This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficie...This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficient(i)and the stratum thickness(H)follows a piecewise linear trend.Specifically,within strata of identical elastic modulus(E),i exhibits a linear correlation with H,while variations in E affect the slope of this correlation.Building upon the non-iterative analytical method(NIAM)for evaluating tunnel excavation responses in composite strata,this study proposes two novel approaches:the crucial point method(CPM)and the standard curve method(SCM).These methods incorporate the elastic modulus into the estimation of i.The values of i obtained via NIAM and refined through CPM and SCM are validated against field data using the parameter K.The results are consistent with existing research findings,thereby confirming the reliability of the proposed methodology.Furthermore,the study investigates the relationship between tunnel depth(h0)and tunnel radius(R),and explores the interactions among the layer number of stratum(n),elastic modulus(E),and layer thickness(H).A reduction coefficient(η)is introduced to improve the model's accuracy.The proposed approach is applied to nine tunnel engineering cases,and comparisons with measured data demonstrate its accuracy and practical applicability.展开更多
Deep excavations in silt strata can lead to large deformation problems,posing risks to both the excavation and adjacent structures.This study combines field monitoring with numerical simulation to investigate the unde...Deep excavations in silt strata can lead to large deformation problems,posing risks to both the excavation and adjacent structures.This study combines field monitoring with numerical simulation to investigate the underlying mechanisms and key aspects associated with large deformation problems induced by deep excavation in silt strata in Shenzhen,China.The monitoring results reveal that,due to the weak property and creep effect of the silt strata,the maximum wall deflection in the first excavated section(Section 1)exceeds its controlled value at more than 93%of measurement points,reaching a peak value of 137.46 mm.Notably,the deformation exhibits prolonged development characteristics,with the diaphragm wall deflections contributing to 39%of the overall deformation magnitude during the construction of the base slab.Subsequently,numerical simulations are carried out to analyze and assess the primary factors influencing excavation-induced deformations,following the observation of large deformations.The simulations indicate that the low strength of the silt soil is a pivotal factor that results in significant deformations.Furthermore,the flexural stiffness of the diaphragm walls exerts a notable influence on the development of deformations.To address these concerns,an optimization study of potential treatment measures was performed during the subsequent excavation of Section 2.The combined treatment approach,which comprises the reinforcement of the silt layer within the excavation and the increase in the thickness of the diaphragm walls,has been demonstrated to offer an economically superior solution for the handling of thick silt strata.This approach has the effect of reducing the lateral wall displacement by 83.1%and the ground settlement by 70.8%,thereby ensuring the safe construction of the deep excavation.展开更多
Coal mining in groundwater-rich coal fields will trigger failure of overlying strata,resulting in the formation of water-conducting fracture zone(WCFZ)and potentially leading to water-inrush accidents.In this study,a ...Coal mining in groundwater-rich coal fields will trigger failure of overlying strata,resulting in the formation of water-conducting fracture zone(WCFZ)and potentially leading to water-inrush accidents.In this study,a reliability model with consideration of spatial variability and uncertainty of strength parameters was proposed to predict the failure behaviour of overlying strata during coal mining in groundwater-rich coalfields.Rock strength parameters,including cohesion,internal friction angle,uniaxial tensile strength,and softening coefficient,are treated as random variables to determine the rock failure uncertainty.The experimental results of these geomechanical parameters at different positions are interpolated by the Kriging interpolation method.Spatially,the interpolated values are arranged as the average value of each random variable to demonstrate their autocorrelation.Furthermore,based on Mohr–Coulomb yield criterion,a performance function is deduced to calculate the failure probabilities of overburden rocks to evaluate the spatial scale of WCFZ.As a typical case,the failure features of adjacent overlying strata of No.7121 mining face in Qidong Coal Mine is analyzed.The results show that the risks of water-inrush are high when the mining face advances to 260–380 m and 1120–1240 m,which aligns with both field monitoring results and borehole observation results.The proposed model holds significant implications for prevention of water-inrush accidents in groundwater-rich coal mines.展开更多
Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogen...Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogeneous strata,with limited research conducted on the upper loose and lower dense strata.Active instability tests are conducted in this study,in concert with the digital image correlation(DIC)technique,to investigate the effects of different water pressure ratios in upper loose and lower dense water-rich strata.The accuracy of these model tests is verified using numerical simulations.The results indicate that as water pressure ratio decreases,there is an increase in both the peak displacement of surface settlement and the seepage path range of water ahead of the excavation face expands.In contrast,decreasing water pressure ratio will break the limit equilibrium state of the strata faster,cause the earth pressure on the cutterhead to change more rapidly,and increase the instability range of the strata.展开更多
煤矿井下复杂施工环境导致超前钻探中钻具响应与岩性映射关系通常难以直接建立,制约岩性识别精度。针对此问题,构建了聚晶金刚石复合片(PDC)钻头-钻杆破岩仿真模型,揭示了不同钻进条件下钻具对复合岩层的响应特征:固定钻速,提升转速会...煤矿井下复杂施工环境导致超前钻探中钻具响应与岩性映射关系通常难以直接建立,制约岩性识别精度。针对此问题,构建了聚晶金刚石复合片(PDC)钻头-钻杆破岩仿真模型,揭示了不同钻进条件下钻具对复合岩层的响应特征:固定钻速,提升转速会使钻头扭矩降低且波动减弱,而钻压波动相对稳定;固定转速,提升钻速会使钻压与扭矩同步升高。钻杆三轴向振动加速度随转速增大而增大,随钻速增大呈先减小后增大趋势。在岩性界面处,上述参数呈现突变特征,表明多参数联合可作为岩性识别特征。基于此,提出了一种融合双向长短期记忆网络(BiLSTM)、注意力机制与KAN(Kolmogorov-Arnold Network)的岩性识别模型——BiLSTM-Att-KAN,以KAN替代BiLSTM模型中多层感知机(MLP)分类器,突破MLP因使用Sigmoid/Rectified Linear Unit(ReLU)等固定激活函数导致的非线性映射局限,可提高复杂岩性识别精度。利用仿真数据和实际数据进行模型测试,结果表明:BiLSTM-Att-KAN在仿真数据集上的识别准确率达91.64%,优于K近邻、随机森林等传统分类模型,提升幅度7.00%~22.08%;在实际训练钻孔数据测试集与独立测试数据上的准确率分别为86.81%和85.28%,验证了模型有效性,可为煤系地层岩性识别提供技术支撑。展开更多
基金support from the National Natural Science Foundation of China(Grant No.52278387).
文摘This study investigates the influence of the elastic modulus(E)of the composite strata on the trough width coefficient(i).It is hypothesized that,in composite strata,the relationship between the trough width coefficient(i)and the stratum thickness(H)follows a piecewise linear trend.Specifically,within strata of identical elastic modulus(E),i exhibits a linear correlation with H,while variations in E affect the slope of this correlation.Building upon the non-iterative analytical method(NIAM)for evaluating tunnel excavation responses in composite strata,this study proposes two novel approaches:the crucial point method(CPM)and the standard curve method(SCM).These methods incorporate the elastic modulus into the estimation of i.The values of i obtained via NIAM and refined through CPM and SCM are validated against field data using the parameter K.The results are consistent with existing research findings,thereby confirming the reliability of the proposed methodology.Furthermore,the study investigates the relationship between tunnel depth(h0)and tunnel radius(R),and explores the interactions among the layer number of stratum(n),elastic modulus(E),and layer thickness(H).A reduction coefficient(η)is introduced to improve the model's accuracy.The proposed approach is applied to nine tunnel engineering cases,and comparisons with measured data demonstrate its accuracy and practical applicability.
基金supported by the National Natural Science Foundation of China (Grant Nos.52008039 and 52308425)the Natural Science Foundation of Hunan Province (Grant No.2021JJ40592).
文摘Deep excavations in silt strata can lead to large deformation problems,posing risks to both the excavation and adjacent structures.This study combines field monitoring with numerical simulation to investigate the underlying mechanisms and key aspects associated with large deformation problems induced by deep excavation in silt strata in Shenzhen,China.The monitoring results reveal that,due to the weak property and creep effect of the silt strata,the maximum wall deflection in the first excavated section(Section 1)exceeds its controlled value at more than 93%of measurement points,reaching a peak value of 137.46 mm.Notably,the deformation exhibits prolonged development characteristics,with the diaphragm wall deflections contributing to 39%of the overall deformation magnitude during the construction of the base slab.Subsequently,numerical simulations are carried out to analyze and assess the primary factors influencing excavation-induced deformations,following the observation of large deformations.The simulations indicate that the low strength of the silt soil is a pivotal factor that results in significant deformations.Furthermore,the flexural stiffness of the diaphragm walls exerts a notable influence on the development of deformations.To address these concerns,an optimization study of potential treatment measures was performed during the subsequent excavation of Section 2.The combined treatment approach,which comprises the reinforcement of the silt layer within the excavation and the increase in the thickness of the diaphragm walls,has been demonstrated to offer an economically superior solution for the handling of thick silt strata.This approach has the effect of reducing the lateral wall displacement by 83.1%and the ground settlement by 70.8%,thereby ensuring the safe construction of the deep excavation.
基金supported by the National Natural Science Foundation of China(42102208)the National Natural Science Foundation of China(41972256).
文摘Coal mining in groundwater-rich coal fields will trigger failure of overlying strata,resulting in the formation of water-conducting fracture zone(WCFZ)and potentially leading to water-inrush accidents.In this study,a reliability model with consideration of spatial variability and uncertainty of strength parameters was proposed to predict the failure behaviour of overlying strata during coal mining in groundwater-rich coalfields.Rock strength parameters,including cohesion,internal friction angle,uniaxial tensile strength,and softening coefficient,are treated as random variables to determine the rock failure uncertainty.The experimental results of these geomechanical parameters at different positions are interpolated by the Kriging interpolation method.Spatially,the interpolated values are arranged as the average value of each random variable to demonstrate their autocorrelation.Furthermore,based on Mohr–Coulomb yield criterion,a performance function is deduced to calculate the failure probabilities of overburden rocks to evaluate the spatial scale of WCFZ.As a typical case,the failure features of adjacent overlying strata of No.7121 mining face in Qidong Coal Mine is analyzed.The results show that the risks of water-inrush are high when the mining face advances to 260–380 m and 1120–1240 m,which aligns with both field monitoring results and borehole observation results.The proposed model holds significant implications for prevention of water-inrush accidents in groundwater-rich coal mines.
基金supported by the National Natural Science Foundation of China(No.51978019)the Natural Science Foundation of Beijing Municipality(No.8222004),China.
文摘Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogeneous strata,with limited research conducted on the upper loose and lower dense strata.Active instability tests are conducted in this study,in concert with the digital image correlation(DIC)technique,to investigate the effects of different water pressure ratios in upper loose and lower dense water-rich strata.The accuracy of these model tests is verified using numerical simulations.The results indicate that as water pressure ratio decreases,there is an increase in both the peak displacement of surface settlement and the seepage path range of water ahead of the excavation face expands.In contrast,decreasing water pressure ratio will break the limit equilibrium state of the strata faster,cause the earth pressure on the cutterhead to change more rapidly,and increase the instability range of the strata.
文摘煤矿井下复杂施工环境导致超前钻探中钻具响应与岩性映射关系通常难以直接建立,制约岩性识别精度。针对此问题,构建了聚晶金刚石复合片(PDC)钻头-钻杆破岩仿真模型,揭示了不同钻进条件下钻具对复合岩层的响应特征:固定钻速,提升转速会使钻头扭矩降低且波动减弱,而钻压波动相对稳定;固定转速,提升钻速会使钻压与扭矩同步升高。钻杆三轴向振动加速度随转速增大而增大,随钻速增大呈先减小后增大趋势。在岩性界面处,上述参数呈现突变特征,表明多参数联合可作为岩性识别特征。基于此,提出了一种融合双向长短期记忆网络(BiLSTM)、注意力机制与KAN(Kolmogorov-Arnold Network)的岩性识别模型——BiLSTM-Att-KAN,以KAN替代BiLSTM模型中多层感知机(MLP)分类器,突破MLP因使用Sigmoid/Rectified Linear Unit(ReLU)等固定激活函数导致的非线性映射局限,可提高复杂岩性识别精度。利用仿真数据和实际数据进行模型测试,结果表明:BiLSTM-Att-KAN在仿真数据集上的识别准确率达91.64%,优于K近邻、随机森林等传统分类模型,提升幅度7.00%~22.08%;在实际训练钻孔数据测试集与独立测试数据上的准确率分别为86.81%和85.28%,验证了模型有效性,可为煤系地层岩性识别提供技术支撑。
