Experimental Research on the Load/Unload Response Ratio (LURR) Theory

Implementing acoustic emission experiments with large rock samples, LURR (Load/Unload Response Ratio) theory was studied. The loading conditions in the experiments were designed to simulate the complicated loading process of underground rocks. The damages emerging inside the rock samples were recorded by the acoustic emission technique during the loading process. The experimental results were consistent with prediction by LURR theory. Integrating the changing processes of LURR value Y and the location process of acoustic emission events showed agreement between the variation of LURR value Y and the damage evolution inside the rocks. Furthermore, the high value of Y emerged before the complete breakdown of materials. Therefore, the damage evolution of rock specimen can be quantitatively analyzed with LURR theory, thus the failure of the rock materials and the earthquake occurrence may be predicted. The experimental results gave a further verification of LURR theory.

The tempo-spatial evolution characteristics of the load/unload response ratio before strong earthquakes in California of America and its predicting implications

In this paper, the tempo-spatial evolution characteristics of the load/unload response ratio (namely LURR or Y value) before strong earthquakes with magnitude over 6 during 1976~1994 in California of America are studied in detail. The results show that there appear some high-Y regions cohering with the regional tectonic trend in a great area 3~4 years before strong earthquakes and these high-Y regions migrate from the periphery to the epicenter region at a speed of tens of kilometers per year. The load/unload response ratio (LURR) anomalies near the epicenter region characterizes a type of (ascend ? descend( and appear and increase steeply until one year or less before most earthquakes. (Positive( earthquakes form usually a concentration area; in and near which the main shock occurs. We have analyzed the different and same characters of earthquakes between California of American and the Chinese mainland. Basing on these results, we discuss the approach and method how to predict and estimate the three parameters (place, time and magnitude) of a strong earthquake in California of American by applying the characteristics of the LURR.

Physical meaning and prediction efficiency of the load/unload response ratio of rocks in strain-weakening phase before failure

Rock experiment results indicate that the load/unload response ratio (LURR) of rocks expressed via strain energy may have singular or negative value after the stress in the rock reaches its maximum before rock failure or when the rock goes into the strain-weakening phase. The universality of this phenomenon is discussed. Expressed via strain or strain energy and the travel time of P wave, the variation form of the reciprocal of LURR during the process of rock failure preparation is derived. The results show that after a sharp decrease the reciprocal of LURR reaches its minimum when the main fracture of the rock is about to appear. This feature can be taken as an indication that the rock main fracture is impending.

The Experimental Simulation of Rocks on Load/Unload Response Ratio for Earthquake Prediction

The load/unload experiments on rock failure under pressure have been carried out in Material Test System (MTS) in the Laboratory for Non-linear Mechanics of Continuous Media (LNM), Institute of Mechanics, Chinese Academy of Sciences, and load/unload response ratio (LURR) values with strain as response (i.e. inverse elastic constant as response rate) have been obtained. The experimental results are in accordance with theoretical results and those in real earthquakes: LURR rises just before rock failure. So LURR can be used as the precursor of rock failure and earthquake prediction.

Investigation on the Load/Unload Response Ratio With Coda Q-1 as Response

The load/unload response ratio YQ with the geophysical parameter coda Q-1 of the crust as response is denned in this study.The variation in YQ-1 before and after the Northridge earthquake of January 17,1994(California)has been investigated by using the data of coda Q-1 with frequencies of 1.5,3.0,6.0,12.0,and 24.0 Hz in the Southern California from 1987 to 1994.It can be found that YQ-1 for coda waves with all frequencies,the frequency of 12.0 Hz excluded,ascended to a certain extent prior to the occurrence of the rnainshock and returned to normality after the main shock.

Application of the Load/Unload Response Ratio Theory to Predictions of Moderate Earthquakes (7.0>M≥6.0)

The variation in load/unload response ratio before some moderate earthquakes is analyzed based on the theory of the load/unload response ratio.The results show that the load-unload response ratio increases noticeably before moderate earthquakes,and there are three kinds of patterns in which the load/unload response ratio varies and the duration of noticeable increase in load/unload response ratio ranges from half a year to two years.

Variation of the Load/Unload Response Ratio Before the Main Shocks of the Reservoir-Induced Earthquakes

In this paper, the theory of the load/unload response ratio is applied to the prediction of the reservoir-induced earthquakes, and variation of the load/unload response ratio Y preceding the occurrence of main shocks of the reservoir-induced earthquakes in Xinfengjiang, Foziling, Danjiangkou, and Shenwo. The results show that the load/unload response ratio Y rises evidently prior to the main shocks.

The spatial temporal evolution characteristics of the load／unload response ratio（LURR） and its implications for predicting the three elements of earthquakes

The spatial temPOral evolution characteristics of the load/unload response ratio (Y) before strong earthquakes is studied in this paper. The results show that the regions of high value of Y migrate and converge to the impending earthquake epicenter from different directions before the occurrence of the event. Basing on this discovery, it is proposed that the method can be used to predict the three elements of an earthquake. It was applied to predict that an earthquake would occur in the western part of Yunnan Province, southwestern China. The three elements (time, space and magnitude) of the Menglian earthquake with Ms7.3 which occurred on July 12, 1995 in Yunnan Province tallied with our prediction.

Short-term and imminent anomalies of earthquake of load and unload response ratio of the well level to earth tides

In this paper, through the nonlinear response of rock strain and stress, we have analized the physical mechanism of loading and unloading response ratio of the well level to the earth tides,the respouse of an aquifer of confined well to bulk strain tide and showed two methods of the calculation of loading and unloading response ratio of the well level to the earth tides. We took the example of the Yu 01 well, which is near the epicenter of Heze M S 5.9 earthquake, calculated the response rate and loading and unloading response ratio of two kinds of the earth tides of it. The response rate and response ratio before the earthquake had the variation of increase.

The Random Distribution of the Loading and Unloading Response Ratio Under the Assumptions of Poisson Models

This paper discussed the random distribution of the loading and unloading response ratio（LURR） of different definitions（Y1～Y5）using the assumptions that the earthquakes occurfollowing the Poisson process and their magnitudes obey the Gutenberg-Richter law.Theresults show that Y1～Y5 are quite stable or concentrated when the expected number of eventsin the calculation time window is relatively large（】40）;but when this occurrence ratebecomes very small,Y2～Y5 become quite variable or unstable.That is to say,a high value ofthe LURR can be produced not only from seismicity before a large earthquake,but also from arandom sequence of earthquakes that obeys a Poisson process when the expected number ofevents in the window is too small.To check the influence of randomness in the catalogue tothe LURR,the random distribution of the LURR under Poisson models has been calculated bysimulation.90%,95% and 99% confidence ranges of Y1 and Y3 are given in this paper,which is helpful to quantify the random

The Natural Probability Distribution of Load and Unload Response Ratio

In this paper,the Gutenberg-Richter model is used to generate seismic events.The events that satisfy the random distribution are also generated.With those events,the natural probability distribution of Load and Unload Response Ratio(LURR),which measures quantitatively the degree of instability of a nonlinear system,is discussed.The study is based on stress energy release,which is chosen as the response of nonlinear system F3.The comparative results from the observation catalogue and generating data are also studied.It is revealed that the natural probability of LURR is mostly stable when the sample number is sufficient.The lower the natural probability of LURR,the more the precursory is information it may contain.The influence of Y3 resulting from the sample number and the magnitude range of events is also discussed.

Local Anomalies of the Load-Unload Response of the Geomagnetic Field to Solar Wind and Earthquakes in Southwest China

Many earthquakes occurred during the period 1994 -1996 in Sichuan and Yunnan Provinces, Southwest China. Taking the process of the initial main phase recovery phase of the magnetic storm as the process of load-unload response of the geomagnetic field to the solar wind, we have estimated and analyzed the distribution in time and space of the load-unload response ratio P(z) of the storm time disturbance daily variation of the vertical component Z of the geomagnetic field at ten stations in Southwest China. We found that the area with high ratio P(z) was just the area where moderately strong earthquakes would occur from 44 days to 15 months later. The relationship between the high ratio P(z) and weather disasters in both seismic and non-seismic areas is discussed briefly.

Evolution of mechanical parameters of Shuangjiangkou granite under different loading cycles and stress paths

Surrounding rocks at different locations are generally subjected to different stress paths during the process of deep hard rock excavation.In this study,to reveal the mechanical parameters of deep surrounding rock under different stress paths,a new cyclic loading and unloading test method for controlled true triaxial loading and unloading and principal stress direction interchange was proposed,and the evolution of mechanical parameters of Shuangjiangkou granite under different stress paths was studied,including the deformation modulus,elastic deformation increment ratios,fracture degree,cohesion and internal friction angle.Additionally,stress path coefficient was defined to characterize different stress paths,and the functional relationships among the stress path coefficient,rock fracture degree difference coefficient,cohesion and internal friction angle were obtained.The results show that during the true triaxial cyclic loading and unloading process,the deformation modulus and cohesion gradually decrease,while the internal friction angle gradually increases with increasing equivalent crack strain.The stress path coefficient is exponentially related to the rock fracture degree difference coefficient.As the stress path coefficient increases,the degrees of cohesion weakening and internal friction angle strengthening decrease linearly.During cyclic loading and unloading under true triaxial principal stress direction interchange,the direction of crack development changes,and the deformation modulus increases,while the cohesion and internal friction angle decrease slightly,indicating that the principal stress direction interchange has a strengthening effect on the surrounding rocks.Finally,the influences of the principal stress interchange direction on the stabilities of deep engineering excavation projects are discussed.

Feasibility study on buoyancy-weight ratios of a submerged floating tunnel prototype subjected to hydrodynamic loads

The research progress of a novel traffic solution,a submerged floating tunnel（SFT）,is reviewed in terms of a study approach and loading scenario.Among existing publications,the buoyancy-weight ratio（BWR） is usually predefined.However,BWR is a critical structural parameter that tremendously affects the dynamic behaviour of not only the tunnel tube itself but also the cable system.In the context of a SFT prototype（SFTP） project in Qiandao Lake（Zhejiang Province,China）,the importance of BWR is illustrated by finite element analysis and subsequently,an optimized BWR is proposed within a reasonable range in the present study.In the numerical model,structural damping is identified to be of importance.Rayleigh damping and the corresponding Rayleigh coefficients are attained through a sensitivity study,which shows that the adopted damping ratios are fairly suitable for SFTP.Lastly,the human sense of security is considered by quantifying the comfort index,which helps further optimize BWR in the SFTP structural parameter design.

APRI as a predictor of early viral response in chronic hepatitis C patients

AIM:To evaluate the aspartate aminotransferase(AST) to platelet ratio index(APRI) as a predictive factor of early viral response in chronic hepatitis C naive patients.METHODS:We performed an ambispective case-control study.We enrolled chronic hepatitis C naive patients who were evaluated to start therapy with PEGylated interferon α-2b(1.5 μg/kg per week) and ribavirin(>75 kg:1200mg and <75kg:1000mg).Patients were allocated into two groups,group 1:Hepatitis C patients with early viral response(EVR),group 2:Patients without EVR.Odds ratio(OR) and 95% confi dence interval(CI) were calculated to assess the relationship between each risk factor and the EVR in both groups.RESULTS:During the study,80 patients were analyzed,45 retrospectively and 35 prospectively.The mean ± SD age of our subjects was 42.9 ± 12 years;weight 70 kg(±11.19),AST 64.6 IU/mL(±48.74),alanine aminotransferase(ALT) 76.3 IU/mL(±63.08) and platelets 209000 mill/mm3(±84 429).Fifty-five(68.8%) were genotype 1 and 25(31.3%) were genotype 2 or 3;the mean hepatitis C virus RNA viral load was 2 269 061 IU/mL(±7220266).In the univariate analysis,APRI was not associated with EVR [OR 0.61(95% CI 0.229-1.655,P=0.33)],and the absence of EVR was only associated with genotype 1 [OR 0.28(95% CI 0.08-0.94,P=0.034)].After adjustment in a logistic regression model,genotype 1 remains signifi cant.CONCLUSION:APRI was not a predictor of EVR in chronic hepatitis C;Genotype 1 was the only predictive factor associated with the absence of EVR in our patients.

三轴分级循环加卸载下爆破损伤顶板砂岩能量耗散试验研究

为探究不同围压环境爆破荷载损伤砂岩在循环加卸载作用下能量耗散演化规律,利用三轴试验加载装置系统对三种不同损伤度的砂岩试件开展不同围压下的分级循环加卸载试验,并结合电子数码显微镜获取不同损伤度试件细观结构,分析爆破荷载损伤、围压及加载级数对试件能量耗散及破裂破碎形态的影响规律。结果表明:(1)爆破荷载作用会对岩体造成损伤,单轴压缩荷载下振动损伤、爆破损伤试件峰值强度降幅分别为5.53%、18.87%,单轴分级循环加卸载作用对未损伤、振动损伤试件产生劣化,对爆破损伤试件产生强化作用;(2)爆源近端岩体损伤程度较高,在外荷载作用下率先发生破坏,围压的存在显著降低试件的破裂破碎程度,试件呈剪切、拉伸及压碎破坏多种模式共存;(3)循环加卸载过程中第1次循环加载试件所获取总能量及塑性变形能最大,循环次数的增加使试件塑性变形能及耗散能整体均呈现减小趋势,围压及循环加载级数的增大使试件在循环加载过程中各能量均随之增加;(4)分级循环加卸载过程中Ⅱ级循环加卸载试件耗能比要低于Ⅰ级与Ⅲ级,爆破损伤、振动损伤及未损伤试件在Ⅰ级、Ⅱ级、Ⅲ级循环加卸载过程中耗能比均值分别为15.73%、12.47%、13.95%,13.49%、12.44%、13.46%,12.07%、8.69%、11.56%,爆破荷载损伤改变岩体内部结构使得试件在循环加卸载作用下耗能占比更加显著。

考虑富氧燃烧碳捕集技术和源荷双侧响应的综合能源系统优化调度

为降低燃气轮机的碳排放水平和提高灵活性,提出了计及富氧燃烧碳捕集技术和源荷双侧响应的综合能源系统低碳经济优化策略。首先,研究了富氧燃烧技术的运行原理及其能流特性,并构建空分制氧设备和碳捕集设备的耦合模型;其次,引入可调的热电比作为供给侧响应策略,需求侧对于电力、热能以及气负荷的特性进行综合权衡,借助能源价格的引导,并考虑其相互之间的可替代属性形成需求侧响应机制;最后,通过计及气负荷碳排放的阶梯式碳交易约束碳排放,以系统运行成本为目标优化各时段机组出力。设置多场景进行仿真分析,结果表明富氧燃烧碳捕集技术能够有效减少系统的碳排放量,源荷双侧响应能够灵活调节供给侧与需求侧的供能关系,并有效减少系统运行成本。

地磁异常识别技术在松原5.7级地震前的应用研究

运用地磁异常识别技术对2018年5月28日松原5.7级地震前的地磁异常展开研究。采用加卸载响应比法、逐日比法、日变化空间相关法、异常叠加法对吉林省三岗台、通化台及东北地区邻近的大连台、营口台、朝阳台、铁岭台等台站,运用松原5.7级地震前18个月内的地磁预处理分钟值数据进行计算分析和异常判定识别。研究结果表明:在加卸载响应比法、逐日比法和日变化空间相关法的基础上,运用异常叠加法提取的地磁异常,其预测的位置与真实值更加接近,预测结果对省内地震具有重要的指示意义。

基于LURR的前震分析方法及其在川滇地区的应用

加卸载响应比(Load-Unload Response Ratio,LURR)是基于岩石介质本构关系动态变化提出的一种中短期地震预测方法,然而,在实践应用中存在构造剪应力方向难以确定的问题.本文以前震为研究对象,发展了一种确定构造剪切应力方向的新思路.当4级以上地震发生后,通过沿该地震滑动方向计算库仑破坏应力(CFS)的变化,判断其固体潮加卸载状态,探测后续强震发生的可能性.以川滇地区(20°N—35°N,96°E—106°E)为研究区域,分析2000年以来所有6级以上地震的4级以上前震的加卸载状态发现,大部分4级以上前震发生在加载阶段.进一步分析近10年来所有4级以上地震的加卸载状态发现,非前震则更易发生在卸载阶段.结合概率增益分析可知,(1)若原震区连续发生至少2个4级以上地震,且均位于固体潮加载过程,后续发生强震的可能性较大;(2)当地震位于卸载过程,原震区发生更强地震的可能性要低于平时的背景地震活动水平.此外,对2022年11月以来的4级以上地震加卸载状态分析推测,川东南、滇南、滇西北地区应力积累水平较高,需要重点关注强震危险性.

利用加卸载响应比探查强震成核过程——以2020年新疆伽师6.4级地震为例

加卸载响应比(LURR)是基于非均匀脆性介质损伤演化提出的一种中短期地震预测方法,以往的研究中多以地震活动为响应量计算LURR,地球物理观测资料应用较少.本文基于地下流体、地壳形变、电磁、岩石地温等观测资料,运用加卸载响应比(LURR)方法研究2020年新疆伽师6.4级地震的孕育过程.震中300 km范围内的20个观测台站中,11个台站数据计算得到的LURR时间序列呈现明显规律性特征.震前数月-数天都出现相对异常高值,并在回落后发生地震,演化过程与使用震中200 km范围内小震活动计算的LURR时间序列一致.不同观测资料所得LURR异常阈值分别为:地下水位1.02、岩石地温1.0002、倾斜仪1.005、水温1.02、氢气1.02、地电阻率1.01、地磁1.02、小震活动1.5.从异常台站的空间分布上看,存在向震中迁移的过程,即随着主震发生时间的临近,检测到异常的台站位置与震中之间的距离越小,且在震中附近呈现加速过程.LURR异常的时空演化可能与岩石介质的亚失稳有关,反映了大震前震源区介质的成核弱化和加速破裂过程.上述演化过程可以通过原始观测曲线中记录的异常数量、空间分布及其随时间的演化加以证实.