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Deep and high-stress mining results in stress transfers onto the previously placed backfill, and mines have recorded several MPa induced backfill stress. Understanding the backfill-rock mass interaction is therefore critical. Previous work considered tabular ore bodies undergoing primarily one-dimensional compression and showed how the backfill reaction curves could be estimated from oedometer laboratory test results. This work considers massive orebodies and develops a similar approach based on isotropic compression curves. Isotropic compression tests exceeding 6 MPa are carried out on samples with 3.0–11.1% binder content, tested at 1-day cure time to 28-day cure time. The compression curve is characterized in three stages: initial elastic compression up to a yield point, followed by a transition stage to the start of a final stage with a linear post-yield compression line in \({\epsilon }_{v}-\text{l}\text{o}\text{g}\left({p}^{\text{'}}\right)\) space. Because these isotropic compression tests are rare (the reported results are the first for Cemented Paste Backfill), attempts are made to relate the isotropic compression test parameters to parameters from the more commonly used Unconfined Compression Strength (UCS) tests. Unifying equations as functions of binder content and cure time are found to determine the initial yield stress and the peak strength from UCS tests. These are then related to the corresponding parameters in isotropic compression. Finally, the slope of the post-yield compression line is found as a function of UCS, thereby enabling complete reconstruction of the isotropic compression response based on parameters from carefully controlled UCS tests, as functions of binder content and cure time. Although the calibrated parameters are specific to the studied mine’s materials, the framework is general and applicable to other mines’ CPBs.

Estimating the as-placed properties of mine backfill is fundamental to optimizing the safety and productivity of underground mines. For Cemented Paste Backfill (CPB) an important consideration is the extent to which self-weight consolidation during deposition may reduce the void ratio and enhance the binder’s effectiveness. Field monitoring and sampling campaigns can help investigate this phenomenon but they are expensive and logistically difficult. Therefore, mesoscale column experiments are performed in the controlled laboratory environment to better understand the coupling between self-weight consolidation and cement hydration. In this paper, columns are backfilled with uncemented paste tailings and with CPB and the pore water pressure, electrical conductivity, and volume changes are monitored during and after backfilling. The pore water pressure profiles at the end of backfilling are compared with an available analytical solution and restrictions on the solution’s validity are identified. Void ratios of samples taken from columns are compared with the ones obtained from field samples and the similarity indicates the filling conditions simulated in the laboratory are representative of field conditions. The changes in void ratio after curing were small compared to the initial void ratio of fresh CPB. The tests’ results help explain why self-weight consolidation during backfilling is not significant at the studied mine, which may be the case for many other mining operations as well.

Alopecia areata (AA), a polygenic and chronic autoimmune disease and there is no definitive cure. We aimed to evaluate latanoprost effects in patients with AA. In this controlled randomized double-blind clinical trial, we enrolled patients with AA randomly assigned to six groups of 18; Group 1 received latanoprost eye drops; group 2 minoxidil 5% solution; group 3 latanoprost eye drops and minoxidil 5% solution; group 4 betamethasone and minoxidil 5% solution; group 5 betamethasone solution and latanoprost eye drops; group 6 (the control group) betamethasone solution. The alopecia severity in patients before and after treatment was assessed by severity of alopecia tool (SALT). One hundred and eight patients, 50% male (mean age: 32.6 ± 10.4) were studied. The overall SALT score decreased in all. After 2 weeks, patients receiving betamethason-minoxidil and betamethason-latanoprost showed more decline in their SALT than other groups. In final, there was statistically significant difference among betamethasone-latanoprost group with minoxidil, betamethasone-minoxidil and betamethasone groups. Regrowth was higher in latanoprost and betamethasone-latanoprost groups than minoxidil. Topical latanoprost added to therapeutic efficacy of topical betamethason and minoxidil in treating patchy AA, suggesting it being beneficial and safe adjuvant therapy and add to efficacy of topical treatments without any adverse effects.

Cemented paste backfill (CPB) has been widely used as local and regional underground support to reduce host rock wall closure in mined-out areas and also to reduce rockfall and rockburst incidents. However, analyzing the rock mass—CPB interactions in the first month after backfill placement must account for the CPB’s time-dependent strength, stiffness, and volume change characteristics during binder hydration. This article presents the first such comprehensive study made for CPB from the Williams mine in Ontario, Canada. Monotonic isotopically consolidated drained compressive triaxial tests were conducted on cured CPB specimens using the lubricated-ends test technique. The specimens had 3.0–7.5% Cement Content (CC); Curing Times (CTs) were from 3 to 28 days; and the confining stress ranged from 25 to 350 kPa. During shearing, all tests exhibited an initial contractive phase leading to a Characteristic State (CHS or point of volumetric strain reversal) followed by dilation with a maximum dilation rate corresponding to peak stress at the Failure State (FS). Both CHS and FS are adequately described by the Mohr–Coulomb criterion and a framework formulation was proposed to predict the evolution of CHS and FS based on CC and CT. Furthermore, the volumetric strains at CHS and FS can be defined as linear functions of the respective axial strains at the CHS and FS. Quantification of the observed behaviors through these functional relationships can help develop future constitutive models that better represent CPB’s transient response to triaxial stress loading while curing, which is essential to understanding as-placed backfill properties and its interaction with surrounding rock mass.

The hybrid failure is a coupled failure mechanism under the action of tensile and shear stresses. The failure is critical in cemented paste backfill (CPB) since there are no visible signs prior to the failure. Few studies have been conducted on the coupled stress response of CPB. This is most likely due to a lack of suitable laboratory equipment and test procedures. This paper presents a new punching shear apparatus to evaluate the hybrid failure of CPB. We harness two-dimensional finite element analysis (FEA) for supplementing experimental study in providing stress transformation, deformation, and possible failure mechanisms. Our study suggests that the coupled stress is a combination of tensile and shear strength in function of the angle of the frustum. The strengths measured by the coupled stress are comparable to those measured by direct shear and tensile strength tests, in which the strength properties of CPB are curing time and binder content dependent. The FEA results substantiate the effectiveness of proposed model for predicting the hybrid failure of CPB.

Deep and high-stress mining relies on backfill to support exposed host rock surfaces, but the backfill response to isotopic compression is virtually unknown. This paper studied the properti...

Two types of Ottawa sand (ASTM C778 #20–30 graded sand, denoted OS1, and C109 ASTM #C778 graded sand, denoted OS2) with different particle size distributions were tested in a series of dynamic uniaxial strain experiments using a modified split Hopkinson pressure bar (SHPB) system. The pulse shaper technique was employed to achieve the dynamic force balance and constant strain rate in the sand specimen. The effects of the strain rate, initial void ratio and moisture on the dynamic compression response of sand were examined. Two types of dynamic behavior occurred in the dry sand: solid-like and fluid-like behavior. The OS1 samples exhibited a fluid-like response at all initial void ratios, whereas the OS2 samples exhibited a solid-like response for all void ratios. This difference between the two sands may be due to the difference in the particular size distributions of OS1 and OS2. The initial elastic response of the dry sand samples seemed to be independent of the strain rate. The strain rate effects became more apparent after particle crushing and particle rearrangement began. Under a high degree of saturation, the strain rate effects were immediately apparent, even at lower strains. The dynamic response of sand was remarkably linear until the peak strain was reached.

Backfill in deep and high-stress mining controls stress redistributions and provides rock mass support on the mine-wide scale. The advantages of Cemented Paste Backfill (CPB) include fastest filling rate (including the potential for continuous backfilling), uniform as-placed properties, and tight filling of the mined voids. Numerically analyzing CPB response during filling, curing, and subsequent mining must account for evolving strength properties arising from ongoing hydration processes , particularly in the first 3–28 days. This work uses Brazilian tensile strengths , a specially designed zero-effective stress Unconfined Compressive Strength (UCS) test, and drained confined triaxial test results to characterize the non-linear failure envelope for a typical low sulfide content CPB with binder contents from 3.0% to 7.5%, and strength evolution from 3 to 28 days. Power functions in terms of Cement Content (CC) and Cure Time (CT) are calibrated using the entire data range and then used to determine UCS (ranging approximately from 55 kPa at 3%/3-day to 460 kPa at 7.5%/28-day) and tensile strength (ranging approximately from 8 kPa at 3%/3-day to 60 kPa at 7.5%/28-day). Other power functions are then used for the failure envelopes and show that confining stress dependency becomes increasingly nonlinear with increasing CC, with the exponents ranging from 0.874 at 3% CC to 0.789 at 7.5% CC. The formulated strength envelopes with hydration time dependency are an improvement on existing models for CPB strength (typically based on Mohr-Coulomb with time-dependent parameters) and can be conveniently incorporated into numerical analysis codes.

The estimation of the bearing capacity of embedded foundations in cohesive soils has important civil engineering applications both onshore and offshore such as bored piles, skirted foundations, spudcan footings and so on. This topic has been extensively investigated numerically in the literature, where it is mostly stated that the commonly used semi-empirical relations in the industry for example by Skempton are extremely conservative. Such conclusion may not be accurate if two relatively neglected aspects are investigated: (a) rigidity index, ratio of shear modulus to undrained shear strength of soil and (b) limited tensile strength of soil. A finite-element analysis was conducted. The influence of these factors on bearing capacity enhancement is presented. Simple algebraic expressions are provided to guide practitioners.

Considering the fact that Iran is one of the world's most seismically active countries, the use of lightweight concrete in constructions is reasonable which will reduce the seismic effective weight of the structures and therefore they will be less imposed to earthquake forces. So it is important to study about using lightweight concrete in construction in Iran. Considering the importance of the possibility of industrial production of light weight concrete, the cost effectiveness of design plays an important role in the approval or rejections of such plans. In this study the effect of the ratio of cement paste volume to the aggregate volume on the compression strength, density, viscosity and cost effectiveness of nine different mixture plans is studied. The cost effectiveness of the plans is adjusted by a cost factor based on the average price of materials. Due to the fact that the main goal of our examination is to observe the effects of the volume of binding materials in the plans under study, the water-cement ratio and type of cement (Portland 425-1) is kept constant while the total volume of the cement paste is varied and its effects on the factors noted above is studied. The aggregate materials of these designs include artificial aggregate (Lica) which are tested based on three different types of grading: 1-Light Coarse aggregate+s and 2-Light Fine aggregate+sand 3-Mixture of Coarse and Fine aggregate+sand.

This article presents the results of a laboratory study on the variation of specific gravity (Gs) and void ratio (e) in a cemented paste backfill (CPB) with different cement contents and curing times. CPBs consist of a mixture of mine tailings, portland cement, and mine process water. In this study, a helium stereopycnometer device was used to determine Gs for specimens having cement contents of 3.0, 5.3, 7.5, and 11.1 % by the weight of dry tailings. Curing times of 4 h, 1, 3, 7, 14, and 28 days were considered for testing purposes. In total, 240 helium stereopycnometer tests were conducted in this study, which shows that Gs decreases in the CPB specimens as specimens cure over time and the cement hydrates. Furthermore, 96 tests were conducted to determine e of the CPB specimens with different combinations of cement contents and curing times. The results of these tests indicate that similar to Gs, e decreases with an increase in curing time as the specimens hydrate. The reduction in Gs and e is attributed to the formation of hydration products, which have a lower density than the cement and fill the void space between the particles. The results show that the variation of Gs that is due to the hydration process should be considered in the calculation of e; otherwise, this physical property, especially for specimens with high cement contents, is overestimated.