Collapse potential of a compacted weathered serpentinite from Skiros Island, Greece

Grifiza

2016

E3S Web Conf.

Abstract. The mechanical behaviour of fine-grained soil materials to be used as impermeable cores for earth dams has been extensively studied by numerous researchers. The required properties of these materials have also been very well described by standards and specifications. Yet, more than often it is required to assess their swelling/collapse potential, especially at various vertical stresses, as a means to estimate their volume changes upon inundation which is going to be caused by filling the dam reservoir. In the paper, experimental results of five different soils are presented. The soils tested ranged from non-plastic silty sands with clay to medium plasticity clayey silts that were compacted in conditions dry, at and wet of optimum moisture content as derived from standard compaction energy Proctor tests, then subjected to one-dimensional loading conditions and then inundated. The vertical stress was up to 7.6 MPa. The experimental results are categorized according to initial moisture content relative to Proctor optimum and indicate expected magnitudes of strains due to inundation for various grain-size distributions and plasticities.

Section: Experimental Methodssupporting

confidence: 53%

Section: Swelling/collapse Strains Due To Inundationsupporting

confidence: 48%

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Swelling and collapse of compacted soils to be used as earth dam cores

Grifiza

2016

E3S Web Conf.

“…The shoulders of this dam are constructed of a compacted weathered serpentinite found locally in abundance (w L =27%, I p =8, G s =2.61, w opt =11%, γ d,max =19.3 kN/m 3 ). The properties of this material have been thoroughly investigated [1,2] and actual samples may be seen in Fig. 1b and c. Compacted samples of the material were prepared in the laboratory at the required dry unit weight (98% of the maximum dry unit weight obtained using the Proctor compaction test with standard energy) but dry, at and wet of optimum and the ML-2x sensor was used in each of the samples.…”

Section: Penetration Abilitymentioning

confidence: 99%

“…5). The soil used in this series of measurements exhibits dilation during shear [2] for the densities the samples had. The insertion of sensor rods resembles shear and it is expected therefore to cause dilation of the soil in the vicinity of the sensor rods.…”

Section: Indirect Effect Of Density and Effect Of Sample Receiversmentioning

confidence: 99%

Volumetric water content measurement probes in earth-dam construction

2016

E3S Web Conf.

Abstract. Two frequency domain reflectometry (FDR) probes have been used. They were used on compacted soils both in the laboratory and in the field. Measurements in the laboratory were intended for calibration. The range of densities and types of materials where insertion of the probes can be achieved was investigated first. The effect of sporadic presence of coarser grains and density on these calibrations, once insertion could be achieved, were investigated second. Measurements on laboratory prepared samples with the same moisture content were different when the sample was kept in the mould from when it was extruded from it. Also both these measurements were different from that in a sample of the same density but significantly larger in diameter. It was found that measurements with these probes are affected by dilation exhibited by soil around the rods of the probes during insertion. Readings immediately after insertion of the sensors on samples extruded from their moulds were the ones closer to measured values. These readings combined with total volume and mass obtained from sand-cone tests during the construction of an earth-dam allowed fairly accurate estimation of the dry unit weight but not the gravimetric water content.

Reproduction and long-term monitoring of drying of mudbricks and small mudbrick walls for the preservation of the ancient mudbrick wall of Eleusis

Marinis²,

Toumbakari

et al. 2023

E3S Web of Conf.

The mudbrick wall remains preserved to date in the site of Eleusis are some of the largest preserved in Greece. Following an extensive investigation of the properties of existing mudbricks, material of similar properties from the archaeological site of Eleusis was used to reproduce mudbricks of similardensity with the ancient ones after drying with various concentrations of dry grass also from the archaeological site. Actual mudbricks were reproduced and brought to a final equilibrium condition under climatic conditions practically similar to those in Eleusis. Others were used to trim samples and measuremechanical properties to compare with original mudbricks, others were instrumented with suction and volumetric water content sensors in order to monitor mudbrick drying under climatic conditions and others in order to build small mudbrick walls with mortar from the same soil used to make the mudbricks. These small mudbrick walls included the mudbricks with internally installed suction and volumetric water content sensors and were also constructed with similar sensors in the mortar. This allowed monitoring of drying of the mortar until each whole mudbrick wall came to equilibrium and was then subjected to uniaxial compression under load control. Monitoring of mudbricks and mudbrick walls indicated that the higher the dry grass concentration, the higher the drying rate of the mudbricks; the lower the dry grass concentration the higher the probability of mudbrick cracking during drying; minimum required time for mudbrick and mudbrick wall drying for the particular soil used in the ancient mudbricks is not less than 5 weeks. Finally, uniaxial compression under load control on both samples trimmed from dried mudbricks and mudbrick walls indicated that uniaxial compression strength decreases with increasing dry grass concentration and mudbrick wall strength should be expected in the order of 70-80% that of the cubic samples trimmed from dried mudbricks and subjected to load rate control compression.