Nuclear Tests Research Articles

On Magnitudes and Inferred Yields of the 39 Underground Nuclear Test Explosions at the Novaya Zemlya Test Site

ABSTRACT We review the previously compiled seismic magnitudes for underground nuclear explosions at the Union of the Soviet Socialist Republics Novaya Zemlya Test Site, and analyze these data in the context of published details about individual tests and official Russian reports of annual cumulative explosive energy release at the test site. We derive relationships between teleseismic body wave magnitude mb and explosive yield Y by predicting the yield of each test using mb and minimizing the difference between predicted and reported annual cumulative yield. A linear relationship between mb and logY with a slope of 0.82 provides a good fit to the annual total yield, with a root mean square (rms) misfit of 0.095 logY units. A spectral magnitude relationship based on the explosion source model of Mueller and Murphy (1971) with a single-free-parameter provides a slightly better fit. For the 10 tests for which individual yields can be directly deduced from the official reports, the rms misfit of reported yields is less than 0.1 logY units or about 25%. More complex relationships that differentiate between the northern and southern test areas, or take account of variations in the scaled depth of burial, do not provide substantially better fits to the reported yields.

Asbestos-related cancer in naval personnel: findings from participants in the British nuclear tests 1952–1967

Asbestos-containing materials (ACM) were present in British and Australian naval vessels throughout the twentieth century. The aim of this study was to identify and quantify the incidence of cancer in naval personnel from onboard asbestos exposure. Subjects were four cohorts of subjects who had served in the armed forces of the United Kingdom and Australia in the 1950s and 1960s. All cohorts had previously been studied, three of them in relation to radiation exposures from British nuclear testing. Comparisons of SIRs between services were made to identify cancers attributable to asbestos exposure. Excess mesotheliomas were found in naval personnel in all cohorts. In all but one cohort the lung cancer incidence was highest in navy personnel. Comparison of other smoking-related conditions indicated that the excess in navy personnel was not smoking-related. The relatively high SIRs for mesothelioma and the occurrence of deaths from asbestosis were indicative of high levels of asbestos exposure, with an expectation of cases of asbestos-related lung cancer. The findings are consistent with the occurrence of significant excesses of mesotheliomas. In addition, notwithstanding some inconsistencies in the results between the cohorts, we estimated that approximately 27% of lung cancers in Australian seamen and 12% in British seamen were related to onboard asbestos exposure.

Typical and atypical chest pain: an equivocal and dangerous definition

Abstract Background The traditional classification of stable chest pain into typical, atypical and non anginal1 is equivocal and can lead to doctor's decisions and patient's perception that do not correspond to the real importance of the clinical picture. Methods In the last 15 years, 3,588 outpatients, aged >35 years (mean 64±9, female 55%) were evaluated for stable chest pain reported for more than 48 hours. We excluded 290 patients with a history of myocardial infarction or angina pectoris, heart failure, valve diseases or any other major cardiovascular event, or ECG signs of recent ischemia. In the other 3,298 cases we applied the traditional classification of chest pain. All patients were evaluated for the presence of HEART score risk factors² (smoking, obesity, family history of cardiovascular events, hypertension, diabetes, hypercholesterolemia) as well as age. All patients with typical or atypical angina and those with non-anginal pain according to the physician's judgment were evaluated with one or more functional cardiovascular tests (exertion test, nuclear stress tests, stress echo).A follow-up was performed at 6 months and 1 year, for the detection of major cardiovascular events (cardiovascular death, non-fatal heart attack, revascularization, stroke) and non-cardiovascular mortality. Results Table 1 shows the results of chest pain classification and positive functional test. Table 2 shows major events at one year of follow-up stratified according to the initial assessment of chest pain. Table 3 stratifies the events according to the extent of the risk factors and age. It is evident that a positive functional test is also present in 10% of patients with atypical pain and in 4% of those with non-anginal pain. Patients with typical pain undergo revascularization more frequently (39%). The peculiarity of our study is that the prognosis and rate of events do not differ in terms of clinical and ischemic burden among the 3 groups at 1 year of follow-up, except when patients are stratified by risk burden and for age (Table 4). About 1% of patients had a clinical event regardless of the type of pain and the presence of ischemia and 87% of the events involved patients with ≥ 3 risk factors or heavy smokers. Nine percent of all heavy smokers aged <65 years had a major event and are the highest risk group with a peak of 12.5% in those with atypical pain. Conclusions The traditional classification of stable chest pain should be abandoned, as it does not correlate with actual disease burden and prognosis, that appears to be linked to the burden of cardiovascular risk and above all to smoking in patients < 65 years of age, rather than to the clinical and ischemic burden. It will be necessary to evaluate whether the anatomical burden for the search of high-risk coronary lesions improves the prognosis with added value with respect to the treatment of risk factors³.Picture 1Picture 2

Abstract 13988: Post Stress Test High-Sensitivity Cardiac Troponin I in the Evaluation of Patients With Acute Chest Pain for Enhanced Ischemic Risk Assessment: A Pilot Study

Introduction: High-sensitivity cardiac troponin I (hs-cTnI) assays provide comparable diagnostic information that allow for better detection of myocardial injury. However, hs-cTnI release after cardiac stress testing and its potential utility for identifying inducible myocardial ischemia and risk-stratification are unclear. Aim: This pilot study examined integrating hs-cTnI biomarker testing into cardiac imaging stress testing to improve detection of inducible ischemia and aid in risk-stratification in patients with chest pain being evaluated for acute coronary syndrome (ACS). Methods: We prospectively enrolled 200 consecutive adult patients referred by the Emergency Room for cardiac stress testing for evaluation of possible ACS. A venous blood sample was collected between 0.5 and 2 hours post stress testing; cTnI concentrations were measured in-house by high sensitivity methods. Changes from pre-stress test hs-cTnI concentrations were calculated and association with outcome was explored using a logistic regression model. Results: Patient median age was 62 years, IQR 54-70; 49% were women. ACS known risk factors included hypertension 81.5%, cigarette smoking 49.5% and diabetes 33.5%. Median BMI was 31.63 kg/m 2 , IQR 27.24-35.84. Pre-stress test hs-cTnI median levels were 6 ng/L, IQR 5-9, for women (URL <52 ng/L) and 8 ng/L, IQR 6-12, for men (URL <77 ng/L). A total of 121 patients (60.5%) underwent nuclear stress tests, and 79 (39.5%) received echocardiographic stress tests. Of the 191 samples analyzed, 36% revealed increased hs-cTnI levels from pre-stress test values: 33% in nuclear stress tests (median increase 2 ng/L, IQR 1-5), 41% in echocardiographic stress tests (median increase 2 ng/L, IQR 1-5). In the 155 patients with 6 months of follow-up, changes in post-stress test hs-cTnI levels were not significantly correlated to stress test results, percutaneous coronary interventions or death (p=.85). Conclusion: This study provides insight into the potential of hs-cTnI to aid in identifying inducible myocardial ischemia in a real-world, high-throughput setting. Although a subset of patients exhibited modest increases in hs-cTnI post stress testing, overall, these did not appear to be correlated with inducible myocardial ischemia.

Abstract 16644: Unusual Manifestation of Acute Pericarditis in the Setting of Primary Biliary Cirrhosis

Introduction: Primary biliary cirrhosis (PBC) is an immune-mediated liver disease leading to destruction of intrahepatic bile ducts and cirrhosis. However, its association with pericarditis has not been investigated. Here, we describe a case of a female with PBC who presented with severe pericardial disease. Clinical Case: A 57-year-old female with past medical history of primary biliary cirrhosis, thrombocytosis and type 2 diabetes who presented with sudden onset sharp chest pain, worse with movement or breathing. Workup was notable for elevated D-dimer, CT chest with no evidence of pulmonary embolism but did reveal a moderate pericardial effusion, further confirmed on echocardiogram. Nuclear stress test was unremarkable. CRP 13 mg/dL and ESR 82 mm/hr. Given concern for pericarditis, she was started on colchicine and ibuprofen. On further evaluation in clinic, cardiac MRI showed severe LGE and edema consistent with active pericarditis (figure 1) with mild constrictive physiology and worsening inflammatory markers (ESR 95 mm/hr, us-CRP 118mg/L). Therefore, decision was made to start triple therapy with the addition of prednisone. Repeat cardiac MRI 6 months later showed resolution of LGE and pericardial edema (figure 2). Given clinical improvement, patient was tapered off steroids, started anakinra and weaned off ibuprofen and colchicine. She remained on anakinra for two years after which she was transitioned to single therapy with colchicine with no episodes of recurrence. Discussion: PBC commonly exists with liver autoimmune disorders, but its association with pericardial disease has not been investigated. NSAIDs are often used as first-line therapy for pericarditis, but can be detrimental in advanced liver failure, often seen in patients with PBC. Steroid use is not only advantageous in pericardial disease but also in PBC. As a result, it is critical to identify the link between pericardial disease and PBC to determine appropriate therapeutic management.

Abstract 15772: From Agony to Relief: Overcoming Angina Through Endovascular Coiling of the Left Internal Mammary Artery (LIMA) to Pulmonary Artery (PA) Fistulae- A Case Report

Introduction: LIMA to PA fistulae are a rare complication after coronary artery bypass graft (CABG) surgery. We present a patient with angina secondary to a steal syndrome from LIMA-PA fistulae, treated with endovascular coiling. Case: The patient is a 49-year-old active male with coronary artery disease, status post CABG at age 46 with a LIMA graft to the left anterior descending artery, radial artery graft to the first obtuse marginal artery, and saphenous venous graft (SVG) to the posterior descending artery. At age 48, he developed angina and underwent stent placement to the distal right coronary artery after the SVG was found to be occluded. Several months later, he reported dyspnea and chest pain on exertion. An exercise nuclear stress test showed abnormal myocardial perfusion in the anteroseptal region, and he was referred for left heart catheterization (LHC). LHC revealed unchanged native coronary disease, patent LIMA, and a network of collateral vessels from the LIMA feeding into the pulmonary vasculature (Figure 1). The collaterals were not seen on LHC 9 months prior. CT coronary angiography confirmed multiple fistulae originating from the superior aspect of the LIMA graft communicating with the PA (Figure 1). After a multidisciplinary, patient-centered, heart team discussion, he underwent successful endovascular coiling of the collateral branches (Figure 2). Discussion: LIMA-PA fistulae is a rare cause of angina and there is a paucity of literature on management. To our knowledge, coil embolization has been described in roughly 10 cases. Here, we present a successful case of endovascular coiling of collateral vessels leading to symptomatic improvement.

Abstract 18931: A PCSK9 and APOB Double Heterozygote Presenting Phenotypically Similar to Homozygous Familial Hypercholesterolemia

Introduction: Familial hypercholesterolemia (FH) is an inherited disorder associated with mutations in APOB, PCSK9 and LDLR genes. Heterozygous FH (HeFH) generally has one gene mutation. Homozygous FH (HoFH) has two mutations in the same gene and is characterized by vastly elevated plasma LDL-C, accelerated ASCVD and resistance to standard lipid-lowering therapy. Combinations of mutations can present with a phenotype similar to HoFH. We present a double heterozygous patient with unreported mutations in PCSK9 and APOB genes, exhibiting clinical features of HoFH. Hypothesis: Patients with multiple gene mutations for FH can present clinically similar to HoFH and would benefit from novel lipid lowering therapies Methods: 73-year-old female with a history of diabetes and hyperlipidemia presented in 2018 with dyspnea on exertion. Cholesterol (TC) and triglycerides (TG) were 430 and 715 mg/dl respectively, on rosuvastatin 40 mg and omega 3 fatty acids. Physical exam showed arcus senilis. A nuclear stress test showed ST depressions in inferolateral leads but normal scintigraphy. Genetic testing revealed APOB and PCSK9 mutations. She was then treated with rosuvastatin, icosapentyl ethyl, ezetimibe and fenofibrate. TC, LDL, TG and ApoB levels were 463, 236, 747 and >240 mg/dl respectively. Evolocumab was added, with reduction of TC, TG and ApoB levels to 326, 432 and 182mg/dl, despite maximal available therapy. Results: Genetic testing revealed APOB variant NP_000375.2:p.Gln3378His and PCSK9 variant NP_777596.2:pAla544Thr, which were unreported mutations with unknown clinical significance. Genetically, this patient is a double heterozygote but expresses a phenotype similar to HoFH due to a poor response to maximum therapy. Conclusions: Although usually genetically defined, the phenotype of HoFH can present with different genetic variations. Chaudhry et al established genetic diagnosis of HoFH in 0.9% of patients initially diagnosed as HeFH, of which 3 were true homozygotes and 3 were compound heterozygotes. These findings support the idea that various heterozygous combinations of mutations in the genes for LDLR, APOB and PCSK9, may present clinically similar to HoFH. Patients with these mutations could benefit from novel agents such as evinacumab.

Investigation on basic properties and microscopic mechanisms of polyacrylate latex modified cement grouting material for water blocking and reinforcement

Grouting is a highly effective engineering intervention utilized to address water inrush disasters and reinforce weak surrounding rock formations, with the grouting material playing a crucial role in determining the outcomes of grouting operations. To simultaneously meet the requirements of water plugging and reinforcement, a new polyacrylate latex modified cement grout was prepared, consisting of superfine cement, polyacrylate latex, a defoaming agent, and a coagulation accelerator. This study reports on a series of tests conducted to examine the workability, mechanical properties, and microstructures of polyacrylate latex modified cement grout with varying ratios. The experimental results indicate that the addition of polyacrylate latex significantly reduces the bleeding ratio of the grout, as well as improves its groutability and enhances its resistance to dynamic water scouring, particularly under high-flow conditions. The viscosity of the composite grout increases by adding polyacrylate, leading to a decrease in its fluidity. As the proportion of polyacrylate latex increases, the early and final strength of the grout stone body increases while the porosity decreases. The hydration degree of the grout shows a growing trend with the addition of polyacrylate latex based on the observations by low-field nuclear magnetic resonance tests. The modified grout stone body is dense, primarily due to the chemical reaction between calcium ions produced by cement hydration and carboxyl groups produced by the hydrolysis of ester groups on the polyacrylate latex, leading to cross-linking between the inorganic and organic phases and the formation of a complex network structure. Excellent working performance particularly in terms of anti-scour and load-bearing capacity makes polyacrylate modified cement grouting materials highly suitable for use in the simultaneous treatment of water inrush and reinforcement.

Permeability and Cracking of Compacted Clay Liner Improved by Nano-SiO2 and Sisal Fiber

The landfill liner is the last line of defense to protect the soil from damage, but it is difficult to satisfy both impermeability and crack resistance requirements with conventionally compacted clay. This paper proposes a new composite material to enhance the anti-seepage and anti-cracking properties of clay as a solution to this problem. In this Study, the effects of two single amendment materials, Nano-SiO2 (6 dopings) and sisal fiber (SF) (4 dopings), and a composite amendment material (Nano-SiO2+SF), on the permeability and cracking resistance of the improved clay were investigated by infiltration tests and dry-wet cycle tests, respectively. The nuclear magnetic resonance test (NMR) test reveals the microscopic pore changes of soil and explore the reinforcement mechanism. The findings of penetration experiments demonstrate that Nano-SiO2 and SF, both single and composite components, can increase the modified clay's impermeability. The optimum content of Nano-SiO2 is 3%, and its permeability coefficient is 5.09 × 10−8 cm·s−1, which is two orders of magnitude lesser than that of virgin soil. The results of three dry and wet cycle tests showed that the overall trend of fracture length and cracking factor (CIF) increased with the increase of the number of de-wetting. After the third de-wetting of the modified clay, 0.75% Nano-SiO2 + 0.3% SF is the optimal dose, which reduces the fissure length by 19.94 times and CIF by 27.25 times compared with the three de-wetting of the plain clay. As a whole, the data demonstrates that the composite Nano-SiO2 and SF are able to make up for the shortcomings of each component. It can simultaneously improve the anti-seepage and anti-cracking properties of the enhanced clay. The test results provide a certain benchmark for the impermeability and anti-cracking of landfill liners.

Influence of basalt fiber on pore structure, mechanical performance and damage evolution of cemented tailings backfill

To study the influence of the addition of basalt fibers on the mechanical properties, pore structure, and damage evolution characteristics of the cemented tailings backfill (CTB), the uniaxial compression tests, nuclear magnetic resonance tests and scanning electron microscopy analysis were conducted on the CTB with four different content and lengths of basalt fibers. Test results show the following. (1) An increase in the content of basalt fibers will lead to an increase in the proportion of micropores and secondary pores in the CTB, while a decrease in the proportion of macropores. The influence of basalt fiber length on pore structure is not as significant as the content. (2) With the increase of basalt fiber content and length, the peak stress and peak strain of the CTB increase, but the elastic modulus decreases. Basalt fiber can significantly improve the ductility and bearing time of the CTB, with a length of 12 mm and a content of 1.5 % having the best effect. The length of basalt fibers affects macroscopic mechanics more than content. (3) The CTB without fiber have fewer cracks and faster crack propagation speed, while the CTB with fiber have more cracks and slower crack propagation speed. Basalt fibers mainly play a bridging role between hydration products, delaying the failure process of the sample. (4) A damage constitutive model was constructed. The rationality and reliability of the model were verified, and the damage evolution law of CTB was analyzed. The content and length of basalt fibers have a positive impact on damage evolution.

Comorbid Conditions in Persons Exposed to Ionizing Radiation and Veterans of the Soviet-Afghan War: A Cohort Study in Kazakhstan.

This study investigated the prevalence and characteristics of comorbid conditions in patients exposed to ionizing radiation and those who were involved in the Soviet-Afghan war. This study analyzed the frequency and spectrum of morbidity and comorbidity in patients over a long-term period (30-35 years) following exposure to ionizing radiation at the Semipalatinsk nuclear test site or the Chornobyl nuclear power plant, and among participants of the Soviet-Afghan war. A cohort study, both prospective and retrospective, was conducted on 675 patients who underwent comprehensive examinations. Numerical data were analyzed using the Statistica 6 program. The results are presented as the mean±standard deviation, median, and interquartile range (25-75th percentiles). The statistical significance of between-group differences was assessed using the Student t-test and Pearson chi-square test. A p-value of less than 0.05 was considered statistically significant. We found a high prevalence of cardiovascular diseases, including hypertension (55.0%) and cardiac ischemia (32.9%); these rates exceeded the average for this age group in the general population. The cumulative impact of causal occupational, environmental, and ultra-high stress factors in the combat zone in participants of the Soviet-Afghan war, along with common conventional factors, contributed to the formation of a specific comorbidity structure. This necessitates a rational approach to identifying early predictors of cardiovascular events and central nervous system disorders, as well as pathognomonic clinical symptoms in this patient cohort. It also underscores the importance of selecting suitable methods and strategies for implementing treatment and prevention measures.

Tidal modulation of very-low-frequency and ultra-low-frequency ambient noise levels.

Several years of continuous low-frequency underwater ambient noise data from 0.1 to 125 Hz have been made available for examination by the United Nations Comprehensive Nuclear Test Ban Treaty Organization. Narrow-band noise time records between 0.5 and 10 Hz were selected for study, chosen deliberately to address noise sources tied primarily to the environment. Power spectra of the variable narrow-band time records were found to display sharp spectral lines at fluctuation frequencies that match lunar and solar diurnal and semidiurnal ocean tides.

Microbial involvement in iodine cycle: mechanisms and potential applications.

Stable iodine isotopes are essential for humans as they are necessary for producing thyroid gland hormones. However, there are hazardous radioactive iodine isotopes that are emitted into the environment through radioactive waste generated by nuclear power plants, nuclear weapon tests, and medical practice. Due to the biophilic character of iodine radionuclides and their enormous biomagnification potential, their elimination from contaminated environments is essential to prevent the spread of radioactive pollution in ecosystems. Since microorganisms play a vital role in controlling iodine cycling and fate in the environment, they also can be efficiently utilized in solving the issue of contamination spread. Thus, this paper summarizes all known on microbial processes that are involved in iodine transformation to highlight their prospects in remediation of the sites contaminated with radioactive iodine isotopes.

A Spatial Analysis Model for Proactive Assessment on Radioactive Isotopes in Environment

— In general, no one can escape from radiation. Radiation exists in various forms as minerals in earth and water, cosmic rays in space, radioactive energy in human body, man-made effects as in the form of industrial waste, result of nuclear weapon test, nuclear reactor and medical procedures. The people those who are living closer to the environment where radioactive emission is found to be high, would have a high risk of getting significant health aliments like skin burns and radiation sickness. Moreover people who receive constant exposure to lower level of radiation will susceptible to have cancer and cardio vascular diseases in their life time. The primary motive of the proposed work is to evaluate the concentration of the radioactivity substances, tracking the impact through present and futuristic patterns using deep learning techniques.

Simulated inventory and distribution of 137Cs released from multiple sources in the global ocean

Radioactive cesium (137Cs) is distributed in the world's oceans as a result of global fallout from atmospheric nuclear weapons tests, releases from fuel reprocessing plants, and inputs from nuclear power plant accident. In order to detect future radionuclide contamination, it is necessary to establish a baseline global distribution of radionuclides such as 137Cs and to understand the ocean transport processes that lead to that distribution. In order to aid in the interpretation of the observed database, we have conducted a suite of simulations of the distribution of 137Cs using a global ocean general circulation model (OGCM). Simulated 137Cs radioactivity concentrations agree well with observations, and the results were used to estimate the changes in inventories for each ocean basin. 137Cs activity concentration from atmospheric nuclear weapons tests are expected to be detectable in the world ocean until at least 2030.

Research on the Preparation of Kaolin from Coal Gangue by Flotation Decarburization with Different Collectors

In order to find a better collector for the separation of carbon and kaolin from coal gangue flotation, and to explore the action mechanism of collectors, this paper selected 12 kinds of collectors for systematic comparison, including five non-polar organics with different carbon chain lengths, and polar organic matters with double bonds, triple bonds, benzene, as well as cycloalkyl, ester, carboxyl, and aldehyde groups. The flotation results show that the longer carbon chain (with a carbon atom number of 13~15), the better the flotation effect, the better the effect of the collector with the phenyl group (among the four hydrocarbon groups), and the better the effect of the collector with the ester group (among the three functional groups). In order to explore the flotation mechanism at the microscopic level, the molecular structure of carbon in coal gangue was detected using a solid nuclear magnetic test. Afterwards, the organic macromolecule model of carbon was simulated. Finally, the interaction energy values between carbon and collectors were calculated in accordance with the density functional theory, and the order of the acting force of collectors was obtained, which was consistent with that of the collectors in the macro experiment.

A cytosystematic study of the Dianthus virgineus complex (Caryophyllaceae) in the Central Mediterranean

AbstractEuropean wild carnations (Dianthus) are represented by a high number of taxa organized in unresolved taxonomies. In particular, taxa belonging to the Dianthus virgineus L. complex in the Central Mediterranean have been delimited mainly with qualitative morphological data and still await quantitative investigations, which are vital to understand boundaries and relations among plant diversity groups. Here, we examine the phenotypic features of nuclear genome organization testing for species boundaries in this complex. We have studied the chromosome number, the total haploid length (THL), and the relative genome size (RGS) in 122 populations belonging to 25 out of 33 taxa of the complex. All the studied populations have 2n = 2x = 30 chromosomes, and the THL ranges from 14.09 to 20.71 μm. Genome size estimations support the absence of polyploidization events, but show a certain degree of variation (0.318–0.423 arbitrary units). The RGS variation is not in agreement with current taxonomic treatment, but rather shows a geographical pattern, with higher values in Sicily and Sardinia. No correlation between the THL and the RGS was detected, possibly due to the stable chromosome number and the small size of chromosomes. A number of evolutionary unique groups lower than the number of currently accepted taxa may be hypothesized.

Algorithm development for low level radioxenon 2D spectra analysis: A first case of study using spectral unmixing for a β-γ detector

In the scope of the verification regime of the Comprehensive nuclear Test Ban Treaty, the CEA/DAM is developing new β-γ measurement systems. In order to improve the analysis methods at low statistics, a new multiplicative spectral unmixing algorithm for full-spectrum analysis was tested on a particular setup for different types of mixtures. The reconstructed activities for simulated spectra and the characteristic limits found with this algorithm are compared to the classic ROI analysis method.

Discrimination of Seismic Events in the North Korean Test Site and Surrounding Area Using MDAC Spectral Ratio

ABSTRACT An event of ML 3.7 occurred near the Punggye-ri nuclear test site on 11 February 2022. It was stronger than the known historical earthquakes around the North Korean test site (NKTS). How to accurately identify whether this event and future events near NKTS are explosions or natural earthquakes is worth paying attention to. For moderate and small earthquakes, the regional P/S spectral ratio has the advantage of identifying explosions and earthquakes. However, the P/S spectral ratio depends on magnitude and ray path. Magnitude and distance amplitude correction (MDAC) was proposed and demonstrated to be an effective method to correct magnitude and path effect. Different from the traditional MDAC method, we use explosions to build the MDAC model to reduce the influence of the source radiation pattern. After building the MDAC model, we analyze the Pg/Lg and Pn/Lg spectral ratios of 6 nuclear tests and 60 earthquakes at the NKTS from 2013 to 2021. The results show that the spectral ratio residuals of the 6 nuclear tests are mainly distributed around 0 after correction, whereas the spectral ratio residuals of earthquakes are obviously <0 above 3 Hz and are clearly distinguished from explosions as expected. The Pg/Lg and Pn/Lg spectral ratios of the ML 3.7 earthquake near the NKTS on 11 February 2022 exhibit similar characteristics to historical natural earthquakes. We further discuss the influence of magnitude on P/S spectral ratios. In the NKTS, the differences in the P/S ratio between earthquakes and explosions are similar before and after magnitude correction at 4–8 Hz. Nevertheless, the magnitude correction increases by ∼27% of the difference between explosions and natural earthquakes at 6–9 Hz to better separate explosions from natural earthquakes.

Experimental Study of the Dynamic Characteristics and Microscopic Mechanism of Lightweight Soil Modified with Expanded Polystyrene and Sisal Fibre

With the increasing demand and use of highways, railways and tunnels in China, the phenomena of foundation settlement, uneven deformation and ground cracking caused by the cyclic loading by traffic are becoming increasingly significant. There is now an emphasis on research to prevent or decrease these phenomena by mixing new materials into the soil body. In this study, cyclic loading tests were conducted on lightweight soils modified with expanded polystyrene (EPS) and sisal. A GDS true/dynamic triaxial apparatus was used to study the dynamic elastic modulus and damping ratio of clays with different dosages of EPS and sisal fibre. The modified soil samples were tested, and then, they underwent micro-scale analysis. The results showed that, with the continuous increase in EPS doping and dynamic stress, the trend of the growth of the dynamic strain of the specimens increased. At the same time, with the increase in the dynamic strain, the dynamic elastic modulus decreased, and the trend increased with increasing doping of the soil with EPS particles. A comparison of the improvement effect coefficient of the soil samples showed that the most suitable EPS doping volume was 5%. Different dosages of sisal fibre were added to the most suitable EPS-modified lightweight soil, and the dynamic elastic modulus first increased and then decreased with increasing sisal dosage. In addition, the damping ratio first increased and then decreased. The best dynamic performance of the soil was obtained when the dosage of sisal was 1.2%. Nuclear magnetic resonance and electron microscope scanning tests verified that, when the sisal doping was 1.2%, the soil particles had the largest compactness, the best interparticle bonding and the best improvement effect.