Wave Velocity Test Research Articles

Mid-scale biocemented soil columns via enzyme-induced carbonate precipitation (EICP)

Biocemented soil columns were created at a reduced scale (mid-scale) using enzyme-induced carbonate precipitation (EICP) as a prelude to field scale deployment. Approximately 0.3 m diameter × 0.75 m long columns were created using a tube-à-manchette grouting technique in 0.6 m × 0.6 m × 1.2 m boxes filled with a dry washed quarry sand. Treatment solution composition and treatment protocol, including number of cycles of treatment and time interval between cycles, were established based upon laboratory testing. The urease enzyme used in the treatment solution was extracted from jack beans in a just-in-time manner on site. The biocemented soil columns were characterized in situ using shear wave velocity, needle penetrometer and pocket penetrometer testing, dimensional measurements, and by unconfined compression strength (UCS) and carbonate content measurements on specimens recovered from the columns. The in situ measurements indicated the target UCS of 500 kPa was achieved. However, the UCS tests on recovered specimens had inconsistent results, which may be attributed to sample disturbance. Overall, the results demonstrate that EICP is a viable method for creating biocemented soil columns for ground improvement.

Physico-mechanical characterization of schists in Tazzeka complex [Taza Province, Eastern Morocco

This paper presents the first results of a physicomechanical reconnaissance campaign on the schist of the Tazekka primary massif in northeast Morocco. The main objective of this work is to assimilate the mechanical behavior of those schists, propose characteristic correlations via more accessible tests and assess the technical and economic opportunities for the exploitation of this deposit. For this purpose, a total of 29 sites were selected according to a multi-criteria study. Thus, 203 sampled specimens were subjected to several characterization trials, namely the Los Angeles test, Micro Deval test, Uniaxial compression test, Fragmentability test, Degradability test and Ultrasonic wave velocity test. On the first hand, the results highlight the potential of these rocks as road aggregates according to European standards specifically for low traffic roads constituting 70% of the local network. On the second hand, The large amount of collected data allowed the proposal of representative correlations between the different mechanical tests relating to the compression and shearing ultrasonic waves velocities. Finally, this experimental study constitutes a first orientation work in favor of state services to update their technical approaches, which generally prohibit the reuse of the evolving rocks.

Investigation on Shear Wave Velocity and Triaxial Mechanical Performance of Tailings Core from Tailings Dam

The physical and mechanical parameters of tailings are important to study the stability of tailings dams (TDs). In this study, a series of laboratory experiments (shear wave velocity, triaxial compressive, and peak strain strength testing) were conducted to obtain the mechanical properties of tailings from TD. The results showed the following. (1) The linear function fitting could characterize the quantitative relationship between shear wave velocity and hole depth. (2) The corresponding static pressure coefficient increased as the confining pressure increased. The exponential fitting could characterize the quantitative function relation between the static pressure coefficient and the confining pressure. (3) The cohesion and internal friction angle of the tailings sample were 20 kPa and 41°, respectively, and the logarithmic fitting could better characterize the quantitative relation between shear peak strength and confining pressure. The results of this study can provide important references for further research on the stability of TD.

A novel PSO-KELM based soil liquefaction potential evaluation system using CPT and Vs measurements

Evaluation of soil liquefaction potential is an essential step in geotechnical engineering design. This study presents a novel soil liquefaction potential evaluation system using cone penetration test (CPT) and shear wave velocity test (Vs) measurements. To this end, a new hybrid machine learning model called PSO-KELM model that combines the kernel extreme learning machine (KELM) with particle swarm optimization (PSO) is developed to assess soil liquefaction potential. Then, the PSO-KELM based searching technique is adopted to search the nonlinear relationship between CRR and CPT along with Vs measurements. Finally, a new probabilistic model is developed by considering the model uncertainty and sampling bias based on weighted maximum likelihood estimation. Results demonstrate that the performance of PSO-KELM model is significantly better than that of many other machine learning methods. The cyclic stress ratio, equivalent clean sand normalized cone tip resistance, normalized friction ratio, fines content, and soil behavior type are the recommended input variables for PSO-KELM model. The combined use of CPT and Vs measurements can significantly improve the prediction accuracy since it can more fully reflect soil liquefaction phenomenon. The proposed evaluation system can improve the performance of seismic CPT (SCPT) in soil liquefaction potential evaluation.

Experimental research on cyclic impact load of concrete during curing period

In order to study the influence of cyclic impact load on the compressive strength of concrete during the curing period, we used a self-made drop-weight impact test device to conduct a daily impact test on C40 concrete specimens with a curing period of 28 days. At the same time, the longitudinal wave velocity test of the test block before and after the impact was carried out, and the 28-day uniaxial compressive strength of the concrete test block was finally measured. The results show that the cyclic impact load during the curing period will cause internal damage to the concrete, and the uniaxial compressive strength is significantly reduced; the acoustic wave test results show that the damage of the concrete under the impact energy of 11.76kJ, 5.88kJ, 7.84kJ, and 8.82kJ is 0.035, 0.022, 0.031, 0.031. The uniaxial compressive strength values after 28 days decreased by 11.93, 4.68, 7.6, 10.23 MPa. There is a positive correlation between impact load, damage and reduction in compressive strength.

A new approach for constructing two Bayesian network models for predicting the liquefaction of gravelly soil

Many studies have indicated that the triggering conditions for gravelly soil liquefaction are different from those for sandy soils. However, the existing prediction methods and models do not consider the differences. Moreover, most approaches of constructing Bayesian network (BN) models for predicting seismic liquefaction based on domain knowledge or data-driven are either too subjective or too objective, resulting in suboptimal structures. Therefore, to solve these shortcomings, two new BN models for predicting gravelly soil liquefaction are constructed using a new hybrid approach combining the maximal information coefficient and domain knowledge based on the dynamic penetration test and shear wave velocity test databases. The performance of the proposed hybrid approach is validated by comparing other existing modeling approaches, and two new BN models performed much better than other models in both two databases compared with the existing models or methods for predicting gravelly soil liquefaction in the training, validation, and testing sets. Furthermore, the differences and advantages of all methods or models mentioned in this paper are discussed, and factor sensitivity analysis in the BN models illustrates that those triggering conditions different from sandy liquefaction are worth considering in the prediction of gravelly soil liquefaction.

Discussion on the Theoretical Basis for Cross-Over Method Applied to Downhole Wave Velocity Test

At engineering practice, the theoretical basis for the cross-over method, used to obtain shear wave arrival time in the downhole method of the wave velocity test by surface forward and backward strike, is that the polarity of P-wave keeps the same, while the polarity of S-wave transforms when the direction of strike inverted. However, the characteristics of signals recorded in tests are often found to conflict with this theoretical basis for the cross-over method, namely, the polarity of the P-wave also transforms under the action of surface forward and backward strike. Therefore, 3D finite element numerical simulations were conducted to study the validity of the theoretical basis for the cross-over method. The results show that both shear and compression waves are observed to be in 180° phase difference between horizontal signal traces, consistent with the direction of excitation generated by reversed impulse. Furthermore, numerical simulation results prove to be reliable by the analytic solution; it shows that the theoretical basis for the cross-over method applied to the downhole wave velocity test is improper. In meanwhile, numerical simulations reveal the factors (inclining excitation, geophone deflection, inclination, and background noise) that may cause the polarity of the P-wave not to reverse under surface forward and backward strike. Then, as to reduce the influence factors, we propose a method for the downhole wave velocity test under surface strike, the time difference of arrival is based between source peak and response peak, and numerical simulation results show that the S-wave velocity by this method is close to the theoretical S-wave velocity of soil.

Relationship Between Central Artery Stiffness, Brain Arterial Dilation, and White Matter Hyperintensities in Older Adults: The ARIC Study-Brief Report.

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Experimental research on geotechnical engineering characteristics of coral reef in Xisha Islands

Coral reefs are widely distributed in Xisha Islands, which have special engineering properties. Coral reef geology from top to bottom is coral sand, coral gravel, coral reefs calcareous rock. Coral sand and coral gravel have the characteristics of mixed size particles, alternating accumulation of sand and gravel, great change of density and gradually coarsening from top to bottom. Coral reefs calcareous rocks are composed of loose bioclasts cemented, some of them are dense, and some of them are semi-cemented and weakly cemented. The geological age of the Xisha Islands within 50m was determined by carbon-14 radioisotope isotopic test. The bearing capacity and deformation characteristics of coral sand and coral gravel were analyzed by plate loading test, heavy dynamic penetration test, extra-heavy dynamic penetration test and standard penetration test. The physical and mechanical characteristics of coral reefs calcareous rock were studied by longitudinal wave velocity test, density test, porosity test and uniaxial compressive strength test.

A gradation-dependent particle shape factor for characterizing small-strain shear modulus of sand-gravel mixtures

In this study, a series of shear wave velocity tests were conducted on two types of sand-gravel mixtures with a wide range of particle size distributions. The effect of the particle shape on the small-strain shear modulus (Gmax) was investigated using a customized, large-scale triaxial apparatus. The results showed that Gmax increases with the decrease in particle roundness when the uniformity coefficient (Cu) is less than a certain value. However, this increasing trend gradually flattens with the further increase of Cu. Thus, the effect of particle shape on the Gmax varies with the particle gradation. The performances of six relationships proposed in the literature for predicting Gmax were compared and evaluated in terms of their predictive capabilities. An empirical Gmax model based on the Hardin and Black equation was proposed by including a Fourier-based shape factor modified by Cu. The model can characterize the difference in the variation of Gmax with Cu due to different particle shapes and was thereafter validated. Furthermore, the model serves as a reference guide for estimating the Gmax of soils with various particle size distributions through their particle characteristics.

A New Rock Brittleness Index Based on the Characteristics of Complete Stress–Strain Behaviors

Rock brittleness is an essential mechanical property, which plays a significant role in rock classifications and rockburst risk evaluations. To overcome the problems associated with the traditional brittleness indexes not comprehensively charaterizing the rock strength and deformation behaviors, this study systematically summarized the existing rock brittleness indexes. Then, a novel brittleness index (BICSS) based on the complete stress–strain curves of rock under different confining pressures was proposed. Its advantages included innovatively considering the characteristic stresses and strains at the stage of crack initiation, the peak points, and residual points. The index also described the stress growth rates from the pre-peak crack-initiation stress to the peak stress points, as well as the stress drop rates from the peak stress to the residual stress points. This study conducted uniaxial and triaxial compression tests of metamorphic sandstone, granite, and gneiss obtained from a deeply buried long-line tunnel group. The aforementioned tests were combined with wave velocity tests and thin-section identification tests using polarizing microscopy techniques. The reliability and applicability of the index were then successfully verified. The results showed that the BICSS could not only quantify and classify the brittleness characteristics of different rock types and characterize the confining pressure inhibition behaviors of rock brittleness, but could also comprehensively express the influences of homogeneity, mineral compositions, and particle sizes on the rock brittleness. Finally, through the parameter sensitivity analysis of the BICSS, the influences of subjective errors in the results of the cracking initiation stress and strain values caused by the different selections during the linear elastic phase could be successfully excluded, resulting in the further verification of the stability of the BICSS.

Study on wave velocity characteristics and compressive strength of concrete under different water pressure

In order to study the internal damage and static compressive strength of concrete under different water pressures, the wave velocity test and compressive test were carried out by NN-4B non-metallic ultrasonic testing analyzer and electro-hydraulic servo testing machine. The test results show that the high water pressure of concrete has an adverse impact on the development of its internal structure, and with the increase of high water pressure level, the slower the longitudinal wave passes through the specimen, the more serious the damage and deterioration of concrete, and the compressive strength decreases gradually with the increase of water pressure.

The effect of curing conditions on the mechanical properties of SIFCON

In this study, the effect of curing conditions on the mechanical properties of slurry infiltrated fiber reinforced concrete (SIFCON) was investigated. For this purpose, SIFCON samples containing 4% and 8% steel fiber with two different aspect ratios were produced. The samples were subjected to three different curing types, namely standard, dry and accelerated curing methods. Ultrasonic wave velocity, flexural strength, fracture toughness, compressive strength, impact resistance and capillary water absorption tests were performed on the samples. The highest flexural strength was found to be achieved in the samples with an aspect ratio of 55 and a content of 8% steel fiber. The most suitable curing method was determined as the standard curing method and the best flexural strength was achieved at the rate of 8%. According to the test results, the best strength properties were achieved in the samples exposed to the standard curing method. In addition, the samples exposed to the accelerated curing method showed satisfactory values. The accelerated curing method can be used as an alternative in SIFCON production especially in applications requiring mass production.

Predicting the small strain shear modulus of coarse-grained soils

Coarse-grained soils are important geotechnical materials widely used in construction. The contribution of particle size distribution on the small strain shear modulus Gmax of coarse-grained soils has not yet been fully recognized. This paper presents an experimental investigation into the effects of the uniformity coefficient Cu and the mean particle size D50 on the small strain shear modulus of coarse-grained soils. To this end, a series of shear wave velocity tests were conducted at different confining stresses and void ratios on reconstituted specimens covering a wide range of particle size distributions. All tests were performed by taking advantage of a custom-developed measurement device in a large-scale triaxial apparatus. The results demonstrate that Cu and D50 have pronounced but opposite effects on Gmax. Specifically, Gmax decreases with Cu and increases with D50. The effects of Cu and D50 were then quantified to generate two types of empirical equations, type-A and type-B, that are representative of a broad family of Gmax equations accounting for the influence of particle size distribution. The equations are tuned based on model parameters A, x and n. In both equations, n is a function of Cu. The difference between the two types of equations is that x is the function of Cu and D50 and A is the function of Cu in the type-A equation, while x is constant and A is the function of Cu and D50 in the type-B equation. The proposed equations for predicting Gmax were used to produce acceptable estimates for both coarse-grained soils in this study and from existing literature. The findings acquired from this study are expected to provide a reference for estimating the small strain shear modulus of coarse-grained soils at the beginning of the project when the test data have not yet been obtained.

The burden and predisposing factors of non-communicable diseases in Mashhad University of Medical Sciences personnel: a prospective 15-year organizational cohort study protocol and baseline assessment

BackgroundThe rising burden of premature mortality for Non-Communicable Diseases (NCDs) in developing countries necessitates the institutionalization of a comprehensive surveillance framework to track trends and provide evidence to design, implement, and evaluate preventive strategies. This study aims to conduct an organization-based prospective cohort study on the NCDs and NCD-related secondary outcomes in adult personnel of the Mashhad University of Medical Sciences (MUMS) as main target population.MethodsThis study was designed to recruit 12,000 adults aged between 30 and 70 years for 15 years. Baseline assessment includes a wide range of established NCD risk factors obtaining by face-to-face interview or examination. The questionnaires consist of demographic and socioeconomic characteristics, lifestyle pattern, fuel consumption and pesticide exposures, occupational history and hazards, personal and familial medical history, medication profile, oral hygiene, reproduction history, dietary intake, and psychological conditions. Examinations include body size and composition test, abdominopelvic and thyroid ultrasonography, orthopedic evaluation, pulse wave velocity test, electrocardiography, blood pressure measurement, smell-taste evaluation, spirometry, mammography, and preferred tea temperature assessment. Routine biochemical, cell count, and fecal occult blood tests are also performed, and the biological samples (i.e., blood, urine, hair, and nail) are stored in preserving temperature. Annual telephone interviews and repeated examinations at 5-year intervals are planned to update information on health status and its determinants.ResultsA total of 5287 individuals (mean age of 43.9 ± 7.6 and 45.9% male) were included in the study thus far. About 18.5% were nurses and midwives and 44.2% had at least bachelor’s degree. Fatty liver (15.4%), thyroid disorders (11.2%), hypertension (8.8%), and diabetes (4.9%) were the most prevalent NCDs. A large proportion of the population had some degree of anxiety (64.2%). Low physical activity (13 ± 22.4 min per day), high calorie intake (3079 ± 1252), and poor pulse-wave velocity (7.2 ± 1.6 m/s) highlight the need for strategies to improve lifestyle behaviors.ConclusionThe PERSIAN Organizational Cohort study in Mashhad University of Medical Sciences is the first organizational cohort study in a metropolitan city of Iran aiming to provide a large data repository on the prevalence and risk factors of the NCDs in a developing country for future national and international research cooperation.

Peripheral Arterial Stiffness Increases the Risk of Progression of Renal Disease in Type 2 Diabetic Patients.

Aims: Our aim was to investigate the effects of peripheral arterial stiffness on the risk of progression of renal disease in patients with type 2 diabetes (T2D).Methods: This was a single center, retrospective cohort study. Brachial-ankle pulse wave velocity (baPWV) tests were performed on T2D patients in 2015. Increased arterial stiffness was defined as baPWV of ≥ 1800 cm/s. We applied criteria for progression of renal disease according to EMPA-REG OUTCOME trial.Results: In total, 186 patients were enrolled in the final study. The mean age was 59.1 years and male:female ratio was 1.73:1. Thirteen (7%) patients progressed to renal disease during the average follow-up time of 35.3 months. In particular, the risk of progression to macroalbuminuria was significantly higher in the baPWV ≥ 1800 cm/s group (HR 6.216, p = 0.020). Individuals with a baPWV of ≥ 1800 cm/s (when comparisons were adjusted for age, sex, blood pressure, diabetes duration, eGFR, and use of renin-angiotensin system inhibitors) had a significantly higher risk of the progression of renal disease (HR = 8.480, p = 0.014).Conclusion: These results suggest that peripheral arterial stiffness (baPWV ≥ 1800 cm/s) may be a risk factor for the progression of renal disease in T2D patients.

Early Vascular Aging and Risk Factors Among a Population Aged 50 and Below in Kailuan Study

Abstract Background To examine the frequency of early vascular aging and risk factors in an adult population with age ≤50 years old in Kailuan. Methods A total of 21,952 subjects aged ≤50 years without previous history of cardiovascular and cerebrovascular diseases and having completed brachial-ankle pulse wave velocity test in 2010–2016 were recruited. The mean plus 2 standard deviations (mean + 2SD) of brachial-ankle pulse wave velocity in 1,813 healthy population without hypertension, diabetes, dyslipidemia, and smoking were calculated and used as the reference value for early vascular aging. The stepwise regression multivariate logistic regression model was used to analyze the influencing factors for early vascular aging in different age and gender groups. Results The average detection rate of early vascular aging in this population was 15.0% with 12.9% in 30 years or less, 14.8% between 30 and 40 years, and 15.6% between 40 and 50 years. Furthermore, age, male, resting heart rate, high sensitivity C-reactive protein, smoking, hypertension, and diabetes were risk factors for early vascular aging with odds ratio values (95% confidence interval) of 1.02 (1.01–1.03), 2.51 (2.10–3.00), 1.04 (1.03–1.04), 1.09 (1.05–1.13), 1.11 (1.04–1.20), 1.05 (1.00–1.11), 3.55 (3.13–4.03), and 1.69 (1.38–2.08), respectively. The risk factors for early vascular aging in women with gestational hypertension were 4.27 times higher than those in women without (95% confidence interval 1.34–13.53). Conclusions The frequency of early vascular aging is 15.0% in adult population ≤50 years old. Risk factors for early vascular aging include age, male, resting heart rate, high sensitivity C-reactive protein, smoking, hypertension, diabetes, and in women, the pregnancy-induced hypertension.

Sensitivity Analysis in the Estimation of Mechanical Parameters of Engineering Rock Mass Based on the Hoek–Brown Criterion

Geological strength indexGSI, disturbance factor (D), material constantmi, and uniaxial compressive strengthσciof the intact rock are essential input parametersIPsof the Hoek–BrownH−Bcriterion. Mechanical parametersMPsof the engineering rock mass, including elastic modulusE, cohesionc, and internal friction angleφestimated by the H–B criterion, and the predicted excavation response of surrounding rock, including the displacement and excavation damage zoneEDZbased on the MPs, are of high relevance with the four IPs of the H–B criterion. In this paper, the deep and huge underground cavern excavated in basalt from a hydropower station under construction in the southwest of China is used to analyse the sensitivity of the IPs on the MPs, the displacement, and EDZ of the surrounding rock mass. Firstly, the H–B criterion is applied to estimate the MPs, among which the IPs are obtained from a series ofin situand laboratory tests, including borehole camera observation, wave velocity test, uniaxial and triaxial compression tests, and so on. Secondly, the sensitivity relationships between IPs, MPs, and prediction results of displacement and EDZ are established and described quantitatively by the sensitivity factor (si). Results show that the MPs of the rock mass are more sensitive toGSIandD⋅GSIandσciare high-sensitivity parameters affecting the displacement and EDZ. Finally, the variations in the estimated MPs and associated prediction results concerning excavation response, which are caused by the uncertainties in the determination of the IPs, are further quantified. This study provides a straightforward assessment for the variability of the rock mass parameters estimated by the H–B criterion. It also gives a valuable reference to similar geotechnical engineering for the determination of rock mass parameters in the preliminary design.

A Modified Model for Predicting the Strength of Drying-Wetting Cycled Sandstone Based on the P-Wave Velocity

The drying-wetting cycles caused by operation of the Three Gorges Reservoir have considerable effect on the deterioration of reservoir bank rock mass, and the degradation of reservoir rock mass by the drying-wetting cycle is becoming obvious and serious along with the periodic operation. At present, the strength of the rock prediction research mainly focuses on the uniaxial strength, and few studies consider the drying-wetting effect and confining pressure. Therefore, in this paper, typical sandstone from a reservoir bank in the Three Gorges Reservoir area is taken as the research object, while the drying-wetting cycle test, wave velocity test and strength test are carried out for the research on the strength prediction of sandstone under the action of the drying-wetting cycle. The results show that the ultrasonic wave velocity Vp of the sandstone has an exponential function relation with the drying-wetting cycle number n, and the initial stage of drying-wetting cycles has the most significant influence on the wave velocity. Under different confining pressures, the compressive strength of sandstone decreases linearly with the increase of the drying-wetting cycle numbers, and the plastic deformation increases gradually. The damage variable of the sandstone has a power function relation with the increase of drying-wetting cycle numbers. A traditional strength prediction model based on P-wave velocity was established combined with the damage theory and Lemaitre strain equivalence hypothesis; in view of the defects of the traditional strength prediction model, a modified model considering both the drying-wetting cycle number and confining pressures was proposed, where the calculated results of the modified model are closer to the test strength value, and the prediction error is obviously decreased. This indicated that the modified model considering the drying-wetting cycle number and confining pressure is reasonable and feasible.

A Correlation for Estimating LCPC Abrasivity Coefficient using Rock Properties

Rock abrasivity, as one of the most important parameters affecting the rock drillability, significantly influences the drilling rate in mines. Therefore, rock abrasivity should be carefully evaluated prior to selecting and employing drilling machines. Since the tests for a rock abrasivity assessment require sophisticated laboratory equipment, empirical models can be used to predict rock abrasivity. Several indices based on five known methods have been introduced for assessing rock abrasivity including rock abrasivity index (RAI), Cerchar abrasivity index (CAI), Schimazek’s abrasivity factor (F-abrasivity), bit wear index (BWI), and LCPC abrasivity coefficient (LAC). In this work, 12 rock types with different origins were investigated using the uniaxial compressive strength (UCS), Brazilian test for tensile strength, and longitudinal wave velocity and LCPC tests, and microscopic observations were made to obtain a correlation for estimating the LCPC abrasivity coefficient by conducting the conventional rock mechanics tests. Using the equivalent quartz content, velocity of longitudinal waves, and rock brittleness index, a linear correlation was obtained with a coefficient of determination (R2) of 93.3% using SPSS in order to estimate LAC.