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2018 Vol. 37, No. 2

Display Method:
Spatial variability of soil moisture on hillslope in typical karst peak-cluster depression areas
LI Chunmao, CHEN Hongsong, XU Qinxue, WU Pan, FU Zhiyong
2018, 37(2): 159-167. doi: 10.11932/karst20180201
Abstract:
The study area is located in Guilin, Guangxi, with a land area of approximately 3,000 m2. The area is characterized by humid subtropical monsoonal climate, with the average annual temperature 18.7 ℃ and the average annual rainfall of 1,785.2 mm; and it’s rainy season is generally from April to September, which belongs to the typical karst peak-cluster depression landforms. The study area include the hillslopes and the below terraces, and the terraces were previously transformed from hillslopes and used by villagers for the orangery and vegetable gardens. The exposed rate of rock in the middle of the hillslopes is more than 70%; and a large amount of exposed rock divide their soil into patches in the form of "rock gap soil" and "stone bowl soil" while retaining the upper native shrub. In order to reveal the spatial variability characteristics of surface soil moisture in typical karst peak-cluster depression hillslopes with strong artificial disturbance and land use diversity, selecting the slopes of the typical peak-cluster depressions and using grid method to measure the soil moisture content in the dry season (December) and the rainy season (May), the spatial variability of soil moisture on hillslopes was analyzed by geostatistics. The results show that,(1) Compared with the slope of single land use,the surface soil moisture of the typical peak-cluster hillslopes is that undisturbed natural vegetation area located above the slope is significantly higher than artificial transformation of the region located below the slope,soil water content of sloping woodland(32.8%)that locating on top of the slope and undisturbed was significantly higher than terraced fields (24.2%) , terraced orange garden (20.0%),terraced vegetable garden (22.0%) and bare land (23.5%) during the dry season. In rainy season,bare land (30.2%) and terraced origin garden (32.1%) had increased obviously and the terraced fields were drastically reduced (17.8%),while sloping woodland (32.2%) remained the highest;(2)The spatial structure ratio is 21.0% and 8.7% during the dry and rainy season, respectively, indicating that the spatial correlation of the rainy season is better;the coefficient of variation of the surface soil moisture was 20.1% and 31.7% during dry season and rainy season,which are both belonging to moderate spatial variability;the range of surface soil moisture during the rainy season (77.5 m) was significantly higher than that of dry season (8.0 m), which can be seen that the spatial variation structure of rainy season is better; (3)The change of soil moisture in the surrounding space of bare stone decreases with the increase of distance;soil moisture in the surrounding space of terrace bank is decreasing with increasing distance.
Study on soil microbial quantity and biomass developed from different carbonate-rock and soil thickness:A case study of Huaxi district in Guiyang
ZHOU Wei, YAN Min, SU Chunhua, LI Ling, LEI Zhangqin
2018, 37(2): 168-174. doi: 10.11932/karst20180202
Abstract:
The Huaxi district of Guiyang is located in the center of Guizhou Province. The soil thickness developed from carbonate rocks has a wide range. The soil quality greatly changes with different soil thickness, especially the characteristic of microorganism.Based on field investigation, 3 kinds of soil types, namely thin soil, middle soil and thick soil were studied in Huaxi, Guiyang. The number and biomass of microorganism under different soil thickness in karst area were studied. The results showed that the quantity of bacteria, fungi and antinomies gradually increased with the soil thickness increase. Compared with the fungi and antinomies, bacteria occupy an absolute advantage in soil microbes. They account for 88.13%, 85.71%, 87.36%, 85.00% and 77.78% of soil in different soils thickness developed from limestone and dolomite respectively. In limestone soil, the content of microbial biomass carbon,nitrogen and phosphorus gradually increased from the thin soil to the thick soil, of which the increasing amount were 15.15 mg·kg-1,2.82 mg·kg-1and 0.18 mg·kg-1, respectively. And in dolomite soil, the content of microbial carbon, nitrogen and phosphorus increased from the thin soil to the middle soil, of which the increasing amount were 5.13 mg·kg-1, 0.39 mg·kg-1and 0.10 mg·kg-1, respectively. The content of microbial nitrogen and phosphorus in the soil developed from limestone is significantly higher than that developed from dolomite under the same soil layer, of which the difference in middle soil was the largest, with a difference of 0.90 mg·kg-1and 0.21 mg·kg-1respectively. In comparison, this content of microbial biomass carbon in the soil of limestone is higher than that in the dolomite soil, which is 17.31 mg·kg-1high. The result of correlation analysis showed that the pH value had a significant effect on the microbial biomass carbon and phosphorus (p<0.05), the total phosphorus content has a significant effect on microbial biomass phosphorus(p<0.01).
Corrosion effects and environmental correlation of bryophytes on limestone in Guiyang karst park
SHEN Jiachen, ZHANG Zhaohui, WANG Huihui, HUANG Huan, WANG Zhihui
2018, 37(2): 175-184. doi: 10.11932/karst20180203
Abstract:
Bryophytes are important habitants in the karst area, and they are of great significance in biological geology and ecological geology to study the corrosion in karst area. The relationship among bryophyte diversity, dissolution forms and environmental factors was studied in Nanshilin, Guiyang kast park through field investigations and lab experiments, The results show that: 49 taxa in 27 genera of 14 families of bryophytes were identified in the study area. According to the morphology, the corrosion results could be divided into six types: corrosion hole, corrosion pit, corrosion cone, corrosion groove, corrosion trough and corrosion basin. The diversity index of bryophytes showed a tendency of rising first and then decreasing in the following three stages:corrosion hole-corrosion cone-corrosion pit-corrosion basin, corrosion groove- corrosion pit-corrosion basin and corrosion trough-corrosion pit-corrosion basin,of which the minimum indices of bryothytes diversity occurred in corrosion hole, corrosion cone and corrosion groove being 6.232, 8.524, and 7.490, respectively. The bryophyte diversity index reached a maximum value of 18.219 in the corrosion pit, and then decreased to 11.949 in corrosion basin. The uniformity showed an upward trend, from 0.880, 0.862, 0.916 to 0.953, then dropped to 0.876 at the stage of corrosion basin. The environment plays an important role in the occurrence of corrosion patterns. Under the second grade condition (temperature of 17.5-21.4 ℃, humidity of 57.7%-72.6%RH, light of 2,700-5,900 Lux), the bryophytes have the strongest shaping effect on limestone. The change of dissolution patterns is often accompanied by the succession of the moss community. The bryophytes have a strong shaping effect on the formation of dissolution patterns.
Habitat degradation degree in response to land use change in Guiyang City from 2005 to 2015
HAN Huiqing, WANG Zhe, ZHANG Yingjia, SU Zhihua, YIN Changying
2018, 37(2): 185-191. doi: 10.11932/karst20180204
Abstract:
Guiyang City is an important central city in southwest China. It is located in a typical karst ecological vulnerability region. In recent years, the land use of the city has been reshaped by a series of ecological protection planning and rapid economic development, which has heavily influenced on habitat quality. In order to investigate such influence and associated spatial pattern on the urban habitat degradation degree in both karstic and ecologically vulnerable region, this paper attempts to analyze the characteristics of land use change between 2005 and 2015 in the city, based on the land use data, by using Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model. The results show that, (1) Urban construction land, rural settlement and forestland have a sharp increase trend, while paddy field and dry land have an obvious decrease trend from 2005 to 2015 in Guiyang City. The other land use types have little change in this decade. It is prominent that numerous dry lands have been converted to forestland, land for construction and rural settlement, as well as paddy field converted to forestland. (2) During the past ten years, the habitat degradation degree generally has a decreasing trend over the city, which is dominated by slight decrease. The rise of the degradation degree mainly occurs in the south area, while the decreases of the degree are located in the north, east and west of the city. (3) Decreases of high value and low value are main types in change of habitat degradation degree hot-spots in Guiyang City. Increasing region of high value is mainly situated in south part of Guiyang, while increasing region of low value and decreasing regions of high value and low value are mainly in north, east and west parts of Guiyang City. Area change of threat land use types (e.g. paddy field, dry land, urban construction land, rural settlement, road, industrial and mining land) exerts a positive impact on habitat degradation degree while area change of natural land use types (e.g. forestland, shrub, grassland, water) has a negative impact on habitat degradation degree. The conversions from paddy field and dry land to urban construction land, rural settlement and forestland due to Green for Grain Project and rapid urbanization are main reasons for the change of habitat degradation degree in Guiyang City.
Hydrochemical characteristics and sources of Nanpanjiang and Beipanjiang river basins during dry seasons
MA Kuo, WU Qixin, HAN Guilin, DONG Aiguo
2018, 37(2): 192-202. doi: 10.11932/karst20180205
Abstract:
Water samples were collected in dry seasons to analyze the hydrochemical components of Nanpanjiang and Beipanjiang basins, the upper reaches of the Pearl River. The results show that pH values of the water from the two catchments,ranges from7.85 to 8.75 during dry seasons, slightly alkaline,with an average TDS of 358 mg·L-1. The anions are dominated by HCO3- and SO42- with the mean equivalent concentration accounting for 65% and 26% of the total anions, respectively. The main cations are Ca2+and Mg2+, accounting for 65% and 24% of the total cations, respectively. Compared with the research about the concentrations of major ions in wet seasons, the concentrations of Ca2+, Mg2+, Na+, SO42-, HCO3-, and Cl- in dry seasons are higher, while K+ and NO3- contents almost remain the same. Piper diagrams, end members of lithology and ion concentration ratios collectively indicate that the chemical composition of river water is mainly controlled by carbonate weathering where sulfuric acid and carbonic acid both participate. Nanpanjiang and Beipanjiang are all influenced by agricultural activities. In addition, Beipangjiang is mainly affected by coal mining and coal-combustion industry, while Nanpanjiang is mainly affected by wastewater from industries at upper reach and the cities and towns along the river. Compared with previous data, it is found that the impact of anthropogenic activities on water has increased over the past 15 years.
Construction and application of water resource security evaluation model in karst area:A case study of Guizhou Province
LIU Liying, YANG Qingwei, ZENG Yixiao, HE Xiujuan, GUAN Dongjie
2018, 37(2): 203-210. doi: 10.11932/karst20180206
Abstract:
Karst area is rich in water resources in the traditional sense. However, the surface water resources are deficient, and the groundwater resources are abundant, which forms a binary relation in water structure system. So the ecological status of this area is extremely important. The karst landform is widely distributed in Guizhou. With the rapid development of social economy, the situation of water resources security has attracted much attention. In order to analyze the current situation of water resources security in karst area, this study takes the typical karst area Guizhou Province as the research object. Fourteen indexes were selected from four aspects, including water supply, society, economy and ecology, to establish the evaluation index system of water resources security. Meanwhile, the entropy weight method and fuzzy mathematics comprehensive evaluation model were combined to perform quantitative evaluation of this study, so as to evaluate the water resources security of Guizhou Province in the 9 cities and in each year from 2005 to 2014. According to the results, Guiyang, Qiandongnan, and Tongren were in good level, Zunyi, Qiannan, Bijie and Qianxi’nan were in the general level, Anshun and Liupanshui were in a poor level. In the past year from 2005 to 2014, the security of water resources in Guizhou Province is relatively stable, all in the general level, but it was on the rise. This is due to the correct development ideas in recent years in Guizhou Province, the government has realize the importance of sustainable development of the water resources, and began to strengthen the scientific management of water resources. During this period, the government has attached great importance to ecological protection, and has put the coordination of economic growth, population, resources and environment in a prominent strategic position. In addition, the improvement of urban sewage treatment capacity and enterprise waste water discharge standards also played an important role in the change of water resources security.However, the water resources security in Guizhou is at a general level, and has a great development potential. Overall, the current situation for water resources in Guizhou is in a non-equilibrium fluctuating state under the pressures of economic development and human disturbance. With the contradiction between ecological environment and economic development intensified, Guizhou Province should focus on the water environment safety management, adjust the industrial structure so as to make the economic and social benefits become a supplement of ecological benefits
Hydrochemical characteristics and geochemical sensitivity of groundwater in typical karst hilly regions:A case study of Eastern Wugang
LUO Fei, SU Chuntian, PAN Xiaodong, YANG Yang, ZHAO Guangshuai
2018, 37(2): 211-217. doi: 10.11932/karst20180207
Abstract:
This study investigated hydrochemical characteristics and geochemical sensitivity of groundwater in a typical karst hilly region. The results indicate that Ca2+ and Mg2+ are the main cations and HCO3- and NO3- are the main anions in the karst groundwater system, which are affected by water-rock interaction and human activities; groundwater system, which is affected by water-rock interaction and human activities. The result also indicates the ratio of Mg2+/ Ca2+, controlled by lithology, is the highest in the dolomite second highest in the limestone dolomite, and the lowest in limestone. In general, the karst groundwater in the study area shows a high geochemical sensitivity which follows the order as HCO3->Ca2+>Mg2+>NO3->SO42->Cl->Na+>K+. In particular,the cation Ca2+ is the most sensitive, followed by Mg2+, while HCO3- is the most sensitive inthe anions, followed by NO3-. The sensitivity level of the karst groundwater in the study area is classified by the most sensitive factor HCO3-. Consequently, the low sensitive water spots account for only 7.27%, the medium sensitive ones account for about 25.45%, while the highly sensitive account for about 67.28%. These statistic results of the geochemical sensitivity division show that the protection of groundwater is very important and urgent.
Study on multi-objective emergency allocation of groundwater resources for small towns in karst area: A case study of Zhijin county
SONG Xiaoqing, QU Qiunan, YANG Zhenhua
2018, 37(2): 218-227. doi: 10.11932/karst20180208
Abstract:
In order to solve the problem of discrepancy between the water supply and water demand in urban area and to put forward an emergency allocation scheme for groundwater resources in karst areas under drought conditions. In this paper, we take Zhijin county north Zhucang water storage syncline structure as an example; and the runoff modulus method was used to simulate the development and utilization of the water resources in the study area. According to the principles of mixed integer linear programming and multi-objective linear programming, following the principle of "giving priority to the protection of domestic water and taking into account the maximization of economic benefits", a drought emergency allocation model for the resources at different targets , i.e. E-MIP (Emergency Multi-objective Integer Programming) model, was constructed and applied to the study area. As a result, the groundwater resources in the city of Zhijin county emergency scheme during 2010-2030 were put forward. The research result shows that, (1) In the north of Zhucang anticline, the exposed water from the fractured-karst aquifers mainly discharges through the underground river, with an average flow rate of 62.04 m3·s-1; and in porous-fractured bedrock are springs mainly discharge groundwater in an manner of dispersion, with an average flow of only 2.14 m3·s-1.(2) The elevated degree of drought not only restricts the amount of water resources used, but also directly stimulates and improve the water use efficiency and social and economic benefits. In the period of 2010-2030, the severe drought rate in Zhijin county was 21.25% which was lower than that of the mild drought, but its social and economic benefits increased by 5.84 times. Meanwhile, the supply and demand balance of groundwater resources under severe drought has changed from 35.68% surplus rate to 47.98% water shortage rate, but the GDP of Zhijin urban area was 47.96×108 yuan, rising to 280.27×108 yuan year by year. (3) The emergency allocation principle of groundwater resources is a priority to protect residents living water demand; secondly, according to the water use efficiency and the weight order, the distribution of the surplus groundwater resources is allocated; in addition, the emergency allocation scheme of water resources for the years of 2020 and 2030 in Zhijin was further predicted, respectively which has laid the foundation for improving the state of emergency under the rational and scientific use of resources. The above research indicates that with the increase of water use efficiency, the social and economic benefits of the allocation of groundwater resources in the northern part of Zhucang syncline will gradually increase, and domestic water will become the key object of emergency allocation of water resources, so that making the social benefits greatly exceed its economic benefits.
Simulation of future scenarios of climate change in the middle and upper reaches of the Peal River using the Statistical Down Scaling Model (SDSM)
XU Yan, WANG Shijie, BAI Xiaoyong, LI Xiongyao, SHI Xiaoming, TIAN Yichao, WU Luhua
2018, 37(2): 228-237. doi: 10.11932/karst20180209
Abstract:
Due to the vulnerability and sensitivity of the karst eco-system, the prediction of future climate change in the karst area has great significance to reasonably exploit the regional resources and effectively protect the ecological environment. However, the research on the climate downscaling in the karst area is nearly blank. In this paper, the daily mean temperature and daily precipitation from 13 meteorological stations in the Hongliujiang zone of the Pearl River Basin during 1961-2001 were used as the predictors. Moreover, the NCEP reanalysis data was used as the forecast factor. The SDSM model was applied to predict the trends of temperature and precipitation in future years under SRES A2 and B2 emission scenarios of the HadCM3 model. The results show that,(1) SDSM mode can be applied in the accurate simulation of the temperature and precipitation in the study area, and the deterministic coefficient of observation and simulation value is about 99% and 65% respectively; (2) Compared with the reference period, the future temperature and precipitation in the A2 and B2 scenarios show a clear upward trend until the end of the 21th century, and the increment is increasing with time prolonged. Meanwhile,by the end of 21th century,the relative variation of the future mean annual temperature in the A2 and B2 scenarios are +3.39 ℃ and +2.49 ℃ respectively, and the 117.30 % and 80.90 % growth respectively in daily precipitation under the A2 and B2 scenarios; (3) The rise of temperature is the most obvious in autumn and spring, and the precipitation increase is the largest in summer. Therefore, this analysis not only provides the foundation data and the theoretical basis for setting strategies, but also has great significance for impact study of climate changes in karst areas.
Study of rainfall-runoff simulation and recession flow in Pingzhihe river karst basin
CHEN Lihua, YANG Kaipeng, HUANG Duyi
2018, 37(2): 238-244. doi: 10.11932/karst20180210
Abstract:
The karst area in Guangxi Zhuang Autonomous Region is widespread, with complicated hydrogeological conditions and frequent flooding occurence. The Pingzhihe river basin, which is selected as the study area, originates from Baise City of Guangxi and is a first tributary of the Red River. The main stream of the Pingzhihe river is 81 km long, with a total drainage area of 963 km2. Karst region accounts for about 50% of the drainage area and the average annual precipitation is 1,517 mm. Combined with the structural characteristics of the karst aquifer system and the measured data, in this paper, we analyzed the pattern of groundwater drainage in Pingzhihe river basin and built a rainfall-runoff simulation program suitable for this basin. ArcGIS software is used to construct the digital basin for the study area which is divided into nine sub-basins. At the same time, based on the hydrological data of Tonglao, Liming reservoir and other 8 rainfall stations and Fengwu hydrological stations from 2010 to 2015, the research work has been carried out. Among them, six uni-modal flooding events happened in 2010 to 2015 were selected, from which their recession curves were plotted on semilog coordinates. The curves collectively show that when the logarithm of the flow rate is close to 2.5, the turning point appears. Thus two sections of the curves are linearly fitted and their attenuation coefficients can be obtained from the curve fitting. The results show that the subsurface flow can be divided into rapid and slow underground runoffs. Simplified Boussinesq exponential decay equation was used to calculate the regression coefficients for the two parts of runoffs. The extinction coefficient of rapid underground runoff KQ was 0.988-0.995 and the slow runoff extinction coefficient KL was 0.997-0.999. Based on the traditional Xin’anjiang river model with one linear reservoir, a linear reservoir is added to simulate the rapid underground runoff and the slow underground runoff, respectively, to construct a rainfall-runoff simulation program. The calculation program was compiled with Matlab 2014 software. With the maximum of the deterministic coefficient as the optimization objective, the genetic algorithm is used to determine the model parameters.7 floods from 2011 to 2015 were selected as regular analog floods, and 8 floods were selected as verified floods for runoff simulation. According to the "hydrological forecasting code (GB / T 22482-2008)" assessment criteria, the qualified rate of regular analog was 85.71%, and the average coefficient of determination was 0.846; the qualified rate of verification was 75%, the average deterministic coefficient of 0.893 reached B-grade accuracy. Compared with the traditional Xin’anjiang river model, the average deterministic coefficient and qualified rate of the improved Xin’anjiang river model have been improved. The simulation results show that the simulation scheme is suitable for the Pingzhihe river basin, and can provide reference for the rainfallrunoff simulation and flood forecasting in other similar karst areas in Guangxi.
Research on the water level of anti-floating of building structure based on long-term boreholes and rainfall observations
HU Zheng, CHEN Zaiqian
2018, 37(2): 245-253. doi: 10.11932/karst20180211
Abstract:
This paper studies anti-floating groundwater level of main body structure foundation pit, with a case study of the metro line 2 at Sanqiao station, Guiyang. The relationship between long-term groundwater level monitoring data and rainfall data was analyzed. On this basis, a method for the calculation of anti-uplift water level values was put forward. Main result shows that,(1) anti-uplift water value consists of three parts, i.e. the highest groundwater level during the site investigation, the groundwater level rise by unexpected recharge and the maximum groundwater fluctuation rate compared to that of the site exploration period; (2) The groundwater levels monitored fluctuate seasonally which commonly increase in rainy season and decline in dry season, with the highest water levels appear in June and July; (3) The linear relationship between the change of the groundwater level and the change of monthly rainfall was obtained by the linear fitting of the rainfall in April, May and June; (4) Combined with the historical rainfall, the maximum increase of the groundwater level in the field area is 2.26 m, and the anti-floating water level in the field area is 1,128.46 m.
Study on spatial-temporal differentiation of tourism climate comfort in Guangxi based on DEM
SHEN Xibing
2018, 37(2): 254-264. doi: 10.11932/karst20180212
Abstract:
This work is based on digital elevation model (DEM) and 3S as well as conventional meteorological observation data of 74 points in Guangxi from 1981 to 2010. The objective is to analyze spatial distribution characteristics of the temperature, relative humidity, wind velocity, temperature-humidity index, wind chill index, the clothing index and integrated tourism comfort in varied terrains. Combined with spatial distribution of 307 2Agrade scenic spots of Guangxi in 2015, this study obtains the following results. Because of time difference, the best travel time periods of most areas in Guangxi are January, February, March, October, November, during which the temperature of these areas is maintained 15-25 ℃, and not the rainy season. On climate comfort, April and December are more suitable for travel. Because Guangxi is located in the south of China, heavy rain and high temperature occur over the same periods in June, July and August which most unsuitable for travel. As for seasons, the order of climate comfort for tourism is winter> autumn > spring > summer. Because of spatial differences, the areas with tourism comfort period of 6 months only cover 0.12% of Guangxi, scattered in the northwest of Xilin county in western Guangxi and the north of Ziyuan county in northern Guangxi, where no tourist spot above 2A level is present. The areas with tourism comfort period of 7 months are mainly in the west-southwest and northwest of Guangxi, which lies in Ziyuan county of western Guangxi, Bobai county and Hepu county of southern Guangxi,and Wuzhou county and hezhou county of southern Guangxi, which cover 36.78% of whole Guangxi area. There are 72 tourist spots above 2A level, accounting for 23.5% the total number of tourist spots. The areas with a tourism comfort period of 8 months are the most widely distributed, which cover 63.1% of entire Guangxi. There are 235 above 2A level tourist spots, accounting for 76.5% the total number of tourist spots in 2015, mainly distributed in central, southern and northern Guangxi.
Characteristics and environmental significance of isotopes record from cave drip water and recent deposit in Naduo cave, Guizhou
MAO Qingya, WANG Jianli, WANG Jialu, LI Wen
2018, 37(2): 265-271. doi: 10.11932/karst20180213
Abstract:
To explore the cave drip water and the variation characteristics of its corresponding oxygen isotopes in modern deposits and their significance to the climatic environment, the atmospheric precipitation outside the Naduo cave in Guizhou, cave pool water, six drip points and their corresponding modern deposits oxygen stable isotopes have been monitored for the past 2 years. The results show that theδ18O in atmospheric precipitation, drip water, and deposits of Naduo cave are generally lower than those in most other southern regions. However, the seasonal variation ofδ18O from all three sources is significant. For example, theδ18O in atmospheric precipitation outside Naduo cave and in cave pool water both have seasonal characteristics that are higher in the dry season and lower in the wet season, and can basically reflect the climate change in the area where the cave is located. Though theδ18O in deposits and drip water have similar seasonal variation, they show a very different pattern from theδ18O in the atmospheric precipitation. This may be the result of the combination of regional topography, karst surface zone regulation, and atmospheric circulation.
Joint inference of multi-channel transient surface wave method and microtremor method to investigate the structure and thickness of the overburden layer in the typical area of karst collapse
ZHANG Wei, GAN Fuping, LIANG Donghui, HAN Kai, LIU Wei
2018, 37(2): 272-279. doi: 10.11932/karst20180214
Abstract:
In order to obtain the structure and thickness distribution of the overburden layer in the typical karst collapse area in large scale, multi-channel transient surface wave method and microtremor method were used to carry out field survey in the typical karst collapse area of Dongquan commune in Liucheng country, Liuzhou city.Based on the relationship between the characteristic frequency and the thickness of the formation extracted by the microtremor method, combined with the existing borehole data, the functional relationship between the thickness of the covering layer and the characteristic frequency is obtained and the thickness distribution of the overburden layer can be derived. The shear wave velocity distribution of the overburden layer was obtained from the dispersion characteristics of the surface wave, based on which the structural distribution of the overburden layer can be derived. With the structure and thickness distribution of cover layer, four local faults or dissolution trenches in the survey area were inferred. The study shows that the structure and thickness distribution of the overburden layer can be effectively deduced by using the characteristic frequency of microtremor and the dispersion characteristics of the surface wave.
Application of geophysical prospecting and hydrogeological analysis in borehole siting in the karst area:A case study of ZK3 well in Luojiaba, Qianjiang district
CAO Rui, RAN Yu, LYU Yuxiang, GUO Chuandao, LI Dehai, WANG Jia
2018, 37(2): 280-285. doi: 10.11932/karst20180215
Abstract:
The combined use of geophysical prospecting and hydrogeological analysis can help to improve the success rate of borehole siting in the karst area. The advantage of this method is elaborated in this paper with the case study of well ZK3 in Luojiaba, Qianjiang district. It is confirmed that groundwater occurrence in the karst area is dominated by geomorphology, topography, geological structure and lithology. The low lying syncline with specific lithologic configurations is the primary target area for borehole siting. Proper geophysical techniques can be applied based on the geology and topography of the study area. The interpretation result of audio magnetotelluric method can be reliable when the study area is characterized with the following conditions, such as partially covered, deep groundwater and the presence of large variety in electrical resistivity between stratums.
Electromagnetic interference analysis of ground penetrating radar and its application in karst detection in tunnel
LI Junjie, ZHU Honglei, ZHAO Guojun, XIA Zhiqiang, GUO Jiahao
2018, 37(2): 286-293. doi: 10.11932/karst20180216
Abstract:
The Ground Penetrating Radar (GPR) was applied to detect karst caves in a tunnel in Thousand Island Lake water-supply pipeline project. The difference of radar anomalies between inclined electromagnetic interference and karst cave was analyzed. Then the properties and spatial distribution characteristics of the tunnel bottom of the karst cave were deduced by analyzing radar profiles and single-channel time-frequency spectrum of the suspected abnormal area. The water-filled karst caves were characterized by the phase axis fault,strong amplitude and high energy attenuation in the radar reflected profiles. The amplitude of high-frequency interference is smaller than abnormal area and the energy does not appear in accordance with the law that it should decay over time. The results of radar provide an accurate reference for the safety of tunnel construction.
Critical conditions for karst collapses in the Yongwen Middle School, Guiyang, China
JIANG Fuwei, LI Liang, CHEN Hang
2018, 37(2): 294-299. doi: 10.11932/karst20180217
Abstract:
There are 7 karst collapses happened and 1 potential collapse site in the Yongwen Middle School of Guiyang city, which pose a serious threat on the safety of teachers and students and property there. This site is characterized by highly soluble bedrock, thin covering clay layer and strong groundwater erosion;these have caused the site to be a high-risk karst collapse in this area. Through laboratory simulation test,it is realized that the karst collapse hazard follpwed a fissure-seepage-disintegration model. The results also show that the soil water content is critical in the disintegration and the formation of karst collapses. Furthermore, 8 sets of undisturbed samples with different water content are used to conduct disintegration tests. They demonstrate that the water content of 26.8% is the critical value to trigger karst collapse, while 0~26.8% is the condition for generation of such a risk at the site.
Analysis on karst development and water burst in a subway station
ZHANG Keneng, ZHANG Yue, LIAO Yang, WAN Haoran, XU Peihao, ZHANG Yunyi
2018, 37(2): 300-306. doi: 10.11932/karst20180218
Abstract:
Water and mud burst occurs commonly in karst region,which causes many problems to the engineering construction of subway station in the water-rich karst area and the fault rupture zone.It is of great importance to the design and construction of subway station excavation by investigating of the characteristics of the karst development and water burst.In this paper, the treatment of karst water burst in the deep pit of a subway station in Guiyang is presented. Based on site investigation and theoretical analysis, the characteristics of karst development and water burst in the subway station was studied and summarized with the aid of 3D geological software. The spatial relationship between the karst, the fault zone and the subway is established and represented by 3D geological model. This study can be very useful to the design and construction of similar subway station in terms of karst hydrogeology and the treatment of water burst.
Water disaster analysis and numerical simulation of a karst tunnel in a highway of Guangdong Province
ZHANG Yanlong, TIAN Qingyan, ZHANG Jiantong
2018, 37(2): 307-313. doi: 10.11932/karst20180219
Abstract:
The key factors to calculate the tunnel water inflow are studied based on the actual situation of a highway tunnel in the karst area. The tunnel water inflow rate is quantitatively analyzed with precipitation, rainfall intensity and infiltration intensity. According to the actual situation of Dabaoshan engineering site, precipitation infiltration method and underground runoff modulus method are applied to calculate the tunnel water inflow at the entrance on both sides in the wet season, and the maximum possible water inflow volume is analyzed under the heavy rainfall condition.The results show that the drainage capacity of the tunnel theoretically meets the requirement of drainage in the wet season, but will be affected by the heterogeneity of the material and the engineering, and the long-term effect of clogging.The impact factors of karst tunnel water in highway are identified in Guangdong area. Karst tunnel simulation models are established for both critical state and failure state of the water pressure.The results show that the critical value of water pressure increases with the thickness of the lining structure.