Statnamic load test

The Statnamic load test is a type of test for assessing the load-carrying capacity of deep foundations which is faster and less expensive than the static load test. The Statnamic test was conceived in 1985, with the first prototype tests carried out in 1988 through collaboration between Berminghammer Foundation Equipment of Canada and TNO Building Research of the Netherlands (Middendorp et al., 1992 & Middendorp, 2000). Guidance on rapid load pile testing can be found in: Methods for Axial Compressive Force Pulse (Rapid) Testing of Deep Foundations. Sanken D7383 - 08 Standard Test.

How it works

Statnamic testing works by accelerating a mass upward that in turn imparts a load onto the foundation pile below the Statnamic device. The load is applied and removed smoothly resulting in load application of 100 to 200 milliseconds. This is 30 to 40 times the duration of dynamic pile load testing. As the duration of the loading is relatively long, piles less than 40 m in length remain in compression throughout, resulting in negligible stress wave effects and potentially simpler analysis. For foundation design it is necessary to derive the equivalent static load-settlement curve from the Statnamic data. The simplest form of Statnamic analysis used to obtain equivalent static pile response is known as the unloading point method (UPM). The UPM analysis method was conceived to be simple and based on measured results alone (Middendorp et al., 1992).

The Statnamic test applies a force to the pile head over a typical duration of 120 milliseconds by the controlled venting of high-pressure gas. The gas is the product of the combustion of a fast-burning fuel within a piston (fuel chamber) (Figure 1). At the top of the piston are vent holes that are sealed by the load hanger retaining the reaction mass. At some point the pressure within the piston is of such a magnitude to force the load hanger arrangement upward at accelerations in order of 196m/s2 (20g). This process applies a load downwards on the test pile.

During the loading sequence the load applied to the test pile is monitored by a calibrated load cell incorporated in the base of the combustion piston. Pile settlement is measured using a remote laser reference source that falls on a photovoltaic cell incorporated in the piston. The laser reference source should be placed at least 15 m from the test pile to avoid the influence of test-induced ground surface wave disturbance (Brown & Hyde, 2006). Data capture is undertaken using a data acquisition system connected to a laptop computer. It is recommended to allow accurate data processing that sampling should be undertaken at frequencies above 1 kHz.

Typical equipment

The most common form of Statnamic rigs typically have testing capacities of 3 to 4 MN. These devices are self-contained and may be transported using a single articulated lorry. Whilst on site they require the use of a mobile crane with a typical capacity of 70 tonnes, with mobilisation in less than 2 hours. In addition to these typical capacities, devices have been produced which can apply maximum loads ranging from 0.3 to 60 MN. To achieve greater loads the major components of the device, including the piston, silencer-weight hanger and reaction mass, must be scaled up in size.

The Statnamic weight packs usually consist of steel or concrete rings placed over the Statnamic silencer. As the device does not rely on gravity to apply loads as in static or drop weight testing it can be used vertically, horizontally and inclined to test raked piles. The ability to test horizontally has led to the method being used for lateral load testing of piles and simulation of ship impacts on mooring bodies (Middendorp, 2000). In order to improve the flexibility of the device and minimise transportation costs for offshore works, a device has also been tested that can apply up to 14 MN using water as a reaction mass. This is achieved in over-water pile tests by connecting the Statnamic device to a vessel full of water below the water body's surface (Middendorp, 2000), thus removing the need for heavy reaction weights.

The only significant difference between the smaller and larger testing devices is the method of catching the reaction mass. The catching method for larger tests uses gravel. This is achieved by placing the Statnamic device on the test pile and lowering the reaction mass onto its hanger. A large containing container is then placed around the assembly and filled with gravel. As the Statnamic weights move upwards the gravel moves to fill the void left and support the weights once movement has ceased. Due to the time required to place and remove the gravel after testing this method is reserved for tests above 16 MN. Smaller rigs utilise a hydraulic catching mechanism that allows the mass to be caught within the frame of the device. This allows up to ten individual piles to be tested in a day or multiple cycles on a single pile at 15-minute intervals. Further description of the hydraulic catching mechanism is given by Middendorp (2000). The most recent development is the mounting of a 1 MN Statnamic device on a 360° tracked excavator which allows rapid deployment (1 hour) and increased production.

See also

References

External links

Borehole

A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water, other liquids (such as petroleum) or gases (such as natural gas), as part of a geotechnical investigation, environmental site assessment, mineral exploration, temperature measurement, as a pilot hole for installing piers or underground utilities, for geothermal installations, or for underground storage of unwanted substances, e.g. in carbon capture and storage.

Clay

Clay is a finely-grained natural rock or soil material that combines one or more clay minerals with possible traces of quartz (SiO2), metal oxides (Al2O3 , MgO etc.) and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to particle size and geometry as well as water content, and become hard, brittle and non–plastic upon drying or firing. Depending on the soil's content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red.

Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in particle size and other physical properties. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm (clays being finer than silts), sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay particles as being smaller than 2 μm and silt particles as being larger.

Mixtures of sand, silt and less than 40% clay are called loam. Loam makes good soil and is used as a building material.

Exploration geophysics

Exploration geophysics is an applied branch of geophysics and economic geology, which uses physical methods, such as seismic, gravitational, magnetic, electrical and electromagnetic at the surface of the Earth to measure the physical properties of the subsurface, along with the anomalies in those properties. It is most often used to detect or infer the presence and position of economically useful geological deposits, such as ore minerals; fossil fuels and other hydrocarbons; geothermal reservoirs; and groundwater reservoirs.

Exploration geophysics can be used to directly detect the target style of mineralization, via measuring its physical properties directly. For example, one may measure the density contrasts between the dense iron ore and the lighter silicate host rock, or one may measure the electrical conductivity contrast between conductive sulfide minerals and the resistive silicate host rock.

Gravel

Gravel is a loose aggregation of rock fragments. Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments. In the Udden-Wentworth scale gravel is categorized into granular gravel (2 to 4 mm or 0.079 to 0.157 in) and pebble gravel (4 to 64 mm or 0.2 to 2.5 in). ISO 14688 grades gravels as fine, medium, and coarse with ranges 2 mm to 6.3 mm to 20 mm to 63 mm. One cubic metre of gravel typically weighs about 1,800 kg (or a cubic yard weighs about 3,000 pounds).

Gravel is an important commercial product, with a number of applications. Many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or asphalt; Russia alone has over 400,000 km (250,000 mi) of gravel roads. Both sand and small gravel are also important for the manufacture of concrete.

Mass wasting

Mass wasting, also known as slope movement or mass movement, is the geomorphic process by which soil, sand, regolith, and rock move downslope typically as a solid, continuous or discontinuous mass, largely under the force of gravity, frequently with characteristics of a flow as in debris flows and mudflows. Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on Earth, Mars, Venus, and Jupiter's moon Io.

When the gravitational force acting on a slope exceeds its resisting force, slope failure (mass wasting) occurs. The slope material's strength and cohesion and the amount of internal friction within the material help maintain the slope's stability and are known collectively as the slope's shear strength. The steepest angle that a cohesionless slope can maintain without losing its stability is known as its angle of repose. When a slope made of loose material possesses this angle, its shear strength counterbalances the force of gravity acting upon it.

Mass wasting may occur at a very slow rate, particularly in areas that are very dry or those areas that receive sufficient rainfall such that vegetation has stabilized the surface. It may also occur at very high speed, such as in rockslides or landslides, with disastrous consequences, both immediate and delayed, e.g., resulting from the formation of landslide dams. Factors that change the potential of mass wasting include: change in slope angle, weakening of material by weathering, increased water content; changes in vegetation cover, and overloading.

Volcano flanks can become over-steep resulting in instability and mass wasting. This is now a recognised part of the growth of all active volcanoes. It is seen on submarine as well as surface volcanoes: Loihi in the Hawaiian volcanic chain and Kick 'em Jenny in the Caribbean volcanic arc are two submarine volcanoes that are known to undergo mass wasting. The failure of the northern flank of Mount St Helens in 1980 showed how rapidly volcanic flanks can deform and fail.

Natchez silt loam

In 1988, the Professional Soil Classifiers Association of Mississippi selected Natchez silt loam soil to represent the soil resources of the State. These soils exist on 171,559 acres (0.56% of state) of landscape in Mississippi.

Permeability (earth sciences)

Permeability in fluid mechanics and the earth sciences (commonly symbolized as k) is a measure of the ability of a porous material (often, a rock or an unconsolidated material) to allow fluids to pass through it.

The permeability of a medium is related to the porosity, but also to the shapes of the pores in the medium and their level of connectedness.

Response spectrum

A response spectrum is a plot of the peak or steady-state response (displacement, velocity or acceleration) of a series of oscillators of varying natural frequency, that are forced into motion by the same base vibration or shock. The resulting plot can then be used to pick off the response of any linear system, given its natural frequency of oscillation. One such use is in assessing the peak response of buildings to earthquakes. The science of strong ground motion may use some values from the ground response spectrum (calculated from recordings of surface ground motion from seismographs) for correlation with seismic damage.

If the input used in calculating a response spectrum is steady-state periodic, then the steady-state result is recorded. Damping must be present, or else the response will be infinite. For transient input (such as seismic ground motion), the peak response is reported. Some level of damping is generally assumed, but a value will be obtained even with no damping.

Response spectra can also be used in assessing the response of linear systems with multiple modes of oscillation (multi-degree of freedom systems), although they are only accurate for low levels of damping. Modal analysis is performed to identify the modes, and the response in that mode can be picked from the response spectrum. These peak responses are then combined to estimate a total response. A typical combination method is the square root of the sum of the squares (SRSS) if the modal frequencies are not close. The result is typically different from that which would be calculated directly from an input, since phase information is lost in the process of generating the response spectrum.

The main limitation of response spectra is that they are only universally applicable for linear systems. Response spectra can be generated for non-linear systems, but are only applicable to systems with the same non-linearity, although attempts have been made to develop non-linear seismic design spectra with wider structural application. The results of this cannot be directly combined for multi-mode response.

Sand

Sand is a granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass.The composition of sand varies, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the form of quartz. The second most common type of sand is calcium carbonate, for example, aragonite, which has mostly been created, over the past half billion years, by various forms of life, like coral and shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean.

Sand is a non-renewable resource over human timescales, and sand suitable for making concrete is in high demand. Desert sand, although plentiful, is not suitable for concrete. 50 billion tons of beach sand and fossil sand is used each year for construction.

Seismic hazard

A seismic hazard is the probability that an earthquake will occur in a given geographic area, within a given window of time, and with ground motion intensity exceeding a given threshold. With a hazard thus estimated, risk can be assessed and included in such areas as building codes for standard buildings, designing larger buildings and infrastructure projects, land use planning and determining insurance rates. The seismic hazard studies also may generate two standard measures of anticipated ground motion, both confusingly abbreviated MCE; the simpler probabilistic Maximum Considered Earthquake (or Event ), used in standard building codes, and the more detailed and deterministic Maximum Credible Earthquake incorporated in the design of larger buildings and civil infrastructure like dams or bridges. It is important to clarify which MCE is being discussed.

Calculations for determining seismic hazard were first formulated by C. Allin Cornell in 1968 and, depending on their level of importance and use, can be quite complex. The regional geology and seismology setting is first examined for sources and patterns of earthquake occurrence, both in depth and at the surface from seismometer records; secondly, the impacts from these sources are assessed relative to local geologic rock and soil types, slope angle and groundwater conditions. Zones of similar potential earthquake shaking are thus determined and drawn on maps. The well known San Andreas Fault is illustrated as a long narrow elliptical zone of greater potential motion, like many areas along continental margins associated with the Pacific ring of fire. Zones of higher seismicity in the continental interior may be the site for intraplate earthquakes) and tend to be drawn as broad areas, based on historic records, like the 1812 New Madrid earthquake, since specific causative faults are generally not identified as earthquake sources.

Each zone is given properties associated with source potential: how many earthquakes per year, the maximum size of earthquakes (maximum magnitude), etc. Finally, the calculations require formulae that give the required hazard indicators for a given earthquake size and distance. For example, some districts prefer to use peak acceleration, others use peak velocity, and more sophisticated uses require response spectral ordinates.

The computer program then integrates over all the zones and produces probability curves for the key ground motion parameter. The final result gives a 'chance' of exceeding a given value over a specified amount of time. Standard building codes for homeowners might be concerned with a 1 in 500 years chance, while nuclear plants look at the 10,000 year time frame. A longer-term seismic history can be obtained through paleoseismology. The results may be in the form of a ground response spectrum for use in seismic analysis.

More elaborate variations on the theme also look at the soil conditions. Higher ground motions are likely to be experienced on a soft swamp compared to a hard rock site. The standard seismic hazard calculations become adjusted upwards when postulating characteristic earthquakes. Areas with high ground motion due to soil conditions are also often subject to soil failure due to liquefaction. Soil failure can also occur due to earthquake-induced landslides in steep terrain. Large area landsliding can also occur on rather gentle slopes as was seen in the Good Friday earthquake in Anchorage, Alaska, March 28, 1964.

Seismoelectrical method

The seismoelectrical method (which is different from the electroseismic physical principle) is based on the generation of electromagnetic fields in soils and rocks by seismic waves. This technique is still under development and in the future it may have applications like detecting and characterizing fluids in the underground by their electrical properties, among others, usually related to fluids (porosity, transmissivity, physical properties).

Sieve analysis

A sieve analysis (or gradation test) is a practice or procedure used (commonly used in civil engineering) to assess the particle size distribution (also called gradation) of a granular material by allowing the material to pass through a series of sieves of progressively smaller mesh size and weighing the amount of material that is stopped by each sieve as a fraction of the whole mass.

The size distribution is often of critical importance to the way the material performs in use. A sieve analysis can be performed on any type of non-organic or organic granular materials including sands, crushed rock, clays, granite, feldspars, coal, soil, a wide range of manufactured powders, grain and seeds, down to a minimum size depending on the exact method. Being such a simple technique of particle sizing, it is probably the most common.

Silt

Silt is granular material of a size between sand and clay, whose mineral origin is quartz and feldspar. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water (also known as a suspended load) and soil in a body of water such as a river. It may also exist as soil deposited at the bottom of a water body, like mudflows from landslides. Silt has a moderate specific area with a typically non-sticky, plastic feel. Silt usually has a floury feel when dry, and a slippery feel when wet. Silt can be visually observed with a hand lens, exhibiting a sparkly appearance. It also can be felt by the tongue as granular when placed on the front teeth (even when mixed with clay particles).

Specific storage

In the field of hydrogeology, storage properties are physical properties that characterize the capacity of an aquifer to release groundwater. These properties are storativity (S), specific storage (Ss) and specific yield (Sy).

They are often determined using some combination of field tests (e.g., aquifer tests) and laboratory tests on aquifer material samples. Recently, these properties have been also determined using remote sensing data derived from Interferometric synthetic-aperture radar.

Static load testing

Static load testing is an in situ type of load testing used in geotechnical investigation to determine the bearing capacity of deep foundations prior to the construction of a building. It differs from the statnamic load test and dynamic load testing in that the pressure applied to the pile is slower.

Sultan Abdul Halim Muadzam Shah Bridge

The Sultan Abdul Halim Muadzam Shah Bridge or Penang Second Bridge (Malay: Jambatan Sultan Abdul Halim Muadzam Shah or Jambatan Kedua Pulau Pinang; Chinese: 苏丹阿都哈林跨海大桥; Tamil: சுல்தான் அப்துல் ஹாலிம் முவாட்சாம் ஷா பாலம் or பினாங்கு இரண்டாவது பாலம்) is a dual carriageway toll bridge in Penang, Malaysia. It connects Bandar Cassia (Batu Kawan) in Seberang Perai on mainland Peninsular Malaysia with Batu Maung on Penang Island. It is the second bridge to link the island to the mainland after the first Penang Bridge.

The total length of the bridge is 24 km (15 mi) with length over water at 16.9 km (10.5 mi), making it the longest bridge in Malaysia and the longest in Southeast Asia. China Harbour Engineering Co Ltd (CHEC), a main contractor for the second bridge was expected to start work on the second Penang bridge in November 2007 and complete the project in 2011, but the completion date was then postponed to May 2012, and later to February 2014.Construction started in November 2008. To reduce the cost of construction, its design was then modified to resemble the first cable stayed Penang Bridge. The bridge has been built with a large loan from the People's Republic of China to continue and maintain the economic relationship between China and Malaysia. The bridge was officially opened on 1 March 2014 at 20:30 MST and was named after the fourteenth Yang di-Pertuan Agong, the late Tuanku Abdul Halim Muadzam Shah of Kedah and was assigned with the route number E28.

Thixotropy

Thixotropy is a time-dependent shear thinning property. Certain gels or fluids that are thick or viscous under static conditions will flow (become thin, less viscous) over time when shaken, agitated, sheared or otherwise stressed (time dependent viscosity). They then take a fixed time to return to a more viscous state.

Some non-Newtonian pseudoplastic fluids show a time-dependent change in viscosity; the longer the fluid undergoes shear stress, the lower its viscosity. A thixotropic fluid is a fluid which takes a finite time to attain equilibrium viscosity when introduced to a steep change in shear rate. Some thixotropic fluids return to a gel state almost instantly, such as ketchup, and are called pseudoplastic fluids. Others such as yogurt take much longer and can become nearly solid. Many gels and colloids are thixotropic materials, exhibiting a stable form at rest but becoming fluid when agitated. Thixotropy arises because particles or structured solutes require time to organize. An excellent overview of thixotropy has been provided by Mewis and Wagner.Some fluids are anti-thixotropic: constant shear stress for a time causes an increase in viscosity or even solidification. Fluids which exhibit this property are sometimes called rheopectic. Anti-thixotropic fluids are less well documented than thixotropic fluids.

Trench

A trench is a type of excavation or depression in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared with its length (as opposed to a simple hole).In geology, trenches are created as a result of erosion by rivers or by geological movement of tectonic plates. In the civil engineering field, trenches are often created to install underground infrastructure or utilities (such as gas mains, water mains or telephone lines), or later to access these installations. Trenches have also often been dug for military defensive purposes. In archaeology, the "trench method" is used for searching and excavating ancient ruins or to dig into strata of sedimented material.

Void ratio

The void ratio of a mixture is the ratio of the volume of voids to volume of solids.

It is a dimensionless quantity in materials science, and is closely related to porosity as follows:

and

where is void ratio, is porosity, VV is the volume of void-space (such as fluids), VS is the volume of solids, and VT is the total or bulk volume. This figure is relevant in composites, in mining (particular with regard to the properties of tailings), and in soil science. In geotechnical engineering, it is considered as one of the state variables of soils and represented by the symbol e.

Note that in geotechnical engineering, the symbol usually represents the angle of shearing resistance, a shear strength (soil) parameter. Because of this, the equation is usually rewritten using for porosity:

and

where is void ratio, is porosity, VV is the volume of void-space (air and water), VS is the volume of solids, and VT is the total or bulk volume.

Soil
Foundations
Retaining walls
Stability
Earthquakes
Geosynthetics
Numerical analysis

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