The research focuses on ancient landslides in south-west China's mountainous areas, which are often overlooked due to their blending with the natural terrain. A case study from a bridge slope in Yunnan Province is used to investigate the reactivation of these landslides. This study explores the reactivation mechanisms of ancient landslides triggered by construction excavation disturbances combined with rainfall infiltration, a topic rarely examined in mountainous plateau regions. Through extensive monitoring of both surface and deep displacements during highway construction, the study reveals the dynamics of landslide resurgence. It identifies engineering excavations and pre-existing ancient sliding zones as the primary triggers for slope instability, with rainfall infiltration exacerbating the issue and causing a complex, layered sliding pattern. Numerical simulations are employed to recreate the landslide's resurgence, forecast its future behaviour and guide reinforcement strategies. This research underscores the significance of correctly identifying ancient landslides and implementing appropriate mitigation measures in construction projects, offering valuable insights for hazard management in similar geological settings.

The initial terrain of a slope has a significant impact on the stability and stress state during excavation. In this study, the theory of elastic stress solutions under concentrated loads at the top of a wedge-shaped body was employed to develop a method for calculating the slope stress field and stability, considering terrain effects during excavation. The rationality of this method was validated by comparing the changes in the safety factor, stress of the sliding surface, and position of the sliding surface using the limit equilibrium method (LEM) and finite element method (FEM). The research findings indicated the following: (1) A sliding surface search method was proposed, leading to the development of a slope unloading stress analysis method (USAM) considering the influence of terrain. This method allows for the rapid and straightforward determination of the stress field and safety factor of the excavated slope simultaneously. (2) When the USAM was applied to analyze slopes with small heights, the safety factor tended to be slightly larger. This phenomenon can be attributed to the assumption made in the elastic stress solution theory for wedge tops subjected to concentrated loads. However, this assumption does not significantly affect the stability analysis of high slopes. (3) The calculated sliding surface stresses and potential sliding surface positions were close to those derived using the strength reduction method. This study introduces a new perspective for slope stability analyses and stress field solutions that consider terrain effects.

In constructing rapid rock identification models for measurement while drilling (MWD) via neural network methods, collecting actual drilling data to train the model is extremely time-consuming and labor-intensive. This requires extensive drilling experiments in various rock types, resulting in limited neural network training data for rock identification that covers a limited range of rock types. To suitably address this issue, a dynamic numerical simulation model for rock drilling is established that generates extensive drilling data. The input parameters for the simulations include torque, drill bit rotation speed, and drilling speed. A neural network model is then developed for rock classification using large datasets from dynamic numerical simulations, specifically those of granite, limestone, and sandstone. Building upon this model, transfer learning is appropriately applied to store the knowledge obtained in the rock identification based on the neural network model. Further training through transfer learning is conducted with smaller datasets obtained during actual drilling, making the model suitable for practical rock identification and prediction in the drilling processes. The neural network rock classification model, incorporating dynamic numerical simulation and transfer learning, achieves a prediction accuracy of 99.36% for granite, 99.53% for sandstone, and 99.82% for limestone. This reveals an enhancement in prediction accuracy of up to 22.94% compared to the models without transfer learning.

The in situ stress conditions of reservoirs are the fundamental parameters for determining the arrangements of horizontal boreholes and assessing borehole stability, especially for the exploration and exploitation of unconventional oil and gas. The borehole wall stress relief method (BWSRM) is a new technique that can directly measure three-dimensional (3D) stress without any assumptions regarding the stress field. In deep vertical borehole situations, a new experiment is proposed to prevent electronic components from becoming damp while simultaneously maintaining borehole stability. The effect of drilling fluid pressure on the strain measurement of the stress relief processes is studied. The finite-element model (FEM) simulates the stress relief process and verifies the theoretical solutions under different testing depths. The results show that complete stress relief is impossible under deep vertical borehole conditions, and the wall drilling process changes the stress conditions of the measured points from modified plane strain to triaxial compression. Therefore, the data measured by the strain gauges cannot be directly imported into the original relationships between the measured strains and far-field stress. The comparisons between the original theoretical solutions and FEM results indicate that if the confining pressure is ignored, then the maximum error between the measured and real in situ stress components is over 35%. After correcting the estimated strain data using the proposed methods, the stress tensors obtained from theoretical equations are consistent with the natural stress tensors. (c) 2024 AmericanSociety of Civil Engineers.

Relationships between drilling parameters and the uniaxial compressive strength (UCS) of rocks are typically established through measurement while drilling (MWD) by analyzing either drilling speed or specific energy. This study enhances the commonly utilized specific energy formula by considering the frictional dissipation energy of the drill bit, along with the initial thrust and torque exerted by the drilling machines. A novel specific energy index, eta p, optimized for rotary drilling applications, was introduced. The modified expressions significantly mitigate the impact of variations in drilling parameters on the specific energy. Employing the concept of a minimum specific energy coefficient, a model was developed that directly relates drilling parameters to the UCS of rocks. An iterative solution method for determining the minimum specific energy coefficient was provided. Extensive MWD tests on intact granite samples, conducted on a specially developed indoor drilling test platform, facilitated the calibration of the minimum specific energy coefficient. The model's efficacy in UCS estimation was further validated through additional MWD tests on sandstone and limestone. For sandstone, the model's estimated UCS showed a relative error (RE) ranging from 0.62% to 21.22%, a mean relative error of 11.7%, and a maximum absolute error of 9.75 MPa. Limestone tests revealed an RE range of 1.99%-12.86%, with absolute errors between 2.53 and 16.4 MPa. The UCSs of sandstone and limestone were estimated to lie between 39.65 and 55.71 MPa and 113.29 and 143.90 MPa, respectively, demonstrating close alignment with the results of uniaxial compressive strength tests and confirming the model's accuracy and reliability for UCS prediction using MWD data.

In situ stress is an essential parameter that directly affects all engineering construction and scientific research in deep rock masses. The shapes of deep borehole are often highly irregular, so that the traditional in situ stress measurement methods based on the assumption of circular or cylindrical boreholes are no longer applicable. We propose a stress relief correction method considering irregular borehole shape using the complex function method of elasticity. The conformal mapping function is introduced to project the irregular shape into a unit circle and the relationship between the strains at the borehole wall and the far-field in situ stress components are solved by the Cauchy integral methods. The results show the following: (1) The stress results from the stress relief correction method are consistent with the theoretical solutions and numerical simulation results for circular and square boreholes. (2) The irregular borehole shape significantly changes the distribution of stress magnitude and the direction of strain measurement on the borehole wall. The stress relief correction method considering irregular borehole shapes provides an essential theoretical basis for deep rock mass engineering construction and deep oil and gas field exploration.

Landslides often occur along motorways in earthquake-prone areas, leading to casualties and the loss of property. Most previous studies have applied the simplified Newmark method to assess landslide susceptibility at a regional scale, ignoring the characteristics of local ground motions. In this study, we investigated permanent displacement characteristics of three potential landslide areas along the Dayong Expressway using the rigorous Newmark method that considers the frequency and energy characteristics of historical seismic waves. First, the frequency characteristics of historical earthquakes in the study areas were analysed using the fast Fourier transform method and were adopted as input ground motions in calculating the Newmark displacement. Next, the critical accelerations of the three study areas were computed. Parameters such as the elevation, soil layer thickness and soil strength that are required for critical acceleration calculations were obtained using high-precision ( c. 3 cm) unmanned aerial vehicle mapping technology, drilling operations and laboratory tests. Finally, the Newmark displacement was calculated and the landslide susceptibility of the study areas was evaluated. The results showed that the predominant frequency of historical seismic waves in the study areas was 0.38–3.36 Hz, indicating low-frequency characteristics. The results also indicated that the frequency and energy characteristics of the seismic ground motions significantly influenced the Newmark displacement. The maximum Newmark displacement under different waveforms at Damieju ranged from 2 to 18 cm. Under the most dangerous conditions, all three areas showed a potential for landslides. The maximum Newmark displacement positively correlated with the energy of the predominant frequency. The large-energy and low-frequency characteristics of the seismic wave correspond to a large displacement. The simplified Newmark method when used in regional landslide susceptibility analysis did not reflect this effect and may be unsuitable to determine the size of landslides.

It is generally believed that core discing is a rock failure phenomenon under high in-situ stress, and high stress is closely related to the characteristics of core discing. The core drilling tests of intact granite were conducted on the laboratory servo-controlled drilling test platform. It was observed that the granite core showed discing phenomenon at a high drilling rate (>15 mm/min) under no confining pressure (0 MPA). The fluctuation of the drilling parameter was consistent with the core discing section along the core. The failure mode of the core discs was determined by morphology and surface fractal dimension characteristics. Numerical simulation models considering the interaction between the drill bit and the rock were established using ANSYS software. Based on core drilling tests, failure morphology analysis of the core discs, and numerical simulation, the mechanism of granite core discing under low confining pressure is as follows: Tensile failure is caused by the stress concentration of the bit at the core root. The drilling rate is the critical factor affecting core discing.

Measurement while drilling (MWD) data reflect the drilling rig–rock mass interaction; they are crucial for accurately classifying the rock mass ahead of the tunnel face. Although machine-learning methods can learn the relationship between MWD data and rock mechanics parameters to support rock classification, most current models do not consider the impact of the continuous drilling-sequence process, thereby leading to rock-classification errors, while small and unbalanced field datasets result in poor model performance. We propose a novel deep neural network model based on Bi-directional Long Short-Term Memory (BILSTM) to extract information-related sequences in MWD data and improve the accuracy of the rock-mass classification. Two optimization modules were designed to improve the model’s generalization performance. Stratified K-fold cross-validation was used for model optimization in small and unbalanced datasets. Model validation is based on the MWD dataset of a highway tunnel in Yunnan, China. Multiple metrics show that the prediction ability of the network is significantly better than those of a multilayer perceptron (MLP) and a support-vector machine (SVM), while the model exhibits an improved generalization performance. The accuracy of the network can reach 90%, which is 13% and 15% higher than the MLP and SVM, respectively.

Landslides often occur along expressways in earthquake-prone areas, leading to casualties and property loss. Most previous studies applied the simplified Newmark method to assess landslide susceptibility at a regional scale, ignoring the characteristics of local ground motions. In this study, we investigated permanent displacement characteristics of three potential landslide areas along the Dayong expressway using the rigorous Newmark method, considering the frequency and energy characteristics of the historical seismic waves. First, we analyzed the frequency characteristics of historical earthquakes in the study areas using the fast Fourier transform method and adopted them as input ground motions in calculating the Newmark displacement. Next, we computed the critical accelerations of the three study areas. Parameters such as the elevation, soil layer thickness, and soil strength required for critical acceleration calculations were obtained using high-precision (approximately 3 cm) unmanned aerial vehicle mapping technology, drilling operations, and laboratory tests. Finally, the Newmark displacement was calculated, and landslide susceptibility of the study areas was evaluated. The results showed that the predominant frequency of historical seismic waves in the study areas was 0.38–3.36 Hz, indicating low-frequency characteristics. The results also indicated that the frequency and energy characteristics of the seismic ground motions significantly influenced the Newmark displacement. The maximum Newmark displacement under different waveforms at Damieju ranged from 2 to 18 cm. Under the most dangerous conditions, all three areas showed potential for landslides. The maximum Newmark displacement positively correlated with the energy of the predominant frequency. Large energy and low frequency characteristics of seismic wave corresponds to a large displacement. The simplified Newmark method in regional landslide susceptibility analysis did not reflect this effect and may be unsuitable to determine the size of landslides.

The rock properties are related to the stress environment and dynamic disturbance during construction, and the testing-while-drilling-technique was used for evaluation of rock properties. However, the related research ignored the influences of stress environment and drilling parameters. In this study, triaxial compression tests and laboratory drilling tests under different confining stresses and drilling parameters were conducted for intact granite, and the numerical changes of drilling parameters were recorded. Then the static elastic energy and drilling specific energy (dynamic energy) of rock were calculated by using linear energy storage theory and rock breaking energy theory, respectively. According to the characteristics of energy variation, an energy analysis method based on drilling process was proposed, and the sum of static elastic energy and dynamic elastic energy was defined as the total energy. The results showed that: 1) the static elastic energy increased with the increase of confining stress, while the drilling specific energy was opposite. 2) For the same rock, the total energy was constant under the same drilling parameters. 3) The influence of drilling parameters on total energy was quantified by dynamic load influence factor. Finally, the potential application of energy analysis method in stress estimation was discussed through drilling tests.

论文《"矢量和法"抗滑稳定计算模型的力学概念错误》[1] (以下简称《质疑》)中,质疑矢量和法计算模型的力学概念问题,认为矢量和法计算模型力学概念错误.作为参与矢量和法研究的研究者,笔者对《质疑》做以下回应.

Completely decomposed migmatitic granite (CDMG) is a kind of rock with special genesis, but there is little research on its mechanical properties and microstructure. In order to explore the relationship between macroscopic strength characteristics and microstructure of Lincang CDMG, triaxial tests and scanning electron microscopy tests were carried out on samples with different moisture contents, and the microstructure parameters that characterized the size, morphology and orientation of particles and pores were extracted and calculated. By investigating these microstructure parameters, the micro mechanism controlling the macroscopic strength characteristics of CDMG is revealed. The results show that with the increase of moisture content, the stress-strain curve of the sample exhibits a dissimilar hardening effect, the shear strength deteriorates significantly, the internal friction angle decreases linearly, and the cohesion fluctuates up and down. Under the condition of low moisture content, the samples are mainly characterized by micro and small pores, and the particle morphology is mostly angular and sub-angular strip with certain orientation. With the increase of moisture content, the pore content shows an upward trend, forming evenly distributed honeycomb medium and large pores, which are easier to be compressed under axial load. The shape of particles develops to be round, and the overall distribution is disorderly and poorly oriented. Comprehensive analysis of the above results shows that the mechanical properties of CDMG are essentially the result of the interaction between microscopic particles and pore structure. The increase of moisture content weakens the friction between coarse particles, resulting in uneven expansion of clay particles, which leads to pore connection and coarsening and damage of filling structure at the micro level, and then shows mechanical properties reduction at the macro level. The research results provide useful reference for the cognition of mechanical properties and microstructure damage evolution of CDMG.

Migmatitic granite is the product of mixed lithification and granitization, and completely decomposed migmatitic granite (CDMG) was formed after weathering. The engineering properties of CDMG are complex, and its engineering properties are complex after weathering, and water content has a great influence on the properties of (CDMG). Due to its loose structure and strong heterogeneity, it is difficult to determine its strength characteristics by conventional test methods. In the paper triaxial and micro-CT test were conducted to study the relationship between shear strength and microstructure of CDMG under different water content. The results show that with the increase of water content from 6

The phenomenon of core discing has always been considered as a unique sign of high geostress area. With the in-depth study of the discing mechanism, there are various indications that the high geostress is not the main controlling factor of the core discing. Based on the geostress classification standard and engineering cases data, the stress level of complete granite prone to discing is determined in this paper. On this basis, laboratory drilling tests with different drilling speeds under high and low stress conditions are designed. The results show that high stress is not the key factor for core discing. When the drilling speed is fast, even if the confining stress is 0, core discing will occur. When the drilling speed is slow, the core can be taken completely even at high stress levels. Drilling parameters fluctuate with discing, and its peaks correspond to the core fracture location.

由于地形条件限制,有些高速公路边坡无法展开深入勘察,地层和岩体性质掌握不清,会影响到边坡设计,严重者引起滑坡,损失巨大.随钻测试是近年来发展的一项原位测试技术,通过钻孔过程中钻进参数的采集分析,获取工程场地地层情况,评价岩体质量.以某在建高速公路高边坡为例,采用 自主研发的随钻测试设备,采集了锚索孔钻孔过程中的钻机钻进参数,通过钻进参数、岩屑特征和临近地段勘察资料的综合分析,识别了边坡的地层情况.结果发现,原勘察资料中认为是中风化灰岩的地层,实际上是崩塌堆积形成的灰岩孤石夹碎石土,整体强度远低于设计值.根据随钻测试的地层识别结果进行了边坡灾后优化设计,边坡变形监测结果验证了优化设计中加固措施的有效性.本文的随钻测试技术和分析方法简单易用,值得在勘察资料不足的边坡工程中推广应用.

The conventional geological prediction method of advanced drilling usually takes the change rate of one specific drilling parameter as the main basis for stratum identification. The rock breaking of drill bit is a complicated mechanical process. Stratum identification with single drilling parameter results in great uncertainty. Thus the combined effect of multiple parameters in drilling process should be considered. Firstly, the advanced drilling data were preprocessed by SPSS, including standardization, frequency distribution analysis and sensitivity analysis, to select the key drilling parameters that are sensitive to stratum changes. Secondly, based on the principles of energy conservation, binary disordered logistic regression analysis and multi-parameter variability analysis, three comprehensive identification indices including rock breaking energy, logistic regression probability and stratum hardness were established respectively. Finally, the stratum identification model was established by probability classification method based on Bayesian principle, the model parameters were determined by ROC analysis method, and the stratum identification based on multiple drilling parameters and probability classification method was realized. Taking the tunnel project with complex geological conditions as an example, the application of the proposed stratum identification method is introduced. The results show that three comprehensive indices perform well in cross-hole stratum identification, and the identification accuracy exceeds 80%. The rock breaking energy and the logistic regression probability are suitable for the cross-hole stratum identification with short distance, and the average identification accuracies are 86.3% and 84.1%, respectively. The logistic regression probability index has strong identification capability for the weak interlayer, and the identification accuracy reaches 94.2%. The stratum hardness index is suitable for the cross-hole stratum identification with long distance, and the maximum identification accuracy of limestone is 93.2%.

In earthquake-prone areas, special attention should be paid to the study of the seismic stability of rock slope. Particularly, it becomes much more complicated for the rock slopes with weak structural surfaces. In this study, numerical simulation and the shaking table test are carried out to analyze the influence of seismic excitation and structural surface in different directions on dynamic response of rock slope. Huaping slope with bedding structural surfaces and Lijiang slope with discontinuous structural surfaces besides Jinsha River in Yunnan Province are taken as research objects. The results of numerical simulation and the model test both show that discontinuous structure surface has influence on the propagation characteristics of seismic wavefield. For Huaping slope, the seismic wavefield responses repeatedly between the bedding structural surface and slope surface lead to the increase of the amplification effect. The maximum value of seismic acceleration appears on the empty surface where terrain changes. Horizontal motion plays a leading role in slope failure, and the amplification coefficient of horizontal seismic acceleration is about twice that of vertical seismic acceleration. The failure mode is integral sliding along the bedding structural surface. For Lijiang slope, seismic acceleration field affected by complex structural surface is superimposed repeatedly in local area. The maximum value of seismic acceleration appears in the local area near slope surface. And the dynamic response of slope is controlled by vertical and horizontal motion together. Under the seismic excitation with an intense of 0.336 g in X direction and Z direction, the amplification coefficients of seismic acceleration of Lijiang slope are 3.23 and 3.18, respectively. The vertical motion leads to the cracking of the weak structural surface. Then, Lijiang slope shows the toppling failure mode under the action of horizontal motion.

Reliable geology prediction is of great importance in ensuring the stability and safety of tunnels and other underground engineering projects. This paper presents basic neural network and deep neural network models using a genetic algorithm (GA) to predict geological conditions for tunneling. Batch normalization and GA optimization approaches are employed in the deep neural network. A case study of the Jiudingshan Tunnel on the Chuxiong–Dali Highway in Yunnan, China, shows that the neural network method can predict geological conditions well, especially for rock types with voluminous data, for which predictive accuracy exceeds 90%. These results suggest that an appropriately trained neural network can reliably and accurately predict the geological conditions behind the tunnel face. The area under the curve (AUC) and confusion matrix evaluations show that the accuracy performance of the deep neural network exceeds that of the basic neural network. The feature importance of each drilling parameter was also analyzed; the results indicate that a neural network model for geology prediction can achieve predictive accuracy with few drilling parameters. The neural network geology prediction method provides reliable results for dynamic tunnel design.

地应力参数的获取对于页岩气的勘查评估以及开发工作十分重要.其中,水平差应力系数是决定地层可采性的基础参数之一.为了更为准确地确定地应力参数,克服传统应力解除法测试深度有限、解除作业时间较长、测试成功率较低的问题,提出了一种基于高精度位移测量的水平差应力系数计算方法,并采用有限元方法对公式进行验证.考虑钻井液液柱压力对维持井壁稳定性的重要作用,进一步修正公式,使其能适用于深孔有压环境下,并分析了主要误差来源,给出控制误差的方法.研究得出:通过比较理论反算结果与数值计算结果,表明推导出的公式的正确性;有限元计算表明,在岩芯直径为30 mm的条件下,环切深度达到48 mm即能达到完全应力解除的目的,与传统取芯方法相比大大减少;在同一平面布置间隔120°三处测试点,能够满足测试需要;该方法的误差来源主要包括位移测试精度、岩体不连续面存在以及岩体变形参数、钻孔形态参数精度等,并给出了相应的控制方法.这种新方法不受孔深限制,具有测试时间短、测试成功率高的特点,对于页岩气的勘查以及开发具有重要的意义.