinuities with resistivity values related to permeability and saline water presence. Two case studies are under examination. The first concerns the preservation of an old iron bridge in Lavrion Port with reinforcement and new foundations. Here, the geophysical investigation detects the formation on which the bridge was founded, as well as the loose material above it. The second case study concerns geophysical investigation asked by a construction company for the marine excavation work needed in the new Mesta port. Here, the geophysical measurements with the detected formations give valuable information with respect to the volume of material, equipment, time and cost of excavation as well as where the foundations will be laid for new constructions.

The investigation of approximate cost and progress payment for forest road building in Lakes Region of Turkey

Forest roads are high-cost basic facilities allowing economic, ecological and social functions of forests to be fulfilled. Because the most essential work item affecting road construction cost is excavation works, amount of excavation and land classifications have to be most appropriately determined within bidding process. In regard to application, the amount of work given in approximate cost sheet required for bidding for forest road construction is determined by means of observational methods and the bidding is conducted within the scope of Public Procurement Law No:4734 before the project is made. After the documents including approximate cost, bidding and payment for 43 forest roads built in The Lakes Region of Turkey (Isparta Regional Directorate of Forestry) during the period (2003-2008) were obtained, the project started. The amount and cost of work determined in the bidding process for the roads involved in the research have been compared with those determined in the progress payment process. Within these comparisons, a consideration has been carried out by using tables, graphics and statistical methods. After the bidding files in the scope of Public Procurement Law in force were inspected, faulting components of the current application have been determined and solutions are suggested. It has been detected that the cost and amount of excavation determined in the bidding process differ from those determined in the payment process. It has been found out that it is not sufficient to determine amount of work given in bidding sheets related to road construction only by means of observation-based field reconnaissance. Projects providing better results as a result of using modern methods which can specify structure of land depth while conducting a road construction shall be designed. For this reason, geophysical methods can be benefited from. In order to conduct effectively biddings for forest road construction, amount of excavation and its distribution to land classifications shall be most appropriately determined.

Modeling parametric uncertainty in optimal open channel design using FORM-PGSL coupled approach

Optimal design of artificial open channels is essential for the planning and management of irrigation projects. In this paper a modified formulation is presented for the comprehensive design of open channels considering the seepage loss, evaporation loss and land acquisition cost along with the lining and excavation cost. The resulting formulation is solved using a recent meta-heuristic optimization technique namely probabilistic global search Lausanne (PGSL). The uncertainty associated with channel design parameter may lead to the failure of canals (channels). The parametric uncertainty in open channel design is modeled using first order reliability method (FORM). A bi-objective optimization model is presented in the study which minimizes the cost and minimizes the probability of overtopping considering a probabilistic cost function as the objective function. A new approach is proposed to solve the model in a meta-heuristic environment following PGSL as the solution method. Also a chance constrained optimization model which considers overtopping probability constraint and channel capacity constraint simultaneously along with the objective of minimization of cost is propounded and solved using PGSL. The solutions obtained using coupled FORM-PGSL approach is encouraging and the method can be used for optimal and reliable design of artificial open channels.

Proposed Reliability Techniques on Soil and Rock Excavations

Problem statement: Assessment of the ground mass excavation is normally done by the deterministic method. A quantitative indication of mass stability provides as an index term known "the Factor of Safety (F.S.)". There are uncertain to some degrees, such as only a single value of mass properties is used or variation in geologic conditions, computed values of F.S. are never absolutely precise. An alternative measurement of stability regarding use of index terms "Reliability (R) and probability of failure [p (f)]" is to cope with the uncertainty well. Concurrent processes of stability assessment are done using both the deterministic and reliability methods. Field data on the reliability approach assumed to be either normal function or lognormal function distribution. Conclusion/Recommendations: Three types of reliability model are proposed. Modeling types are based on the safety margin, the most likely value of F.S. and data simulation, respectively. These probabilistic values obtained from each model, are compared with the deterministic method. The risk on ground mass failures and environmental impacts due to excavation, be better defined and also achieved the optimized cost of construction excavation.

Heuristic algorithms for the multi-depot ring-star problem

In this paper, we consider the problem of designing urban optical networks. In particular, given a set of telephone exchanges, we must design a collection of ring-stars, where each ring-star is a cycle composed of a telephone exchange, some customers, some transition points used to save routing costs and customers not on the cycle connected to the cycle by a single edge. The ring topology is chosen in many fiber optic communication networks since it allows to prevent the loss of connection due to a single edge or even a single node failure. The objective is to minimize the total cost of the optical network which is mainly due to the excavation costs. We call this problem Multi-Depot Ring-Star Problem (MDRSP) and we formulate it as an optimization problem in Graph Theory. We present lower bounds and heuristic algorithms for the MDRSP. Computational results on randomly generated instances and real-life datasets are also presented.

The Oxnard advanced water purification facility: combining indirect potable reuse with reverse osmosis concentrate beneficial use to ensure a California community's water sustainability and provide coastal wetlands restoration

The City of Oxnard in California is implementing a strategic water resources program known as the Groundwater Recovery Enhancement and Treatment (GREAT) program, which includes an Advanced Water Purification Facility (AWPF) that will use a major portion of the secondary effluent from the City's existing Water Pollution Control Facility to produce high-quality treated water to be used for irrigation of edible food crops, landscape irrigation, injection into the groundwater basin to form a barrier to seawater intrusion, and other industrial uses. The AWPF, currently under design by CH2M HILL, will employ a multiple-barrier treatment train consisting of microfiltration, reverse osmosis, and ultravioletlightbased advanced oxidation processes to purify the secondary effluent to conform to California Department of Public Health Title 22 Recycled Water Criteria for groundwater recharge. The AWPF, which will have initial and build-out capacities of ca. 24,000 and ca 95,000 m(3)/day, respectively, was limited to a 1.8-hectare site, with 0.4 hectares dedicated to a Visitor's Center and administration building. Further, the depth below grade and height of the AWPF's structures were constrained because of the high groundwater table at the site, the high cost of excavation and dewatering, and local codes. To accommodate these various restrictions, an innovative design approach has been developed. This paper summarizes the design constraints and innovative solutions for the design of the AWPF.