The study focused on one of the important contemporary environmental problems, land deterioration, carried out on a semi-desert rangeland constrained by aridity, in an area stretching between two small cities （Solouk...The study focused on one of the important contemporary environmental problems, land deterioration, carried out on a semi-desert rangeland constrained by aridity, in an area stretching between two small cities （Solouk and A1-Abyar） south of the city of Benghazi in north eastern Libya. The vegetation analysis revealed that the plant life is mainly confined to wadis （valleys）. Average vegetation cover was ranging between 39.53% and 69.20%. Biomass was ranging between 28.33 gm/m2 and 129.42 gm/m2, （average soil depth was between 30 cm and 50 cm）, meanwhile 25% of the area is covered by hummocks. The total number of sampled soil seed bank was 25,870 seed/m2, in which the important forage family Fabaceae constituted 450 seed/m2. Life forms spectrum was： 55.2% Therophytes, 26.3% Chamaeopytes, 11.4% Cryptophytes and 7.1% Phanerophytes. Alpha diversity 1.3%-3.4%, and Beta diversity 11.9%-77.6%. The soil showed low organic matter content an lean to alkalinity. The study showed that the area is characterized by harsh climate elements which led to land degradation in the form of low productivity, retrogressive succession, soil erosion, and sandy encroachment from the south desert area. In the last decades the land degradation was accelerated by the accumulative anthropogenic.展开更多
Excavation Damaged Zone(EDZ)scope is important for optimizing excavation and support schemes in deep underground caverns.However,accurately predicting the full EDZ scope within the surrounding rock masses of deep unde...Excavation Damaged Zone(EDZ)scope is important for optimizing excavation and support schemes in deep underground caverns.However,accurately predicting the full EDZ scope within the surrounding rock masses of deep underground caverns during excavation remains a pressing problem.This study presents a comprehensive EDZ scope prediction approach(CESPA)for the brittle surrounding rock masses of deep underground caverns by coupling numerical simulation with quantitative analysis of borehole wall images and ultrasonic test results.First,the changes in both P-velocity(V_(p))and joint distribution of the surrounding rock masses before and after excavation damage are captured using ultrasonic tests and borehole digital cameras.Second,the quality Q-parameters of the surrounding rock mass before and after excavation damage are preliminarily rated with the rock mass descriptions provided by borehole wall images,and the rock mass V_(p)-parameter values are determined according to the V_(p)-borehole depth curves.Third,the Q-parameter ratings are further finely adjusted by updating the related Q-values to be similar with the Q-values estimated by V_(p)-parameter values.Fourth,the initial and residual mechanical parameters for the rock mass deterioration model(RDM)are estimated by the adjusted Q-parameter ratings based on the modified Q-based relations,and the elastic modulus deterioration index(EDI)threshold to describe the EDZ boundary is determined with the V_(p)-parameter values.Finally,EDZ scope is predicted using the elastoplastic numerical simulation with RDM and EDI based on the mechanical parameter estimates and EDI threshold.Analyses of applications in Sub-lab D1 in Jinping II project show that CESPA can provide a reliable and operable solution for predicting full EDZ scopes within the brittle surrounding rock masses of deep underground caverns.展开更多
三峡库区周期性水位升降引起的消落带岩体劣化对典型危岩岸坡稳定性具有重大影响。基于野外调研及地勘资料,采用通用离散单元法程序(universal distinct element code,简称UDEC)研究了消落带劣化区形态对近水平层状高陡危岩岸坡的稳定...三峡库区周期性水位升降引起的消落带岩体劣化对典型危岩岸坡稳定性具有重大影响。基于野外调研及地勘资料,采用通用离散单元法程序(universal distinct element code,简称UDEC)研究了消落带劣化区形态对近水平层状高陡危岩岸坡的稳定性影响。研究表明:目前三峡库区巫山段的近水平层状危岩岸坡消落带岩体劣化严重,在不同消落带劣化区存在紧密层状、松散碎裂状、溶蚀凹腔状、含挤压碎裂带等典型消落带劣化区形态;含有第1种消落带劣化区形态的危岩岸坡稳定性较好,危岩体位移较小,失稳模式为滑移破坏;含有第2种消落带劣化区形态的危岩岸坡危岩体先向坡内偏移,其后随着消落带岩体支撑强度弱化向坡外倾倒破坏;含有第3种消落带劣化区形态的危岩岸坡危岩体向坡外位移较大,失稳模式为倾倒破坏;含有第4种消落带劣化区形态的危岩岸坡稳定性主要受挤压破碎带的力学性质控制,易产生沿破碎带切割面的旋转滑移破坏;通过对以上4种劣化区形态的危岩岸坡增加防治加固措施,危岩体的变形位移得到了不同程度的有效控制。展开更多
文摘The study focused on one of the important contemporary environmental problems, land deterioration, carried out on a semi-desert rangeland constrained by aridity, in an area stretching between two small cities （Solouk and A1-Abyar） south of the city of Benghazi in north eastern Libya. The vegetation analysis revealed that the plant life is mainly confined to wadis （valleys）. Average vegetation cover was ranging between 39.53% and 69.20%. Biomass was ranging between 28.33 gm/m2 and 129.42 gm/m2, （average soil depth was between 30 cm and 50 cm）, meanwhile 25% of the area is covered by hummocks. The total number of sampled soil seed bank was 25,870 seed/m2, in which the important forage family Fabaceae constituted 450 seed/m2. Life forms spectrum was： 55.2% Therophytes, 26.3% Chamaeopytes, 11.4% Cryptophytes and 7.1% Phanerophytes. Alpha diversity 1.3%-3.4%, and Beta diversity 11.9%-77.6%. The soil showed low organic matter content an lean to alkalinity. The study showed that the area is characterized by harsh climate elements which led to land degradation in the form of low productivity, retrogressive succession, soil erosion, and sandy encroachment from the south desert area. In the last decades the land degradation was accelerated by the accumulative anthropogenic.
基金funded by the National Natural Science Foundation of China under Grant Nos.51979268,U1765206,41877256。
文摘Excavation Damaged Zone(EDZ)scope is important for optimizing excavation and support schemes in deep underground caverns.However,accurately predicting the full EDZ scope within the surrounding rock masses of deep underground caverns during excavation remains a pressing problem.This study presents a comprehensive EDZ scope prediction approach(CESPA)for the brittle surrounding rock masses of deep underground caverns by coupling numerical simulation with quantitative analysis of borehole wall images and ultrasonic test results.First,the changes in both P-velocity(V_(p))and joint distribution of the surrounding rock masses before and after excavation damage are captured using ultrasonic tests and borehole digital cameras.Second,the quality Q-parameters of the surrounding rock mass before and after excavation damage are preliminarily rated with the rock mass descriptions provided by borehole wall images,and the rock mass V_(p)-parameter values are determined according to the V_(p)-borehole depth curves.Third,the Q-parameter ratings are further finely adjusted by updating the related Q-values to be similar with the Q-values estimated by V_(p)-parameter values.Fourth,the initial and residual mechanical parameters for the rock mass deterioration model(RDM)are estimated by the adjusted Q-parameter ratings based on the modified Q-based relations,and the elastic modulus deterioration index(EDI)threshold to describe the EDZ boundary is determined with the V_(p)-parameter values.Finally,EDZ scope is predicted using the elastoplastic numerical simulation with RDM and EDI based on the mechanical parameter estimates and EDI threshold.Analyses of applications in Sub-lab D1 in Jinping II project show that CESPA can provide a reliable and operable solution for predicting full EDZ scopes within the brittle surrounding rock masses of deep underground caverns.
文摘三峡库区周期性水位升降引起的消落带岩体劣化对典型危岩岸坡稳定性具有重大影响。基于野外调研及地勘资料,采用通用离散单元法程序(universal distinct element code,简称UDEC)研究了消落带劣化区形态对近水平层状高陡危岩岸坡的稳定性影响。研究表明:目前三峡库区巫山段的近水平层状危岩岸坡消落带岩体劣化严重,在不同消落带劣化区存在紧密层状、松散碎裂状、溶蚀凹腔状、含挤压碎裂带等典型消落带劣化区形态;含有第1种消落带劣化区形态的危岩岸坡稳定性较好,危岩体位移较小,失稳模式为滑移破坏;含有第2种消落带劣化区形态的危岩岸坡危岩体先向坡内偏移,其后随着消落带岩体支撑强度弱化向坡外倾倒破坏;含有第3种消落带劣化区形态的危岩岸坡危岩体向坡外位移较大,失稳模式为倾倒破坏;含有第4种消落带劣化区形态的危岩岸坡稳定性主要受挤压破碎带的力学性质控制,易产生沿破碎带切割面的旋转滑移破坏;通过对以上4种劣化区形态的危岩岸坡增加防治加固措施,危岩体的变形位移得到了不同程度的有效控制。
