Numerical evaluation of land subsidence induced by dewatering in deep foundation pit

To predict the behavior of land subsidence due to groundwater withdrawal, a 3D numerical model is established. The model takes the confined aquifer and soft deposit of Ningbo into account. According to the pumping test data, changing regulations of groundwater level, and land subsidence during dewatering are analyzed. Comparison between the calculated value and measured value shows that the 3D model simulates the measured value fairly well. The future behavior of land subsidence during dewatering period provides the scientific basis for the construction of deep foundation.     

高速公路水泥固化盐渍土的试验研究

针对津汕高速公路盐渍土路基处治工程,通过室内试验分析了公路路基不同深度氯盐渍土的物理力学及化学性质。进行了大量水泥固化盐渍土室内试验,分析了水泥掺入量、龄期、含盐量和试验加荷速率等对水泥固化盐渍土抗压强度的影响规律,初步探讨了水泥加固盐渍土的机理,分析了水泥土搅拌桩在盐渍土路基处理中应用的可能性,为盐渍土地区公路路基水泥搅拌桩处理技术的设计和施工提供依据。     

Field Tests for Investigating the Extraction Rate of Piles Using a Vibratory Technique

Factors directly affecting the extraction rate of the piles pulled out by a vibratory pulling system are summarized and classified into five categories (excitation force, resistance, vibration amplitude, pile plumbness keeping, and slowing down at the later stage) from the mechanics and engineering practice. Field tests on steel sheet piles extracted by vibratory technique in different soil conditions are conducted to ascertain how these factors affect the extraction rate of a pile with regard to three major actors of vibratory pile pulling: the pile to be extracted, the selected pulling system, and the imposed soil conditions. The extraction rates of three different sheet pile types (having up to four different lengths) pulled out by two different vibratory pulling systems are documented. The piles with different lengths and types, pulled out with or without a clutch, have different extraction rates. The working parameters governing the vibratory hammer, such as excitation force and vibration amplitude, exert significant influences on the rate of pile extraction, especially in the early stages of up-lift process. The extraction rate of the piles driven in different soil conditions is uniform because different extraction resistances mainly refer to shaft friction. The properties of the pile-soil interface influence the extraction rate of the piles, and the extraction rate decreases with the time for which the piles have been buried in the earth.     

振动压路机振动轮—土壤系统模态分析

在试验研究基础上，建立了振动压路机振动轮—土壤系统数学模型，应用复模态结构振动理论，计算土壤压实过程中系统模态参数和系统响应，得出系统中前机架或振动轮响应的变化规律，从而构成了识别不同压实阶段的理论基础。     

A simplified analysis method for the lateral deformation of braced excavations

Pile-anchor retaining structure is widely used in foundation pit engineering and side slope engineering in many countries. In contrast to strut, pile-anchor retaining structure has its typical features and advantages. It does not occupy the internal space of the foundation pit, and the project cost is much lower. Accurate prediction of the lateral displacement of the retaining structure is very important in the design stage. A simplified analysis method and several calculation assumptions of the lateral deformation of pile-anchor retaining structures are set up according to the engineering features. The expression function of lateral displacement versus depth is solved by means of a fitted function and the quasi-elastic summation method. The parameters are obtained through the stiffness equation of the anchors and the principle of minimum potential energy. The analytical evaluation of the lateral deformation curve is then completed, whose applicability is proved through practical engineering.     

振动压路机动态性能试验研究

通过对振动压路机振动轮－土壤系统和驾驶员乘坐舒适性的理论分析，选择典型样机按其主要作业工况，现场测试主要振动响应参数，由测试结果对理论分析的主要结论予以验证。     

公路桥头路基EPS垫层的隔振分析

公路桥头路基跳车现象是道路中普遍存在的问题,目前国内外尚没有非常有效的处理措施,虽有大量的相关研究,但分析与研究内容多局限于减小地基的附加应力以达到控制沉降差的目的。试图从动力学角度出发,对柔性路面路基的桥头路基跳车进行动力分析,并针对当前施工中的新技术一采取聚苯乙烯泡沫塑料工法(EPS)的隔振性能进行了有限元分析,以期能为工程设计与施工提供依据。     

高频振动打桩机理的试验研究

扼要评述高频振动沉桩机理,叙述在不同相对密度的饱和砂土中,通过小型模型试验研究模拟桩体贯入深度随激振频率(20~80 Hz)的变化规律。试验结果初步表明,增高振动频率可使饱和砂土液化加速,土阻力相应地快速减小,显著提高沉桩效率。