A heuristic approach to stochastic cutoff grade optimization for open pit mining complexes with multiple processing streams

This paper describes a new, miniature, instrumented flat dilatometer (mIDMT) designed to assess variations in nearly continuous compressive stress–strain behaviour with depth in shallow cohesive sediments. The instrument was tested both in situ in the Bay of Fundy, Nova Scotia, Canada, and in cored samples from Willapa Bay, Washington, USA. Comparisons between probe and laboratory uniaxial assessments for other elastic materials—gelatine and foam rubber specifically—show strong agreement over the range of strains induced in the experiments. Observed values of Young’s modulus (E) for the gelatine and ethylene-vinyl acetate foam ranged from 6–343 kPa. Sediment stress–strain curves were distinctly linear for the overconsolidated fine-grained sediments of the Minas Basin, and values of E were found to increase with depth from near zero to 500–1,300 kPa at 20 cm depth. At the Willapa site, the sandy tidal flat sediments also behave elastically but E tended to increase more strongly with depth than for sediments from the Minas Basin. Young’s modulus was inversely correlated to porosity at all sites tested, and linearly related to shear strength in the Minas Basin. The newly designed instrument has much finer resolution than for other, similar methods of determining E in situ, and it provides data at a resolution sufficient to assess small-scale processes such as gas bubble growth and infaunal locomotion, for which elastic constants are needed for modelling and prediction.

A new instrument for high-resolution in situ assessment of Young’s modulus in shallow cohesive sediments

The evaluation of rate effects on the flat dilatometer test (DMT) can best be developed with some knowledge of the excess pore pressures generated during penetration, dissipation, and subsequent me...

Effects of test procedure on flat dilatometer test (DMT) results in intermediate soils

https://file.scirp.org/pdf/ENG20121100015_39355361.pdf

Evaluation of the Ultimate Capacity of Friction Piles

/pdf/strength-hydraulic-and-microstructural-characteristics-of-4k2uqtpems.pdf

Strength, Hydraulic, and Microstructural Characteristics of Expansive Soils Incorporating Marble Dust and Rice Husk Ash

The Marchetti flat dilatometer is a simple to operate in-situ testing device that was designed for use in clays, silts, and sands. A new dilatometer has been developed for use in a greater variety of soil types, in particular glacial tills. This probe is more robust than the Marchetti dilatometer because it uses a rigid piston instead of a flexible membrane to load the soil. The new dilatometer is also a research dilatometer incorporating a displacement transducer and pressure transducer. This allows an applied pressure displacement curve to be produced. Tests have been carried out at several sites to compare results from the two dilatometers, check the robustness of the new dilatometer, and produce data to establish new correlations.

A flat dilatometer to operate in glacial tills

Expansive soils occur at some places of Pakistan. This paper describes the problems related to expansive soils discovered at Gomal University, Dera Ismail Khan and Shah Abdul Latif University, Khairpur. On the basis of field and laboratory tests for these two sites, certain corrective measures both for the design and construction of foundations/floors have been suggested.

Expansive soils in pakistan - case histories

The precise prediction of maximum load carrying capacity of bored piles is a complex problem because it is a function of a number of factors. These factors include method of boring, method of concreting, quality of concrete, expertise of the construction staff, the ground conditions etc. besides the pile geometry. The performance of pile load tests is, therefore, of paramount importance to establish the most economical design of piles especially where bored cast-in-situ piles are to be provided to support a structure. This paper describes the experience gained from four pile load tests at a site in the North West Frontier Province of Pakistan where a new cement plant is going to be installed. Geotechnical investigations at the site were carried out to a maximum depth of 60 m. The subsoils at the site are predominantly hard clays within the investigated depth with thin layers of gravels / boulders below 40 m depth. Perched water was encountered at various horizons. Four piles of diameter varying from 660 mm to 760 mm and length ranging between 20 m and 47.5 m were subjected to axial loads. The load test data were analyzed using various state of the art techniques including intercept of two tangents, point of change of slope, 6 mm net settlement [1], 90 percent and 80 percent Hansen [7], limit value Davisson [2], and Chin [3]. Based on a comparison of pile capacities from these methods with the theoretical values, recommendations are made on the approach to estimate the pile capacity in hard clays. Using the pile load test results, back calculations were also carried out to estimate the appropriate values of pile design parameters such as undrained cohesion and adhesion factor.

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Shaft Friction of Bored Piles in Hard Clay

A new pressuremeter has been developed at the University of Engineering and Technology, Lahore-Pakistan with some modifications / improvements in the Newcastle full displacement pressuremeter (NFDPM), developed by Akbar in 2001. The device is now called Akbar Pressuremeter (APMT). Tests in soils can be performed using the APMT by full displacement as well as pre-bored techniques. This paper describes the results of characterization of an artificially prepared cohesive soil bed comprising low plastic lean clay (CL) to sandy silty clay (CL-ML) using the APMT. This testing was carried out by pre-bored technique. For this purpose initially borehole produced up to the desired test level using auger and then device was inserted into the borehole to conduct the test. The pressuremeter (PMT) testing was carried out at two locations at 1.0 m intervals to 5.0 m depth. Undisturbed soil samples (UDS) were taken from nearby locations at the level of each APMT test using Shelby tubes. These samples were subjected to various conventional laboratory tests to correlate with the APMT test results. The standard penetration tests (SPTs) were also carried out in the near vicinity at the level of each APMT in order to correlate PMT data with the SPT data. Undrained shear strength of each UDS was determined by performing unconfined compression test. The PMT parameters viz. soil strength and stiffness, determined from the corrected pressure-cavity strain curves of each APMT test and those from laboratory methods, have been compared and correlations have been drawn. The findings of this study are that the APMT can be used to characterize a cohesive soil bed.

/pdf/characterization-of-an-artificially-prepared-cohesive-soil-5ebu6y8ur8.pdf

Characterization of an Artificially Prepared Cohesive Soil Bed

Raising of the Mangla Dam in Pakistan submerged about 15,780 acres of land, resulting in the relocation of 8020 inhabitants to a newly developed town named New City. The new site, consisting of 1300 acres, is in the sub-tropical zone and comprises badland topography. The parent soils (Siwalik clay) pose infrastructure serviceability issues, causing immense loss to property. The study aims to improve the properties of Siwalik clay (base soil) using industrial wastes like marble and glass powders (5 to 20%) and polypropylene fibers (0.25 to 1.25%) as modifiers. Laboratory tests including grain size distribution, Atterberg limits, standard Proctor compaction, unconfined compression, indirect tensile strength, swell potential, and California bearing ratio were conducted on the control and modified clay samples. The results showed that unconfined compressive strength (UCS) and swelling strains (SS) were increased by 43% and 8% at 1.57 kPa pressure with 15% replacement of marble powder. However, the addition of the 20% glass powder and 0.5% polypropylene fibers not only improved UCS by 110% and 39%, but also reduced SS by 27% and 86%, respectively. The capital construction cost of 1 km long road with modified subgrade using 15% glass powder was reduced by 16% whereas it increased for marble powder and polypropylene fibers by 22% and 17%, respectively. All modifiers had very low hazard to adjoining aqueous environment. Conclusively, glass powder and polypropylene fibers can be used as environmentally-friendly soil improvement modifiers, leading towards sustainable solutions of the serviceability problems.

/pdf/suitability-assessment-of-marble-glass-powders-and-poly-3hste1t4.pdf

A. Akbar

Papers

A flat dilatometer to operate in glacial tills

Expansive soils in pakistan - case histories

Shaft Friction of Bored Piles in Hard Clay

Characterization of an Artificially Prepared Cohesive Soil Bed

Suitability Assessment of Marble, Glass Powders and Poly-Propylene Fibers for Improvement of Siwalik Clay