Fiber optic monitoring of an anti-slide pile in a retrogressive landslide

Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method.However,due to many assumptions involved in calculation,the analytical models cannot be fully applicable to complex site situations,e.g.landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein.In view of this,the combination of distributed fiber optic sensing(DFOS)and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area,China.Brillouin optical time domain reflectometry(BOTDR)was utilized to monitor the strain distri-bution along the pile.Next,by analyzing the relative deformation between the pile and its adjacent inclinometer,the pile-soil interface separation was profiled.Finally,the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method.According to the ratio of calculated internal forces to the design values,the working conditions of the anti-slide pile could be evaluated.The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system,and can quantitatively evaluate its working conditions.

Centrifuge and numerical modeling of h-type anti-slide pile reinforced soil-rock mixture slope

Due to the loose structure,high porosity and high permeability of soil-rock mixture slope,the slope is unstable and may cause huge economic losses and casualties.The h-type anti-slide pile is regarded as an effective means to prevent the instability of soilrock mixture slope.In this paper,a centrifuge model test was conducted to investigate the stress distribution of the h-type anti-slide pile and the evolution process of soil arching during the loading.A numerical simulation model was built based on the similar relationship between the centrifuge model and the prototype to investigate the influence factors of the pile spacing,anchored depth,and crossbeam stiffness,and some recommendations were proposed for its application.The results show that the bending moment distribution of the rear pile exhibits Wshaped,while for the front pile,its distribution resembles V-shaped.The soil arching evolution process during loading is gradually dissipated from bottom to top and from far to near.During the loading,the change of bending moment can be divided into three stages,namely,the stabilization stage,the slow growth stage,and the rapid growth stage.In engineering projects,the recommended values of the pile spacing,anchored depth,and crossbeam stiffness are 4.0d,2.0d,and 2.0EI,where d and EI are the diameter and bending stiffness of the h-type anti-slide pile respectively.

Anchoring Depth Research of Anti-Slide Piles of Anchor Bar in Soil

The model test result of earth force in the side of anti-slide pile of anchor bars was introduced.There are three groups of the tests.The loads were on the back side of the slope in two groups.The other one was loaded just behind the pile by the jack.In order to get the force of the soil,some earth-pressure boxes were used to get the earth pressure on the side of the piles.The part of the max pressure and the earth pressure was mainly focused under the slip line

Interval finite element method and its application on anti-slide stability analysis

The problem of interval correlation results in interval extension is discussed by the relationship of interval-valued functions and real-valued functions. The methods of reducing interval extension are given. Based on the ideas of the paper, the formulas of sub-interval perturbed finite element method based on the elements are given. The sub-interval amount is discussed and the approximate computation formula is given. At the same time, the computational precision is discussed and some measures of improving computational efficiency are given. Finally, based on sub-interval perturbed finite element method and anti-slide stability analysis method, the formula for computing the bounds of stability factor is given. It provides a basis for estimating and evaluating reasonably anti-slide stability of structures.

Shaking table test for reinforcement of soil slope with multiple sliding surfaces by reinforced double-row anti-slide piles

Despite the continuous advancements of engineering construction in high-intensity areas,many engineering landslides are still manufactured with huge thrust force,and double-row piles are effective to control such large landslides.In this study,large shaking table test were performed to test and obtain multi-attribute seismic data such as feature image,acceleration,and dynamic soil pressure.Through the feature image processing analysis,the deformation characteristics for the slope reinforced by double-row piles were revealed.By analyzing the acceleration and the dynamic soil pressure time domain,the spatial dynamic response characteristics were revealed.Using Fast Fourier Transform and half-power bandwidth,the damping ratio of acceleration and dynamic soil pressure was obtained.Following that,the Seism Signal was used to calculate the spectral displacement of the accelerations to obtain the regional differences of spectral displacement.The results showed that the overall deformation mechanism of the slope originates from tension failure in the soil mass.The platform at the back of the slope was caused by seismic subsidence,and the peak acceleration ratio was positively correlated with the relative pile heights.The dynamic soil pressure of the front row piles showed an inverted"K"-shaped distribution,but that of the back row piles showed an"S"-shaped distribution.The predominant frequency of acceleration was 2.16 Hz,and the main frequency band was 0.7-6.87 Hz;for dynamic soil pressure,the two parameters became 1.15 Hz and 0.5-6.59 Hz,respectively.In conclusion,dynamic soil pressure was more sensitive to dampening effects than acceleration.Besides,compared to acceleration,dynamic soil pressure exhibited larger loss factors and lower resonance peaks.Finally,back row pile heads were highly sensitive to spectral displacement compared to front row pile heads.These findings may be of reference value for future seismic designs of double-row piles.

New method of designing anti-slide piles——the strength reduction FEM

At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be easily obtained. In this paper,the authors applied the strength-reduction finite element method (FEM) to several design cases of anti-slide piles. Using this method,it is possible to take the pile-soil interactions into consideration,obtain reasonable resistance in front of pile and the distributions of thrust and resistance,and reasonable lengths of anti-slide piles. In particular,the thrust and resistance imposed on embedded anti-slide piles can be calculated and composite anti-slide pile structures such as anchored piles and braced piles can be optimized. It is proved through the calculation examples that this method is more reliable and economical in the design of anti-slide pile.

Sensitivity analysis of factors affecting gravity dam anti-sliding stability along a foundation surface using Sobol method

The anti-sliding stability of a gravity dam along its foundation surface is a key problem in the design of gravity dams.In this study,a sensitivity analysis framework was proposed for investigating the factors affecting gravity dam anti-sliding stability along the foundation surface.According to the design specifications,the loads and factors affecting the stability of a gravity dam were comprehensively selected.Afterwards,the sensitivity of the factors was preliminarily analyzed using the Sobol method with Latin hypercube sampling.Then,the results of the sensitivity analysis were verified with those obtained using the Garson method.Finally,the effects of different sampling methods,probability distribution types of factor samples,and ranges of factor values on the analysis results were evaluated.A case study of a typical gravity dam in Yunnan Province of China showed that the dominant factors affecting the gravity dam anti-sliding stability were the anti-shear cohesion,upstream and downstream water levels,anti-shear friction coefficient,uplift pressure reduction coefficient,concrete density,and silt height.Choice of sampling methods showed no significant effect,but the probability distribution type and the range of factor values greatly affected the analysis results.Therefore,these two elements should be sufficiently considered to improve the reliability of the dam anti-sliding stability analysis.

Experimental study on seismic reinforcement of bridge foundation on silty clay landslide with inclined interlayer

A shaking table test for a bridge foundation reinforced by anti-slide piles on a silty clay landslide model with an inclined interlayer was performed.The deformation characteristics of the bridge foundation piles and anti-slide piles were analyzed in different loading conditions.The dynamic response law of a silty clay landslide with an inclined interlayer was summarized.The spacing between the rear anti-slide piles and bridge foundation should be reasonably controlled according to the seismic fortification requirements,to avoid the two peaks in the forced deformation of the bridge foundation piles.The“blocking effect”of the bridge foundation piles reduced the deformation of the forward anti-slide piles.The stress-strain response of silty clay was intensified as the vibration wave field appeared on the slope.Since the vibration intensified,the thrust distribution of the landslide underwent a process of shifting from triangle to inverted trapezoid,the difference in the acceleration response between the bearing platform and silty clay landslide tended to decrease,and the spectrum amplitude near the natural vibration frequency increased.The rear anti-slide piles were able to slow down the shear deformation of the soil in front of the piles and avoid excessive acceleration response of the bridge foundation piles.

钢纤维高强混凝土二桩承台受力特性有限元分析

为进一步研究钢纤维高强混凝土二桩承台内部传力机理,在钢纤维高强混凝土二桩承台模型试验的基础上,考虑混凝土塑性损伤模型(CDP),利用ABAQUS进行钢纤维高强混凝土二桩承台的受力特性分析,并与试验结果对比,阐明竖直荷载作用下承台的破坏形态、开裂荷载和极限荷载,以及承台钢筋和混凝土的应力变化特征,并在此基础上探究承台的传力机理。结果表明:二桩承台破坏形态的有限元分析结果与承台试验结果吻合较好;随着承台厚度和钢纤维体积率的增加,二桩承台承载力显著提高;选用合适的配筋率和钢纤维高强混凝土可有效提高承台承载力;钢纤维高强混凝土二桩承台传力机理符合“拉杆拱”模型。

桩间距对桩板结构应力变形的影响研究

依托改建铁路漳泉肖线白濑水利枢纽工程影响区段改线工程项目,基于SAP2000软件,研究下穿桥梁地段铁路桩板结构的桩间距(等量桩径d)对板内正、负弯矩和变形的影响,并与规范进行比较。结果表明:横向桩间距不变时,随着纵向桩间距的增加,板内正、负弯矩及桩顶竖向变形均线性增加,板内最大负弯矩出现在板中央桩顶处;板内最大正弯矩逐渐由横向桩间向纵向桩间转移;当纵向桩间距为4d~5d时,板内各点处正、负弯矩和竖向变形均相对较小且大致相当,证明规范中桩间距规定的合理性;当纵向桩间距超过9d时,板内底部正弯矩较大,需进行配筋设计。

Pre-Stressed Rope Reinforced Anti-Sliding Pile

Pre-stressed rope reinforced anti-sliding pile is a composite anti-sliding structure. It is made up of pre-stressed rope and general anti-sliding pile. It can bring traditional anti-sliding pile＇s retaining performance into full play, and to treat with landslide fast and economically. The difference between them is that the pre-stressed rope will transfix the whole anti- sliding pile through a prearranged pipe in this structure. The working mechanics, the design method and economic benefit are studied. The results show that the pre-stressed rope reinforced anti-sliding pile can treat with the small and middle landslides or high slopes well and possess the notable advantage of technology and economic.

Application of strength reduction method to dynamic anti-sliding stability analysis of high gravity dam with complex dam foundation

Considering that there are some limitations in analyzing the anti-sliding seismic stability of dam-foundation systems with the traditional pseudo-static method and response spectrum method, the dynamic strength reduction method was used to study the deep anti-sliding stability of a high gravity dam with a complex dam foundation in response to strong earthquake-induced ground action. Based on static anti-sliding stability analysis of the dam foundation undertaken by decreasing the shear strength parameters of the rock mass in equal proportion, the seismic time history analysis was carried out. The proposed instability criterion for the dynamic strength reduction method was that the peak values of dynamic displacements and plastic strain energy change suddenly with the increase of the strength reduction factor. The elasto-plastic behavior of the dam foundation was idealized using the Drucker-Prager yield criterion based on the associated flow rule assumption. The result of elasto-plastic time history analysis of an overflow dam monolith based on the dynamic strength reduction method was compared with that of the dynamic linear elastic analysis, and the reliability of elasto-plastic time history analysis was confirmed. The results also show that the safety factors of the dam-foundation system in the static and dynamic cases are 3.25 and 3.0, respectively, and that the F2 fault has a significant influence on the anti-sliding stability of the high gravity dam. It is also concluded that the proposed instability criterion for the dynamic strength reduction method is feasible.

浅谈“PLIE”在芭蕾基础训练中的应用

在芭蕾舞训练和表演过程中,PLIE是最重要的动作之一,很多学者将其比喻为地基性动作,训练得如果到位,可以使表演者的芭蕾舞整体动作以及舞台表现力得到很大程度的提升。因此,在芭蕾舞训练过程中,应当对PLIE的训练引起足够的重视,本文主要针对PLIE的训练和应用展开了论述,希望能够为芭蕾舞表演提供一些理论参考依据。

Study on distribution rule of sliding pushing force and remnant resistant sliding force acting on anti-sliding pile

Anti-slide pile is one of the important methods to administer landslide geological disaster because of its advantages.It plays important role in administering landslide.It is a premise of reasonable economy and technological advance to know the distribution rule and feature of the force between anti-sliding pile and surrounding rock.To determine the sliding force and remnant resistant sliding force,according to need of study,this paper sets up the geological model and mechanics model in term of a typical landslide,and analyzes the effect rule of sliding body distortion,strength and gravity to the pushing force and remnant resistant sliding force by use of the numerical model.The distribution rule of pushing force and remnant resistant sliding force of the type of landslide is given.

论plie在芭蕾训练中的作用与意义

Plie对于芭蕾训练来说有着至关重要的意义。作为训练中的活动动作plie,使人体最复杂最容易损伤之一的关节——膝关节,得到适当的热身,同时也让腿部肌肉得到充分的舒展。舞者通常会在芭蕾基础训练时,容易忽视这个最基础的动作,忽略它的作用,及其存在的意义。一、Plie动作原理分析一名优秀的芭蕾舞演员,必须清楚的了解此动作的原理及身体肌肉、关节的应用方法,才能真正的掌握这个动作。作为舞者为什么要做这个单一、枯燥的练习?

头孢曲松/他唑巴坦对产β-内酰胺酶大肠埃希菌后效应的研究

目的探讨头孢曲松/他唑巴坦复方(CRO/TAZ)对产β-内酰胺酶大肠埃希菌的体外抗菌活性(MIC)、抗生素后效应(PAE)、β-内酰胺酶抑制剂后效应(PLIE)和抗生素亚抑菌浓度后效应(PASME)。方法采用琼脂二倍稀释法测定CRO/TAZ和CRO对产4种酶型β-内酰胺酶E.coli菌株的MIC;以微量接种菌落计数法测定菌落形成单位(CFU),绘制细菌生长曲线,并计算PAE、PLIE和PASME。结果CRO/TAZ复方对产β-内酰胺酶菌株的MIC较CRO单方降低都在8倍以上;无论CRO单方还是CRO/TAZ复方均无长的PAE(-0.59～0.85 h);PLIE和PASME随着菌株β-内酰胺酶酶型的不同而不同,相同酶型的菌株PLIE和PASME很接近;PLIE(0.62～3.22 h)和大多数PASME(0.12～5.61 h)都较其PAE长,而且对CRO单方MIC较小的菌株,其PAE、PLIE和PASME较长。结论PLIE和PASME的长短可能与β-内酰胺酶酶型有关。对于有较长PLIE和PASME的菌株,在制定临床给药方案时可适当延长给药间隔;PAE、PLIE和PASME理论为研究抗菌药物药效学和设计合理给药方案、优化给药模式提供重要参考和新思路。

抗滑桩与粉喷桩联合法在软基路堤稳定中的应用

抗滑桩是防治岸坡、山体滑移常用的一种支挡结构 ,但用它解决软基路堤的稳定性国内尚无先例 ,本文结合连云港至徐州高速公路的工程实例对抗滑桩与粉喷桩相结合在这方面的成功应用情况做了介绍 ,其中包括桩的受力分析、设计计算方法、适用条件等。本工程中采用的抗滑桩就是普通的钻孔灌注桩 ,其施工工艺简单 ,质量可靠 。

重庆地质灾害研究与防治

本文结合典型工程实例探索性地论述了重庆地质灾害研究与防治的主要问题、基本理论、基本方法及管理体制的改革与完善。

云南普洱茶渥堆过程中的主要微生物初探

通过对云南普洱茶渥堆过程中微生物的种类、数量变化和形态特征的研究表明:主要微生物有黑曲霉属(Aspergilliusniger)、青霉属(Penicllium)、根霉属(Rhizopus)、灰绿曲霉属(Aspergilliusgloucus)、酵母属(Saccharomyces)、细菌类(Bacterium).黑曲霉数量始终处于优势地位,酵母菌的总数居次,细菌数目极少.

深层搅拌桩弥补钻孔灌注桩承载力不足的尝试

针对某工程钻孔灌注桩的单桩进行静、动试验,对单桩极限承载力不能满足设计要求进行了分析。提出了用柔性深层搅拌桩弥补刚性灌注桩承载力不足的处理措施,对刚、柔性桩受力和变形协调性进行了分析,并使二者共同作用。处理结果表明:这种方法既经济,又便于施工,能完全达到设计要求,对类似地基事故处理具有参考作用。