Showing papers on "Settlement (structural) published in 1991"

Settlement behaviour of ascidian larvae: preliminary evidence for inhibition by sponge allelochemicals

Abstract: Recruitment in many marine invertebrates is inherently variable; the behaviour of larvae at settlement may be an important contributor to this variation. Yet there are few in situ observations of settlement behaviour of marine invertebrate larvae. Direct observations in the field showed that 63 % (n = 89) in larvae of the colonial ascidian PodoclaveUa moluccensisSluiter settled on their first contact with the substratum, whde a small percentage made 10 or more contacts prior to settlement. Two species of subtidal sponge, Mycale sp. and Crella incrustans, were consistently avoided by these settlmg larvae. Mycale sp, was often contacted repeatedly, but invariably rejected. In contrast, even contacts with C. incrustans were rare, relative to the space that t h s sponge occupied. We investigated the role of sponge allelochemicals, at natural concentrations, In inhibiting settlement of these larvae. Settlement of larvae onto substrata impregnated with an ether-soluble extract of Mycale sp. was significantly inhibited, relative to controls. Several fractions of this extract were equally inhibitory to setthng larvae. Butanol and ether extracts of C. incrustans were also inhibitory and the repellent activity was in the more polar lipophilic fractions. The least polar fraction was attractive to larvae. Extracts appeared to be non-toxic to the larvae and we failed to detect any antibacterial activity. We conclude that settlement of these ascidian larvae may be inhibited by natural products released from or at the surface of these sponges.

Patterns of settlement and growth of juvenile flounder Rhombosolea tapirina determined from otolith microstructure

Abstract: Otolith microstructure was used to examine settlement and growth of juvenile Rhombosolea t a p m a Gunther from a site within Swan Bay, Victoria, Australia. A distinct transition zone on sagittae coincides with settlement from the pelagic larval phase to the benthic juvenile habitat. The daily settlement pattern was reconstructed using otolith increments from fish collected during and at the end of the settlement season. Settlement was continuous from July to October. However, most individuals had apparently immigrated from other settlement areas or were inaccessible to sampling for a brief period after settlement The settlement pattern persisted over time, however, peaks were no longer evident at the end of the settlement season. The population growth rate of juvenile flounder was found to be approximately linear over the size range sampled, averaging 0.29 mm d l A significant linear relationship between standard length and otolith radius allowed back-calculation of individual growth trajectories for a 'winter' and a 'spring' cohort Significant differences were found in growth trajectories for each cohort, growth rate over the first 20 d post settlement for the winter cohort averaged approximately 0.17 mm d compared to 0 23 mm d for the spring cohort The relationship between daily growth and air temperature was compared using cross correlation. Cross correlation functions showed a significant positive correlation at lags of 2 to 5 d for the winter cohort and a significant negative correlation at a lag of 1 d for the spring cohort This suggests that early in the settlement season, temperature had a positive influence on metabolism, which in turn affected somatic and otohth growth rates. However, temperature apparently reached a critical level later m the season, which resulted in high temperature having a deleterious effect on metabolism, leading to a negative correlation between temperature and growth.

Incorporating Variation in Occupation Span into Settlement-Pattern Analysis

Abstract: Settlement patterns recovered by archaeologists differ fundamentally from synchronic settlement patterns analyzed by geographers since they are a static record of occupations that may often have had differing periods of use in the past. Many maps of the “settlement pattern” of prehistoric phases show more occupations than were ever simultaneously occupied. After discussing some of the problems this can cause, I describe a way of characterizing past settlement dynamics and a method for estimating (1) the mean number of likely simultaneous occupations for a region and (2) phase-to-phase differences in mean occupation span. The method is illustrated by the analysis of settlement data from the Ixtapalapa region in the Basin of Mexico.

Settlement of Footings on Sands—Accuracy and Reliability

Abstract: Twelve methods of estimating settlements of footings on sand were evaluated by comparing calculated settlements with measured settlements. Each of the methods was evaluated in terms of (1) accuracy (how does the average calculated settlement compare to the average measured settlement?), (2) reliability ( in what percentage of cases does the calculated settlement equal or exceed the measured settlement?), and (3) ease of use (how long is required to apply the method?). The methods suggested by D'Appolonia and D'Appolonia (1970) and by Terzaghi and Peck (1967) were found to afford reasonable combinations of accuracy and reliability, with fairly low amounts of time required for the analyses.

Dolní Věstonice II western slope.

Abstract: A complex publication of the 1987 excavation of a part of a large hunter s settlement, including a male burial in one of the dwellings. Země vydani : Belgie

Wall panels and methods of construction thereof

Abstract: A wall panel comprises at least two standards, a plurality of logs which are supported by and movable relative to the standards and a plurality of preferably self-compensating jacks which support a load, for example a roof or an upper storey, above the upper edge of the uppermost log, the self-compensating jacks supporting the load with preferably a constant force irrespective of vertical movement between the upper edge of the uppermost log and the load caused by, for example, settlement or shrinkage.

Pile group settlement: A probabilistic approach

Abstract: The uncertain settlement response of pile groups is determined using a ‘hybrid’ formulation and a first-order perturbation technique. The spatially varying soil modulus, which gives rise to the uncertainties in the pile group settlement, is modeled as a homogeneous random field. The random field is assumed to be one-dimensional since the ‘hybrid’ formulation does not account for horizontal variation in the soil properties. Using the proposed method, the coefficient of variation of the pile group settlement is computed. The single-pile solutions obtained compare favorably with the solutions from a conventional stochastic finite element analysis. Pile groups of sizes ranging from two to twenty-five piles are studied. It is observed that the coefficient of variation is not significantly affected by the pile spacing as well as the group size. By defining an appropriate performance function, the reliability index of a pile group system is also found to be approximately the same as that of a single-pile system. These observations suggest that the solutions for a single pile may be used to estimate the uncertainties in the settlement response of pile groups.

Waste water treatment plant

Abstract: Waste water treatment plant of the type in which liquid and solid components of waste water are first separated by settlement, biomass in the waste water is then subjected to digestion by microorganisms supported on rotary contactors (29, 30) which periodically expose the biomass to air, and finally the waste water undergoes a second settlement to separate remaining solids. The plant comprises a plurality of rotary contactor units (29, 30), each accommodated in a biozone tank (22, 24, 26) arranged in a row above respective primary settlement tanks (12, 14, 16). The axes of rotation of the units are transverse to the row of tanks, and each unit has its own individually controllable drive. A sludge storage tank is provided to receive settled sludge from the primary settlement tanks (12, 14, 16), the tank being divided into compartments (38, 40, 42), one per primary settlement tank. Pumps (44) are provided to transfer sludge from the primary settlement tanks (12, 14, 16) to the storage tank. The floors of the settlement tanks and sludge tanks are benched to localise the sludge for easy removal.

Wall panels, methods of construction thereof and buildings constructed therefrom

Abstract: A wall panel (10) comprises at least two standards (16,26), a plurality of logs (14) which are supported by and movable relative to the standards and a plurality of preferably self-compensating jacks (18) which support a load, for example a roof or an upper storey, above the upper edge of the uppermost log (14), the self-compensating jacks (18) supporting the load with preferably a constant force irrespective of vertical movement between the upper edge of the uppermost log (14) and the load caused by, for example, settlement or shrinkage.

Middle and Late Woodland Settlement Systems in the Interior Fall Zone of the Potomac Valley: Not a Live Oyster In Sight

Abstract: Recent excavations at two sites, Karell and Taft, in Fairfax County, Virginia yielded significant information on Middle and Late Woodland ceramics. These in junction with other Native American sites in the Fairfax County inventory have yielded many valuable insights into settlement patterns in interior (non-riverine) and upland environments.

Device for Control of Building Settlement and for Seismic Protection

Abstract: The device allows controlled transfer of the building loads to the foundation piles, such that the building neither settles nor emerges with respect to the surrounding ground, in areas where the subsoil is highly compressible, as is that of Mexico City. Additionally, the device dissipates energy when the building experiences rocking motion under the action of earthquake forces. The device is fixed to the head of each of the foundation piles, which pass freely through the building base slab. Also, the device is fixed to the base slab, such that it provides, by means of deformable elements that undergo a rolling-bending motion, a variable length connection between foundation piles and building.

Inclination-correcting method of inclined ancient tower

Abstract: This invention discloses a method for correcting inclined antient tower that is built on soft foundation. It features as follows: at the side of twoer where settlement is less a number of vertical wells are arranged at the edge of tower footing and a number of equidistant oblique wells which has a distance from vertical well are set up; the bottoms of vertical and oblique wells are connected to each other; and the earth under the tower footing at the bottom of vertical well is flushed into silt by pressurized water and air, and the silt is delivered to ground through oblique well, during which the amount of settlement at the side of tower where original settlement is less controlled. Thus, the inclination of antient tower is corrected.

Model Pile-Settlement Behavior in Frozen Sand

Abstract: Small cyclic loads, superimposed on a static load, will significantly increase settlement rates of friction piles embedded in frozen ground. An experimental study involving model steel piles with controlled surface geometry (lug size, shape, and spacing) provides information on displacement mechanisms operating at the pile/frozen-sand interface. Settlement rates due to static and incremental static loads are analyzed and compared to rate increases resulting from superimposed cyclic loads. Variables controlled during these tests include cyclic load amplitude, load application frequency, static load magnitudes, pile surface roughness, sand density, ice fraction, and sand particle size. Typically, a small static load increase of magnitude \IX\N produces a displacement rate increase corresponding to a cyclic load with amplitude of 1.4\IX\N. Measured creep rates are independent of frequency of 0.1–10 Hz. Larger lugs (more than twice the maximum particle size) densify and partially crush sand particles at their leading edge. The onset of increasing pile displacement rates (tertiary creep or failure) is shown to be a function of lug height and spacing.