Three-Dimensional Conjugate Tooth Surface Design and Contact Analysis of Harmonic Drive with Double-Circular-Arc Tooth Profle

A three-dimensional conjugate tooth surface design method for Harmonic Drive with a double-circular-arc tooth profle is proposed. The radial deformation function of the fexspline (FS), obtained through Finite Element (FE) analysis, is incorporated into the kinematics model. By analyzing the FS tooth enveloping process, the optimization of the overlapping conjugate tooth profle is achieved. By utilizing the hobbing process, the three-dimensional machinable tooth surface of FS can be acquired. Utilizing the coning deformation of the FS, simulations are conducted to analyze the multi-section assembly and meshing motion of the machinable tooth surface. The FE method is utilized to analyze and compare the loaded contact characteristics. Results demonstrate that the proposed design method can achieve an internal gear pair consisting of a circular spline with a spur gear tooth surface and the FS with a machinable tooth surface. With the rated torque, approximately 24% of the FS teeth are engaged in meshing, and more than 4/5 of the tooth surface in the axial direction carries the load. The contact patterns, maximum contact pressure, and transmission error of the machinable tooth surface are 227.2%, 40.67%, and 71.24% of those on the spur gear tooth surface, respectively. It clearly demonstrates exceptional transmission performance.

Slope deformation partitioning and monitoring points optimization based on cluster analysis

The scientific and fair positioning of monitoring locations for surface displacement on slopes is a prerequisite for early warning and forecasting.However,there is no specific provision on how to effectively determine the number and location of monitoring points according to the actual deformation characteristics of the slope.There are still some defects in the layout of monitoring points.To this end,based on displacement data series and spatial location information of surface displacement monitoring points,by combining displacement series correlation and spatial distance influence factors,a spatial deformation correlation calculation model of slope based on clustering analysis was proposed to calculate the correlation between different monitoring points,based on which the deformation area of the slope was divided.The redundant monitoring points in each partition were eliminated based on the partition's outcome,and the overall optimal arrangement of slope monitoring points was then achieved.This method scientifically addresses the issues of slope deformation zoning and data gathering overlap.It not only eliminates human subjectivity from slope deformation zoning but also increases the efficiency and accuracy of slope monitoring.In order to verify the effectiveness of the method,a sand-mudstone interbedded CounterTilt excavation slope in the Chongqing city of China was used as the research object.Twenty-four monitoring points deployed on this slope were monitored for surface displacement for 13 months.The spatial location of the monitoring points was discussed.The results show that the proposed method of slope deformation zoning and the optimized placement of monitoring points are feasible.

Shear sliding of rough-walled fracture surfaces under unloading normal stress

Through high-precision engraving,self-affine sandstone joint surfaces with various joint roughness coefficients(JRC=3.21e12.16)were replicated and the shear sliding tests under unloading normal stress were conducted regarding various initial normal stresses(1e7 MPa)and numbers of shearing cycles(1 e5).The peak shear stress of fractures decreased with shear cycles due to progressively smooth surface morphologies,while increased with both JRC and initial normal stress and could be verified using the nonlinear Barton-Bandis failure criterion.The joint friction angle of fractures exponentially increased by 62.22%e64.87%with JRC while decreased by 22.1%e24.85%with shearing cycles.After unloading normal stress,the sliding initiation time of fractures increased with both JRC and initial normal stress due to more tortuous fracture morphologies and enhanced shearing resistance capacity.The surface resistance index(SRI)of fractures decreased by 4.35%e32.02%with increasing shearing cycles due to a more significant reduction of sliding initiation shear stress than that for sliding initiation normal stress,but increased by a factor of 0.41e1.64 with JRC.After sliding initiation,the shear displacement of fractures showed an increase in power function.By defining a sliding rate threshold of 5105 m/s,transition from“quasi-static”to“dynamic”sliding of fractures was identified,and the increase of sliding acceleration steepened with JRC while slowed down with shearing cycles.The normal displacement experienced a slight increase before shear sliding due to deformation recovery as the unloading stress was unloaded,and then enhanced shear dilation after sliding initiation due to climbing effects of surface asperities.Dilation was positively related to the shear sliding velocity of fractures.Wear characteristics of the fracture surfaces after shearing failure were evaluated using binary calculation,indicating an increasing shear area ratio by 45.24%e91.02%with normal stress.

Surface Roughness Around a 325-m Meteorological Tower and Its Effect on Urban Turbulence

Based on slow- and fast-response measurements under neutral stratification conditions from a 325-m meteorological tower located in a built-up area of north-central Beijing as well as a descriptive survey of surface roughness elements (i.e., buildings and trees) around the tower site, urban roughness lengths, zo, with zero-plane displacement height are estimated using logarithmic wind profile and morphometric methods in eight 45° directional sectors. When comparing their results with each other, the slow-response method tends to give smaller zo values. At a given location, considerable directional variations in values are observed. The effect of surface roughness on urban turbulence characteristics in terms of non-dimensional standard deviations of three-component velocity, σi/u*1 (where i = u, v, w and u*1 is local friction velocity), is investigated.

Experimental study of evaporation of sessile water droplet on PDMS surfaces

Evaporation of sessile water droplet on polydimethylsiloxane （PDMS） surfaces with three different curing ratios （5：1, 10：1, and 20：1） was experimentally investigated in this paper. We show that the constant contact radius （CCR） evaporation on surface with high curing ratio lasts longer than that with low curing ratio. We also measured Young＇s moduli of PDMS films by using atomic force microscopy （AFM） and simulated surface deformation of PDMS films induced by sessile water droplet. With increasing curing ratio of PDMS film, Young＇s modulus of PDMS film is getting lower, and then there will be larger surface deformation and more elastic stored energy. Since such energy acts as a barrier to keep the three-phase contact line pinned, thus it will result in longer CCR evaporation on PDMS surface with higher curing ratio.

特大型顺层古滑坡复活变形特征分析及变形预测研究

为有效掌握古滑坡复活特征及其变形规律,基于滑坡区现场调查成果,首先开展其复活变形特征分析,再利用WPT-ROA-RVM-CT模型进行滑坡变形预测研究。结果表明,在强降雨或持续降雨后,滑坡地表裂缝较为发育,具有张剪性质,且滑坡呈明显推移式特征,即滑坡中、后缘变形明显大于前缘,变形方向具有逆时针变化规律,充分说明古滑坡复活变形特征显著。同时,通过变形预测,验证WPT-ROA-RVM-CT模型具有较高的预测精度,并经外推预测,得到滑坡后续变形速率均为正值且较大,判断滑坡后续变形还会进一步增加,具有较大失稳风险,需尽快开展灾害防治研究。

三峡库区万州金金子滑坡稳定性分析

三峡库区两岸斜坡受库水位变化及降雨等影响,极易诱发滑坡灾害。万州金金子滑坡是三峡库区典型涉水型滑坡,滑坡体自2003年三峡大坝蓄水以来持续变形,2016年滑坡体发生了局部变形破坏。基于现场地质调查及工程地质钻探,结合GPS地表位移监测数据,分析了滑坡体变形特征;利用Geostu-dio软件进行敏感性数值分析,结合滑坡稳定性计算对其变形发展的趋势进行了预测。结果表明:在强降雨条件下,金金子滑坡整体虽处于稳定状态,但其强变形区因降雨导致滑带土的抗剪强度降低和滑坡体容重增加,从而加大滑坡体的下滑力,使滑坡体产生变形,滑坡面径流使滑坡体下滑力进一步增大,从而导致强变形区失稳破坏。

Dynamic Response and Deformation Behavior of Kadui-2 Landslide Influenced by Reservoir Impoundment and Rainfall,Baoxing,China

This study focuses on the deformation characteristics of Kadui-2 Landslide by the influence of reservoir filling-drawdown and precipitation.A three-year monitoring project was implemented in order to observe the short/long-term deformation.The slide mass experienced consistent deformation with a maximum cumulative displacement of 331.34 cm.Based on the recorded data of reservoir water level and precipitation during this period,a two-dimensional(2-D)finite element model using Geostudio software was set up for deformation simulation under different conditions to understand the real influence of these triggering factors on landslide.The numerical simulation results are in consistent with monitoring field data.Both numerical simulation and field monitoring results exhibit that the maximum deformation occurred at the foreside of slumping mass.The slip surface shows significant creep characteristics decreasing as long-term shear strength reducing gradually.Reservoir water level fluctuation is the primary triggering factor to reactivate the landslide mass and has a negative correlation with deformation rate.Displacement rate increases with the reservoir drawdown and decreases with impoundment rise.Compared with reservoir filling-drawdown operation,rainfall has no significant effect on the slide motion of landslide due to limited penetration from the ground surface.

充填法开采对主要井巷和地表构建筑物稳定性影响的数值模拟研究

地下采矿活动导致的地面沉降直接威胁到矿区的安全运行。依托于实际矿山,探究地下开采过程中对井巷工程及地表构筑物稳定性的影响。通过实验室测试与Hoek-Brown岩石强度标准来确定岩石的力学性质,并构建了一个三维数值模型,使用FLAC 3D软件对地下开采引起的地面形变进行了模拟分析,计算出了最大地面沉降位移、倾斜率、曲率和水平形变等关键参数。研究发现,这些参数的数值都低于标准规定的安全值,表明地面结构比较稳定和安全。

土工格栅加筋路堤变形模拟分析

为分析不同土工格栅加筋方案对路堤变形的影响,制定了路堤一级边坡、一二级边坡之间和二级边坡三个位置共八种加筋方案,通过建立计算模型进行数值模拟分析,确定路堤不同位置最优加筋方案。通过对比分析,得到各方案对路堤内部竖向位移和坡面水平位移的控制效果,并分析确定方案八为最优加筋方案。

双山煤矿地表移动变形实测规律分析

为探究双山煤矿综放开采地表岩移规律,以308综放工作面为研究对象,通过对其地表观测数据的分析,给出双山煤矿工作面综放开采地表移动变形规律和相关地表岩移参数,结合工作面开采地表沉陷及损害情况对双山煤矿综放工作面开采地表移动变形过程进行分析。研究表明,地表各测点连续6个月的累计下沉值均小于30 mm时地表移动达到稳定状态,即下沉速度降低至0.17 mm/d。根据地表最大下沉平均速度的下降趋势,判断目前地表移动趋于稳定,按照下沉速度下降趋势,可推断5个月后308综放工作面地表下沉可达稳定状态。实测数据经计算分析得出超前影响角,可为矿区今后的地下开采及安全煤柱留设提供依据。

某高速公路“充填式”滑坡变形特征分析

“充填式”滑坡是指古沟谷地貌被新沉积物充填覆盖,在开挖影响下,充填物沿新老界面发生滑动而形成的滑坡。本文研究对象为浅挖路段,地形平坦,最大挖深约17 m,开挖后两侧边坡土石界面呈典型的“V”字形,后缘约200 m处出现拉张裂缝,初步判断滑坡位于古河道上。为准确查明滑坡特征,在物探和钻探的基础上采用深部位移监测手段。结果表明,滑坡目前处于蠕滑阶段;滑坡前缘滑动面为土石界面,后段为风化岩层,滑动面与地下水位线基本一致,并非完全沿充填物界面发生破坏。

黄河冲积地层临河深基坑变形特性研究

依据黄河冲积地层某采用地下连续墙加内支撑支护结构的临河深基坑开挖监测数据,研究了地下连续墙墙体水平位移、地下连续墙墙顶竖向位移和地下连续墙墙后地表沉降的变化规律,验证了采用稳定安全系数法估算深基坑变形在该地区的适用性。研究结果表明:地下连续墙墙体水平位移具有显著的时空效应,墙体最大水平位移随监测点与深基坑边缘距离的增大呈对数型增长趋势,墙体最大水平位移与深基坑开挖深度成线性正相关;底板浇筑前地下连续墙墙体最大水平位移为0.15%H(H为基坑总深度),位于92.3%H深度处。地下连续墙墙顶竖向隆起,底板浇筑后土体自重应力获得一定程度的恢复,地下连续墙墙顶竖向位移基本保持稳定。地下连续墙墙后地表沉降呈凹槽形分布,墙后最大地表沉降为0.11%H。采用稳定安全系数法估算地下连续墙墙体最大水平位移为0.38%H,地下连续墙墙后最大地表沉降实测值为地下连续墙墙体最大水平位移实测值的73%,符合稳定安全系数法估算结果,可为类似地区深基坑变形特性研究提供参考。

相邻基坑同步施工对围护结构受力变形的影响实例研究

相邻深基坑同步开挖施工对围护结构体系受力和变形的影响尚不明确。通过对同步施工的某建筑物深大基坑与相邻地铁车站基坑进行监测,对比分析了相邻部位和非相邻部位围护结构顶部位移、水平支撑轴力、深层土体水平位移、地表沉降以及地下水位等的变化。监测结果表明:(1)当车站基坑开挖深度较浅时,建筑基坑相邻部位桩因两侧土压不平衡导致桩顶向坑外侧移而竖向位移出现“上浮”现象,但是,当车站基坑开挖深度超过建筑基坑深度时,建筑基坑相邻部位桩桩顶水平位移转向坑内加剧发展而竖向位移出现“回落”现象;(2)受邻近基坑卸载影响,建筑基坑水平支撑轴力将减小;(3)两基坑间地表沉降大于非相邻部位,且地表沉降变化与桩顶位移和地下水位变化相关联;(4)相邻部位基坑壁深层土体水平位移有向坑外变形的趋势。

杭来湾煤矿大采高综采面回采巷道围岩变形规律

回采巷道超前段围岩变形规律对于评价和优化巷道支护技术和保证工作面正常生产具有重要意义。以杭来湾煤矿30201大采高工作面为例,采用十字观测法对30201工作面回采巷道超前段表面位移变化规律进行监测,发现胶运平巷在超前工作面约22~38 m处开始发生变形,顶底板、两帮移近速度分别从11~15 m处急剧增大。同时,采用钻孔窥视技术对胶运平巷超前段围岩松动圈分布情况进行了观测,发现工作面前方3 m处巷道围岩处于采动影响剧烈阶段,工作面前方8 m处于超前支承压力峰值影响阶段,工作面前方18 m处处于超前支承压力减弱段。综合分析表面位移变形规律和松动圈测试结果,30201回采巷道采动影响迹象显现范围约为超前18 m。该成果可为类似大采高工作面回采巷道围岩控制及支护参数优化提供借鉴。

T型地下连续墙基坑支护特性研究

通过对T型地下连续墙受力及支护特征研究分析,结合等效刚度原理,采用弹性地基梁法对墙体内力及位移进行推导;采用理论计算、数值分析等方法,建立T型地下连续墙基坑支护三维有限元模型,分析基坑开挖过程中不同开挖深度及不同截面处的墙体水平位移、墙后地表沉降规律。结果表明:采用T型地下连续墙进行基坑支护时,墙边至肋端外侧1/3~1/2肋长范围土体变形受墙肋影响较大;T型地下连续墙对于较大开挖深度能够更早起到支护作用,对于较小的开挖深度作用有限;墙厚增加将降低墙体变形,但在一定开挖深度下,存在最优墙厚,在满足基坑变形要求的前提下,可适当减小墙厚,以提高工程经济性。

基于应力与位移分析的地表沉陷区圈定

地表沉陷区是判定地表建(构)筑物稳定性的重要依据,一般认为沉陷区内地表的下沉值较大,不利于建(构)筑物稳定。充分采动时通常在垂直和平行矿体走向的主断面上,从采空区边界按照查手册确定的地表移动角向地表绘出矿体两侧的地表临界变形点,再连接这些临界变形点形成地表移动区。不充分采动或充填法采矿时还没有地表移动区的圈定方法,只能沿用充分采动的圈定方法,导致圈定的范围过大或评价结论不可靠。基于房柱式留矿法对地表滑坡影响的理论分析和数值模拟,得出不充分采动时绘制地表移动区的启示,并结合充填采矿的地压规律研究,探讨了充填采矿的地表移动区绘制方法。结果表明:充填采矿时应根据主断面开采的应力与位移分析确定地表沉陷区绘制的参考面及地表移动角;附近几乎受拉或地压与原岩应力区别很大的位移等值线与水平面所成的角应为地表移动角,否则,根据附近不受拉或处于原岩应力状态的位移等值线确定的移动角偏小,圈定的地表沉陷区过大;主断面内位移变化明显的平面应为参考面,如矿柱稠密或充填法采矿时最顶部采场的顶板。

地铁车站明挖深基坑围护结构变形规律分析

以绍兴地铁2号线车站基坑工程为实例,通过对地连墙水平位移、支撑轴力、地表沉降现场监测数据的分析,得到绍兴地区基坑工程围护结构的相关变形规律并给出相应的控制措施。结果表明:墙体水平位移基本呈内凸型模式,最大侧移在40~60 mm之间,基坑地表沉降呈凹槽形模式,其地表沉降主要集中在50~80 mm左右。地连墙最大侧移δ_(hm)在(0.05%,0.37%)H范围内,平均值为0.21%H;地下连续墙最大侧移点埋深δ_(hm)主要落于(0.69%,0.94%)H范围内;墙后最大地表沉降δ_(hm)范围在(0.01%,0.5%)H内,平均值为0.26%H。

基于3D-DIC系统的白砂岩单轴压缩应变率效应的力学性能试验研究

通过选取典型岩样,研究了白砂岩在10^(-5)~10^(-3)s^(-1)应变率范围内的单轴压缩性能,采用3D-DIC系统观测和采集岩样表面位移云图,并分析不同应变率下岩样变形破坏特征差异。结果表明,岩样表面位移场变化反映了破坏面演化规律,剪切破坏面与位移场集中存在对应关系。全局轴向应变差异主要发生在微裂隙压密到弹性变形期间;加载初期,全局径向应变存在差异,在峰值强度时下端部区域径向位移最大,岩样上端部变形受到端部效应影响,径向向外膨胀受端面与垫片间摩擦限制;此外,下端部局部轴向应变大于上端部区域。随着加载速率增大,岩样从延性特征向脆性特征转变。加载速率较低时,岩样破坏过程中孔隙坍塌使得部分裂隙再次闭合、滑移而产生摩擦效应,从而使峰值强度附近的应力-应变曲线出现波动。白砂岩峰值强度、弹性模量、泊松比等力学参数随加载速率增大而增加。

大厚度夯填黄土场地工后变形特性研究

以陕北某黄土沟壑区高填方黄土场地为例,利用多重监测手段对填方体进行了长期、连续的变形监测,利用监测成果分别研究了夯填黄土场地地表和深部的沉降变形及水平位移变形特性。对影响沉降变形的压缩层厚度因素及时间因素进行分析,建立多因素沉降变形回归模型,讨论了以沉降变形速率作为稳定标准,不同填方厚度条件下的填方体沉降变形稳定时间。分析表明:分层强夯回填黄土场地的最终工后沉降量约为压缩层厚度的1.29‰,填方体的地表水平位移量较沉降变形量小,地表水平位移变形在方向上指向填方体临空面方向或填土厚度较大部位方向;在深层变形特性上,填方体表现出表层回弹、深部压缩的变形特性,填方体的深层水平位移表现出呈随深度减小的趋势。