Analytical and experimental studies on installation of a suction caisson with tampered tip in clay     

Shuwang Yan  Jingjing Zhang  Jian Chu  Zhiliang Huo 《Marine Georesources & Geotechnology》2017,35(3):435-440

Concrete suction caissons have been successfully used as breakwaters or seawalls in recent years. The relative large wall thickness-to-diameter ratio of a concrete caisson can lead to the formation of a full soil heave plug that may cause difficulties in the installation of concrete caisson in clay. One way to overcome this limitation is to use a tampered tip for the caisson wall. An analytical method is proposed in this article to calculate the minimum suction pressure required to penetrate a caisson and the maximum allowable suction pressure that can be applied to avoid too much soil heave plug during the installation of the suction caisson. Four model tests were conducted in normally consolidated clay to study the installation process of a concrete suction caisson with tampered tip and to verify the proposed analytical method. The height of the soil heave plug in the caisson with a tampered tip is observed to be about half of that in the caisson with a flat tip.  相似文献   

Algorithm for generation of stratigraphic profiles using cone penetration test data     

《Computers and Geotechnics》2017

Cone Penetration Test (CPT) data are often used directly in the design of shallow and deep foundations and many other applications. To produce more cost-effective designs, it is advantageous to use CPT data to establish stratigraphic profiles as well. Algorithms to generate a stratigraphic profile using data from an individual CPT sounding and a Soil Behavior Type (SBT) chart as inputs are presented. Two SBT charts from the literature were selected and modified to eliminate ambiguity in soil classification. Novel algorithms were developed for handling the occurrence of thin layers within a stratigraphic profile to account for the fact that the standard CPT cone cannot accurately sense layers with thickness below a certain limit and a representative cone resistance cannot be obtained if the layer is too thin. Likewise, the algorithms prevent the creation of a soil profile with adjacent layers of essentially the same soil by consolidating layers appropriately. The algorithms presented generate a design soil profile, produced using a precise classification based on soil type and state and by elimination of artificial layering, that can be more effectively used in design.  相似文献   

Effects of soil anisotropy on a soil structure interaction in a heat exchanger pile     

《Computers and Geotechnics》2017

A coupled thermal-hydro-mechanical computational modeling of actual field tests, which had been conducted on an end bearing heat exchanger pile, has been carried out. Results of a conventional triaxial test program, which was performed during the site investigation, indicated that two soil layers were anisotropic. A simplified form of a transverse isotropy was used to model the response of these layers. Additional analyses were carried out for completely isotropic soil layers. Comparisons between the measurements obtained during the field testing and predictions of the computational models showed a very good to excellent agreement. Overall the anisotropic model performed better than the isotropic model.  相似文献   

Spatial-temporal Variations of H2 Concentration in Soil Gas in the Seismic Fault Zone Produced by the Wenchuan MS 8.0 Earthquake     

Zhou Xiaocheng  Shi Hongyu  Chen Chao  Zeng Linghua  Sun Fengxia  Li Jing  Chen Zhi  Lü  Chaojia  Huang Dan  Du Jianguo 《地球科学进展》2017,32(8):818-827

Degassing of Hydrogen (H₂) from fault may be a good indicator of fault activity. The concentration of H₂ in soil gas in the seismic surface rupture zone produced by the Wenchuan M_S 8.0 earthquake was investigated in twenty three measuring regions in order to explore the relationship between the spatio-temporal variations of H₂ concentration in soil gas along the seismic rupture zone and the vertical displacements and aftershocks activities. The results indicated: ① the sources of H₂ were directly related to from the release of natural gas reservoirs; ②the average concentration of H₂ in soil gas spatially decreased from Yingxiu to Nanba; ③the magnitudes of the H₂ concentration anomalies declined significantly with time. It is very significant to study the variation tendency of atmospheric environment with further research of degassing of H₂ from faults.  相似文献   

土壤地球化学测量在文登青庄地区金矿勘查中的应用          下载免费PDF全文

张朋朋 《山东国土资源》2017,33(4)

为有效、准确的寻找金矿床,结合文登青庄地区基岩出露情况,选择开展了1∶1万土壤地球化学测量。该次工作测网选择100 m×40 m,局部加密至100 m×20 m,采集20~30 cm深处的BC层土壤,过40目样筛,过筛后样品重量均大于150 g,分析Au,Ag,Cu,Pb,Zn,As,Bi,Mo等8种元素。通过对各元素分析结果进行R型聚类分析,认为将As,Sb元素作为寻找Au矿的主要指示元素在该区不适用,该区Au与Bi的相关性较好。通过合理确定各元素的背景值和异常下限,圈定单元素异常190处,根据元素组合特征圈定综合异常19处,其中AP7,AP19成矿条件较好,划分为乙1类异常,重点开展异常查证工作。通过探槽施工、化验分析等异常查证工作,在两个异常内均发现金矿(化)体,样品中金品位(0.30~3.64)×10-6,确定了土壤地球化学测量在该区找矿工作中的适用性和有效性。区内发现的金(矿)化体赋存于蚀变破碎带内,矿化蚀变主要有黄铁矿化、硅化、绿泥石化,与邻近的西院下金矿相似,初步确定区内寻找的金矿床类型应为构造角砾岩-碎裂岩型金矿床。  相似文献   

Estimating soil moisture using remote sensing data: A machine learning approach   总被引：4，自引：0，他引：4  

Sajjad Ahmad  Ajay KalraHaroon Stephen 《Advances in water resources》2010

Soil moisture is an integral quantity in hydrology that represents the average conditions in a finite volume of soil. In this paper, a novel regression technique called Support Vector Machine (SVM) is presented and applied to soil moisture estimation using remote sensing data. SVM is based on statistical learning theory that uses a hypothesis space of linear functions based on Kernel approach. SVM has been used to predict a quantity forward in time based on training from past data. The strength of SVM lies in minimizing the empirical classification error and maximizing the geometric margin by solving inverse problem. SVM model is applied to 10 sites for soil moisture estimation in the Lower Colorado River Basin (LCRB) in the western United States. The sites comprise low to dense vegetation. Remote sensing data that includes backscatter and incidence angle from Tropical Rainfall Measuring Mission (TRMM), and Normalized Difference Vegetation Index (NDVI) from Advanced Very High Resolution Radiometer (AVHRR) are used to estimate soil water content (SM). Simulated SM (%) time series for the study sites are available from the Variable Infiltration Capacity Three Layer (VIC) model for top 10 cm layer of soil for the years 1998–2005. SVM model is trained on 5 years of data, i.e. 1998–2002 and tested on 3 years of data, i.e. 2003–2005. Two models are developed to evaluate the strength of SVM modeling in estimating soil moisture. In model I, training and testing are done on six sites, this results in six separate SVM models – one for each site. Model II comprises of two subparts: (a) data from all six sites used in model I is combined and a single SVM model is developed and tested on same sites and (b) a single model is developed using data from six sites (same as model II-A) but this model is tested on four separate sites not used to train the model. Model I shows satisfactory results, and the SM estimates are in good agreement with the estimates from VIC model. The SM estimate correlation coefficients range from 0.34 to 0.77 with RMSE less than 2% at all the selected sites. A probabilistic absolute error between the VIC SM and modeled SM is computed for all models. For model I, the results indicate that 80% of the SM estimates have an absolute error of less than 5%, whereas for model II-A and II-B, 80% and 60% of the SM estimates have an error less than 10% and 15%, respectively. SVM model is also trained and tested for measured soil moisture in the LCRB. Results with RMSE, MAE and R of 2.01, 1.97, and 0.57, respectively show that the SVM model is able to capture the variability in measured soil moisture. Results from the SVM modeling are compared with the estimates obtained from feed forward-back propagation Artificial Neural Network model (ANN) and Multivariate Linear Regression model (MLR); and show that SVM model performs better for soil moisture estimation than ANN and MLR models.  相似文献   

Three-dimensional simulation of track on poroelastic half-space vibrations due to a moving point load   总被引：1，自引：0，他引：1  

Honglei Sun  Yuanqiang Cai  Changjie Xu 《Soil Dynamics and Earthquake Engineering》2010

An analytical approach is used to investigate dynamic responses of a track system and the poroelastic half-space soil medium subjected to a moving point load under three-dimensional condition. The whole system is divided into two separately formulated substructures, the track sub-system and the ground. The ballast supporting rails and sleepers is placed on the surface of the ground. The rail is modeled by introducing the Green function for an infinitely long Euler beam subjected to the action of the moving point load and the reaction of sleepers represented by a continuous mass. Using the double Fourier transform, the governing equations of motion are then solved analytically in the frequency–wave-number domain. The time domain responses are evaluated by the inverse Fourier transform computation for a certain load velocities. Computed results show that dynamic responses of the soil medium are considerably affected by the fluid phase as well as the load velocity.  相似文献   

People’s perception and socioeconomic determinants of soil erosion:A case study of Samanalawewa watershed,Sri Lanka   总被引：3，自引：0，他引：3  

E.P.N. UDAYAKUMARA  R.P.SHRESTHA  L.SAMARAKOON  D.SCHMIDT-VOGT 《国际泥沙研究》2010,25(4):323-339

Though soil erosion is an important concern in Sri Lanka, there is a dearth of baseline information on soil erosion in many ofits watersheds, which obstructs monitoring of soil erosion and mitigating its effects. In order to assess soil erosion in a critical watershed and to identify its determinants, the Samanalawewa watershed, which contains one of the main hydropower generating reservoirs in Sri Lanka, was selected for this study. Remote-sensing (RS) and geographic information system (GIS) based modeling...  相似文献   

Response of circular flexible foundations subjected to horizontal and rocking motions     

《Soil Dynamics and Earthquake Engineering》2015

A methodology using modal analysis is developed to evaluate dynamic vertical displacements of a circular flexible foundation resting on soil media subjected to horizontal and rocking motions. The influence of the soil reaction forces on the foundation is considered by introducing modal impedance functions, which can be determined by an efficient procedure with ring elements. The displacements of the foundation can then be easily solved by modal superposition. Parametric studies for modal responses of the flexible foundation indicate that the coupled response of the foundation is significantly influenced by relative stiffness among the foundation and the soil medium, vibration frequency range, foundation mass, and boundary contact conditions. The welded boundary condition should be considered to predict the coupling response while the relaxed boundary condition may be used to predict approximately the vertical displacements. As a foundation with a relative stiffness ratio more than three, it is found that the foundation can be considered as rigid to calculate coupling displacements. For a slightly flexible foundation, considerations of three modes are sufficient enough to obtain accurate foundation responses. Moreover, at low frequencies, the coupling effect due to higher mode can be neglected.  相似文献   

General formulation and solution procedure for harmonic response of rigid foundation on isotropic as well as anisotropic multilayered half-space     

《Soil Dynamics and Earthquake Engineering》2015

A general formulation and solution procedure are proposed for harmonic response of rigid foundation on multilayered half-space. It is suitable for isotropic as well as anisotropic soil medium. The wave motion equation is formulated in frequency wave-number domain in the state space. A hybrid approach is proposed for its solution, where the precise integration algorithm (PIA) is employed to carry out the integration. Very high accuracy can be achieved. The mixed variable form of wave motion equation enables the assembly of layers simple and convenient. The surface Green׳s function is regarded as rigorous, because it is free from approximations and discretization errors. The algorithm is unconditionally stable. The numerical implementation is based on algebraic matrix operation. Numerical examples of vibration of rigid foundation validate the efficiency and accuracy of the proposed approach.  相似文献